Improve video key frame sending.

This change does not include the addition of VP9. We do that in a
separate pull request.

Changes:

* fix the video bug (video frames larger than 65KBytes) by sending full
  frame length in alternate header field
* improve video frame reconstruction logic with slots
* configure video encoder and decoder to be multihtreaded
* set error resilience flags on video codec
* change encoder and decoder softdeadline

11 files changed, 1031 insertions, 406 deletions

diff --git a/testing/BUILD.bazel b/testing/BUILD.bazel
index afb1a8aa..6cc7018e 100644
--- a/testing/BUILD.bazel
+++ b/testing/BUILD.bazel
@@ -34,9 +34,9 @@ cc_binary(
         "//c-toxcore/toxav",
         "//c-toxcore/toxav:monolith",
         "//c-toxcore/toxcore",
-        "@portaudio",
-        "@sndfile",
         "@opencv//:core",
         "@opencv//:highgui",
+        "@portaudio",
+        "@sndfile",
     ],
 )
diff --git a/toxav/BUILD.bazel b/toxav/BUILD.bazel
index ff775fdd..cf905910 100644
--- a/toxav/BUILD.bazel
+++ b/toxav/BUILD.bazel
@@ -41,7 +41,7 @@ cc_test(
     deps = [
         ":rtp",
         "//c-toxcore/toxcore:crypto_core",
-        "@gtest",
+        "@com_google_googletest//:gtest_main",
     ],
 )
 
diff --git a/toxav/bwcontroller.c b/toxav/bwcontroller.c
index 9d1ad9ce..defb3fde 100644
--- a/toxav/bwcontroller.c
+++ b/toxav/bwcontroller.c
@@ -32,9 +32,10 @@
 #include <errno.h>
 
 #define BWC_PACKET_ID 196
-#define BWC_SEND_INTERVAL_MS 1000
-#define BWC_REFRESH_INTERVAL_MS 10000
+#define BWC_SEND_INTERVAL_MS 950     /* 0.95s  */
+#define BWC_REFRESH_INTERVAL_MS 2000 /* 2.00s */
 #define BWC_AVG_PKT_COUNT 20
+#define BWC_AVG_LOSS_OVER_CYCLES_COUNT 30
 
 struct BWController_s {
     void (*mcb)(BWController *, uint32_t, float, void *);
@@ -56,6 +57,8 @@ struct BWController_s {
         uint32_t packet_length_array[BWC_AVG_PKT_COUNT];
         RingBuffer *rb;
     } rcvpkt; /* To calculate average received packet (this means split parts, not the full message!) */
+
+    uint32_t packet_loss_counted_cycles;
 };
 
 struct BWCMessage {
@@ -71,23 +74,23 @@ BWController *bwc_new(Messenger *m, uint32_t friendnumber,
                       void *udata)
 {
     BWController *retu = (BWController *)calloc(sizeof(struct BWController_s), 1);
-
+    LOGGER_DEBUG(m->log, "Creating bandwidth controller");
     retu->mcb = mcb;
     retu->mcb_data = udata;
     retu->m = m;
     retu->friend_number = friendnumber;
     retu->cycle.last_sent_timestamp = retu->cycle.last_refresh_timestamp = current_time_monotonic();
     retu->rcvpkt.rb = rb_new(BWC_AVG_PKT_COUNT);
+    retu->cycle.lost = 0;
+    retu->cycle.recv = 0;
+    retu->packet_loss_counted_cycles = 0;
 
     /* Fill with zeros */
-    int i = 0;
-
-    for (; i < BWC_AVG_PKT_COUNT; i ++) {
-        rb_write(retu->rcvpkt.rb, retu->rcvpkt.packet_length_array + i);
+    for (int i = 0; i < BWC_AVG_PKT_COUNT; i++) {
+        rb_write(retu->rcvpkt.rb, &retu->rcvpkt.packet_length_array[i]);
     }
 
     m_callback_rtp_packet(m, friendnumber, BWC_PACKET_ID, bwc_handle_data, retu);
-
     return retu;
 }
 
@@ -98,47 +101,21 @@ void bwc_kill(BWController *bwc)
     }
 
     m_callback_rtp_packet(bwc->m, bwc->friend_number, BWC_PACKET_ID, nullptr, nullptr);
-
     rb_kill(bwc->rcvpkt.rb);
     free(bwc);
 }
 
-void bwc_feed_avg(BWController *bwc, uint32_t bytes)
-{
-    uint32_t *p;
-
-    rb_read(bwc->rcvpkt.rb, (void **) &p);
-    rb_write(bwc->rcvpkt.rb, p);
-
-    *p = bytes;
-}
-
 void bwc_add_lost(BWController *bwc, uint32_t bytes_lost)
 {
     if (!bwc) {
         return;
     }
 
-    if (!bytes_lost) {
-        uint32_t *t_avg[BWC_AVG_PKT_COUNT], c = 1;
-
-        rb_data(bwc->rcvpkt.rb, (void **) t_avg);
-
-        int i = 0;
-
-        for (; i < BWC_AVG_PKT_COUNT; i ++) {
-            bytes_lost += *(t_avg[i]);
-
-            if (*(t_avg[i])) {
-                c++;
-            }
-        }
-
-        bytes_lost /= c;
+    if (bytes_lost > 0) {
+        LOGGER_DEBUG(bwc->m->log, "BWC lost(1): %d", (int)bytes_lost);
+        bwc->cycle.lost += bytes_lost;
+        send_update(bwc);
     }
-
-    bwc->cycle.lost += bytes_lost;
-    send_update(bwc);
 }
 
 void bwc_add_recv(BWController *bwc, uint32_t recv_bytes)
@@ -147,37 +124,35 @@ void bwc_add_recv(BWController *bwc, uint32_t recv_bytes)
         return;
     }
 
+    bwc->packet_loss_counted_cycles++;
     bwc->cycle.recv += recv_bytes;
     send_update(bwc);
 }
 
-
 void send_update(BWController *bwc)
 {
-    if (current_time_monotonic() - bwc->cycle.last_refresh_timestamp > BWC_REFRESH_INTERVAL_MS) {
-
-        bwc->cycle.lost /= 10;
-        bwc->cycle.recv /= 10;
-        bwc->cycle.last_refresh_timestamp = current_time_monotonic();
-    } else if (current_time_monotonic() - bwc->cycle.last_sent_timestamp > BWC_SEND_INTERVAL_MS) {
+    if (bwc->packet_loss_counted_cycles > BWC_AVG_LOSS_OVER_CYCLES_COUNT &&
+            current_time_monotonic() - bwc->cycle.last_sent_timestamp > BWC_SEND_INTERVAL_MS) {
+        bwc->packet_loss_counted_cycles = 0;
 
         if (bwc->cycle.lost) {
-            LOGGER_DEBUG(bwc->m->log, "%p Sent update rcv: %u lost: %u",
-                         bwc, bwc->cycle.recv, bwc->cycle.lost);
-
-            uint8_t p_msg[sizeof(struct BWCMessage) + 1];
-            struct BWCMessage *b_msg = (struct BWCMessage *)(p_msg + 1);
-
-            p_msg[0] = BWC_PACKET_ID;
-            b_msg->lost = net_htonl(bwc->cycle.lost);
-            b_msg->recv = net_htonl(bwc->cycle.recv);
-
-            if (-1 == m_send_custom_lossy_packet(bwc->m, bwc->friend_number, p_msg, sizeof(p_msg))) {
-                LOGGER_WARNING(bwc->m->log, "BWC send failed (len: %d)! std error: %s", sizeof(p_msg), strerror(errno));
+            LOGGER_DEBUG(bwc->m->log, "%p Sent update rcv: %u lost: %u percent: %f %%",
+                         bwc, bwc->cycle.recv, bwc->cycle.lost,
+                         (((float) bwc->cycle.lost / (bwc->cycle.recv + bwc->cycle.lost)) * 100.0f));
+            uint8_t bwc_packet[sizeof(struct BWCMessage) + 1];
+            struct BWCMessage *msg = (struct BWCMessage *)(bwc_packet + 1);
+            bwc_packet[0] = BWC_PACKET_ID; // set packet ID
+            msg->lost = net_htonl(bwc->cycle.lost);
+            msg->recv = net_htonl(bwc->cycle.recv);
+
+            if (-1 == m_send_custom_lossy_packet(bwc->m, bwc->friend_number, bwc_packet, sizeof(bwc_packet))) {
+                LOGGER_WARNING(bwc->m->log, "BWC send failed (len: %d)! std error: %s", sizeof(bwc_packet), strerror(errno));
             }
         }
 
         bwc->cycle.last_sent_timestamp = current_time_monotonic();
+        bwc->cycle.lost = 0;
+        bwc->cycle.recv = 0;
     }
 }
 
@@ -185,9 +160,9 @@ static int on_update(BWController *bwc, const struct BWCMessage *msg)
 {
     LOGGER_DEBUG(bwc->m->log, "%p Got update from peer", bwc);
 
-    /* Peer must respect time boundary */
-    if (current_time_monotonic() < bwc->cycle.last_recv_timestamp + BWC_SEND_INTERVAL_MS) {
-        LOGGER_DEBUG(bwc->m->log, "%p Rejecting extra update", bwc);
+    /* Peers sent update too soon */
+    if (bwc->cycle.last_recv_timestamp + BWC_SEND_INTERVAL_MS > current_time_monotonic()) {
+        LOGGER_INFO(bwc->m->log, "%p Rejecting extra update", bwc);
         return -1;
     }
 
@@ -196,9 +171,9 @@ static int on_update(BWController *bwc, const struct BWCMessage *msg)
     uint32_t recv = net_ntohl(msg->recv);
     uint32_t lost = net_ntohl(msg->lost);
 
-    LOGGER_DEBUG(bwc->m->log, "recved: %u lost: %u", recv, lost);
-
     if (lost && bwc->mcb) {
+        LOGGER_DEBUG(bwc->m->log, "recved: %u lost: %u percentage: %f %%", recv, lost,
+                     (((float) lost / (recv + lost)) * 100.0f));
         bwc->mcb(bwc, bwc->friend_number,
                  ((float) lost / (recv + lost)),
                  bwc->mcb_data);
diff --git a/toxav/bwcontroller.h b/toxav/bwcontroller.h
index 43475252..be5eb191 100644
--- a/toxav/bwcontroller.h
+++ b/toxav/bwcontroller.h
@@ -27,9 +27,9 @@ typedef struct BWController_s BWController;
 BWController *bwc_new(Messenger *m, uint32_t friendnumber,
                       void (*mcb)(BWController *, uint32_t, float, void *),
                       void *udata);
+
 void bwc_kill(BWController *bwc);
 
-void bwc_feed_avg(BWController *bwc, uint32_t bytes);
 void bwc_add_lost(BWController *bwc, uint32_t bytes);
 void bwc_add_recv(BWController *bwc, uint32_t bytes);
 
diff --git a/toxav/rtp.c b/toxav/rtp.c
index 06bc6df5..c5d940e2 100644
--- a/toxav/rtp.c
+++ b/toxav/rtp.c
@@ -33,11 +33,557 @@
 #include <errno.h>
 #include <stdlib.h>
 
+enum {
+    /**
+     * The number of milliseconds we want to keep a keyframe in the buffer for,
+     * even though there are no free slots for incoming frames.
+     */
+    VIDEO_KEEP_KEYFRAME_IN_BUFFER_FOR_MS = 15,
+};
+
+// allocate_len is NOT including header!
+static struct RTPMessage *new_message(const struct RTPHeader *header, size_t allocate_len, const uint8_t *data,
+                                      uint16_t data_length)
+{
+    assert(allocate_len >= data_length);
+    struct RTPMessage *msg = (struct RTPMessage *)calloc(1, sizeof(struct RTPMessage) + allocate_len);
+
+    if (msg == nullptr) {
+        return nullptr;
+    }
+
+    msg->len = data_length; // result without header
+    msg->header = *header;
+    memcpy(msg->data, data, msg->len);
+    return msg;
+}
+
+enum {
+    /**
+     * Instruct the caller to clear slot 0.
+     */
+    GET_SLOT_RESULT_DROP_OLDEST_SLOT = -1,
+    /**
+     * Instruct the caller to drop the incoming packet.
+     */
+    GET_SLOT_RESULT_DROP_INCOMING = -2,
+};
+
+/**
+ * Find the next free slot in work_buffer for the incoming data packet.
+ *
+ * - If the data packet belongs to a frame thats already in the work_buffer then
+ *   use that slot.
+ * - If there is no free slot return GET_SLOT_RESULT_DROP_OLDEST_SLOT.
+ * - If the data packet is too old return GET_SLOT_RESULT_DROP_INCOMING.
+ *
+ * If there is a keyframe beeing assembled in slot 0, keep it a bit longer and
+ * do not kick it out right away if all slots are full instead kick out the new
+ * incoming interframe.
+ */
+static int8_t get_slot(Logger *log, struct RTPWorkBufferList *wkbl, bool is_keyframe,
+                       const struct RTPHeader *header, bool is_multipart)
+{
+    if (is_multipart) {
+        // This RTP message is part of a multipart frame, so we try to find an
+        // existing slot with the previous parts of the frame in it.
+        for (uint8_t i = 0; i < wkbl->next_free_entry; i++) {
+            const struct RTPWorkBuffer *slot = &wkbl->work_buffer[i];
+
+            if ((slot->buf->header.sequnum == header->sequnum) && (slot->buf->header.timestamp == header->timestamp)) {
+                // Sequence number and timestamp match, so this slot belongs to
+                // the same frame.
+                //
+                // In reality, these will almost certainly either both match or
+                // both not match. Only if somehow there were 65535 frames
+                // between, the timestamp will matter.
+                return i;
+            }
+        }
+    }
+
+    // The message may or may not be part of a multipart frame.
+    //
+    // If it is part of a multipart frame, then this is an entirely new frame
+    // for which we did not have a slot *or* the frame is so old that its slot
+    // has been evicted by now.
+    //
+    //        |----------- time ----------->
+    //        _________________
+    // slot 0 |               |
+    //        -----------------
+    //                     _________________
+    // slot 1              |               |
+    //                     -----------------
+    //                ____________
+    // slot 2         |          | -> frame too old, drop
+    //                ------------
+    //
+    //
+    //
+    //        |----------- time ----------->
+    //        _________________
+    // slot 0 |               |
+    //        -----------------
+    //                     _________________
+    // slot 1              |               |
+    //                     -----------------
+    //                              ____________
+    // slot 2                       |          | -> ok, start filling in a new slot
+    //                              ------------
+
+    // If there is a free slot:
+    if (wkbl->next_free_entry < USED_RTP_WORKBUFFER_COUNT) {
+        // If there is at least one filled slot:
+        if (wkbl->next_free_entry > 0) {
+            // Get the most recently filled slot.
+            const struct RTPWorkBuffer *slot = &wkbl->work_buffer[wkbl->next_free_entry - 1];
+
+            // If the incoming packet is older than our newest slot, drop it.
+            // This is the first situation in the above diagram.
+            if (slot->buf->header.timestamp > header->timestamp) {
+                LOGGER_DEBUG(log, "workbuffer:2:timestamp too old");
+                return GET_SLOT_RESULT_DROP_INCOMING;
+            }
+        }
+
+        // Not all slots are filled, and the packet is newer than our most
+        // recent slot, so it's a new frame we want to start assembling. This is
+        // the second situation in the above diagram.
+        return wkbl->next_free_entry;
+    }
+
+    // If the incoming frame is a key frame, then stop assembling the oldest
+    // slot, regardless of whether there was a keyframe in that or not.
+    if (is_keyframe) {
+        return GET_SLOT_RESULT_DROP_OLDEST_SLOT;
+    }
+
+    // The incoming slot is not a key frame, so we look at slot 0 to see what to
+    // do next.
+    const struct RTPWorkBuffer *slot = &wkbl->work_buffer[0];
+
+    // The incoming frame is not a key frame, but the existing slot 0 is also
+    // not a keyframe, so we stop assembling the existing frame and make space
+    // for the new one.
+    if (!slot->is_keyframe) {
+        return GET_SLOT_RESULT_DROP_OLDEST_SLOT;
+    }
+
+    // If this key frame is fully received, we also stop assembling and clear
+    // slot 0.  This also means sending the frame to the decoder.
+    if (slot->received_len == slot->buf->header.data_length_full) {
+        return GET_SLOT_RESULT_DROP_OLDEST_SLOT;
+    }
+
+    // This is a key frame, not fully received yet, but it's already much older
+    // than the incoming frame, so we stop assembling it and send whatever part
+    // we did receive to the decoder.
+    if (slot->buf->header.timestamp + VIDEO_KEEP_KEYFRAME_IN_BUFFER_FOR_MS <= header->timestamp) {
+        return GET_SLOT_RESULT_DROP_OLDEST_SLOT;
+    }
+
+    // This is a key frame, it's not too old yet, so we keep it in its slot for
+    // a little longer.
+    LOGGER_INFO(log, "keep KEYFRAME in workbuffer");
+    return GET_SLOT_RESULT_DROP_INCOMING;
+}
+
+/**
+ * Returns an assembled frame (as much data as we currently have for this frame,
+ * some pieces may be missing)
+ *
+ * If there are no frames ready, we return NULL. If this function returns
+ * non-NULL, it transfers ownership of the message to the caller, i.e. the
+ * caller is responsible for storing it elsewhere or calling free().
+ */
+static struct RTPMessage *process_frame(Logger *log, struct RTPWorkBufferList *wkbl, uint8_t slot_id)
+{
+    assert(wkbl->next_free_entry >= 0);
+
+    if (wkbl->next_free_entry == 0) {
+        // There are no frames in any slot.
+        return nullptr;
+    }
+
+    // Slot 0 contains a key frame, slot_id points at an interframe that is
+    // relative to that key frame, so we don't use it yet.
+    if (wkbl->work_buffer[0].is_keyframe && slot_id != 0) {
+        LOGGER_DEBUG(log, "process_frame:KEYFRAME waiting in slot 0");
+        return nullptr;
+    }
+
+    // Either slot_id is 0 and slot 0 is a key frame, or there is no key frame
+    // in slot 0 (and slot_id is anything).
+    struct RTPWorkBuffer *const slot = &wkbl->work_buffer[slot_id];
+
+    // Move ownership of the frame out of the slot into m_new.
+    struct RTPMessage *const m_new = slot->buf;
+    slot->buf = nullptr;
+
+    assert(wkbl->next_free_entry >= 1);
+
+    if (slot_id != wkbl->next_free_entry - 1) {
+        // The slot is not the last slot, so we created a gap. We move all the
+        // entries after it one step up.
+        for (uint8_t i = slot_id; i < wkbl->next_free_entry - 1; i++) {
+            // Move entry (i+1) into entry (i).
+            wkbl->work_buffer[i] = wkbl->work_buffer[i + 1];
+        }
+    }
+
+    // We now have a free entry at the end of the array.
+    wkbl->next_free_entry--;
+
+    // Clear the newly freed entry.
+    const struct RTPWorkBuffer empty = {0};
+    wkbl->work_buffer[wkbl->next_free_entry] = empty;
+
+    // Move ownership of the frame to the caller.
+    return m_new;
+}
+
+/**
+ * @param log A logger.
+ * @param wkbl The list of in-progress frames, i.e. all the slots.
+ * @param slot_id The slot we want to fill the data into.
+ * @param is_keyframe Whether the data is part of a key frame.
+ * @param header The RTP header from the incoming packet.
+ * @param incoming_data The pure payload without header.
+ * @param incoming_data_length The length in bytes of the incoming data payload.
+ */
+static bool fill_data_into_slot(Logger *log, struct RTPWorkBufferList *wkbl, const uint8_t slot_id, bool is_keyframe,
+                                const struct RTPHeader *header, const uint8_t *incoming_data, uint16_t incoming_data_length)
+{
+    // We're either filling the data into an existing slot, or in a new one that
+    // is the next free entry.
+    assert(slot_id <= wkbl->next_free_entry);
+    struct RTPWorkBuffer *const slot = &wkbl->work_buffer[slot_id];
+
+    assert(header != nullptr);
+    assert(is_keyframe == (bool)(header->flags & RTP_KEY_FRAME));
+
+    if (slot->received_len == 0) {
+        assert(slot->buf == nullptr);
+
+        // No data for this slot has been received, yet, so we create a new
+        // message for it with enough memory for the entire frame.
+        struct RTPMessage *msg = (struct RTPMessage *)calloc(1, sizeof(struct RTPMessage) + header->data_length_full);
+
+        if (msg == nullptr) {
+            LOGGER_ERROR(log, "Out of memory while trying to allocate for frame of size %u\n",
+                         (unsigned)header->data_length_full);
+            // Out of memory: throw away the incoming data.
+            return false;
+        }
+
+        // Unused in the new video receiving code, as it's 16 bit and can't hold
+        // the full length of large frames. Instead, we use slot->received_len.
+        msg->len = 0;
+        msg->header = *header;
+
+        slot->buf = msg;
+        slot->is_keyframe = is_keyframe;
+        slot->received_len = 0;
+
+        assert(wkbl->next_free_entry < USED_RTP_WORKBUFFER_COUNT);
+        wkbl->next_free_entry++;
+    }
+
+    // We already checked this when we received the packet, but we rely on it
+    // here, so assert again.
+    assert(header->offset_full < header->data_length_full);
+
+    // Copy the incoming chunk of data into the correct position in the full
+    // frame data array.
+    memcpy(
+        slot->buf->data + header->offset_full,
+        incoming_data,
+        incoming_data_length
+    );
+
+    // Update the total received length of this slot.
+    slot->received_len += incoming_data_length;
+
+    // Update received length also in the header of the message, for later use.
+    slot->buf->header.received_length_full = slot->received_len;
+
+    return slot->received_len == header->data_length_full;
+}
+
+static void update_bwc_values(Logger *log, RTPSession *session, const struct RTPMessage *msg)
+{
+    if (session->first_packets_counter < DISMISS_FIRST_LOST_VIDEO_PACKET_COUNT) {
+        session->first_packets_counter++;
+    } else {
+        uint32_t data_length_full = msg->header.data_length_full; // without header
+        uint32_t received_length_full = msg->header.received_length_full; // without header
+        bwc_add_recv(session->bwc, data_length_full);
+
+        if (received_length_full < data_length_full) {
+            LOGGER_DEBUG(log, "BWC: full length=%u received length=%d", data_length_full, received_length_full);
+            bwc_add_lost(session->bwc, (data_length_full - received_length_full));
+        }
+    }
+}
+
+/**
+ * Handle a single RTP video packet.
+ *
+ * The packet may or may not be part of a multipart frame. This function will
+ * find out and handle it appropriately.
+ *
+ * @param session The current RTP session with:
+ *   session->mcb == vc_queue_message() // this function is called from here
+ *   session->mp == struct RTPMessage *
+ *   session->cs == call->video.second // == VCSession created by vc_new() call
+ * @param header The RTP header deserialised from the packet.
+ * @param incoming_data The packet data *not* header, i.e. this is the actual
+ *   payload.
+ * @param incoming_data_length The packet length *not* including header, i.e.
+ *   this is the actual payload length.
+ * @param log A logger.
+ *
+ * @return -1 on error, 0 on success.
+ */
+static int handle_video_packet(RTPSession *session, const struct RTPHeader *header,
+                               const uint8_t *incoming_data, uint16_t incoming_data_length, Logger *log)
+{
+    // Full frame length in bytes. The frame may be split into multiple packets,
+    // but this value is the complete assembled frame size.
+    const uint32_t full_frame_length = header->data_length_full;
+
+    // Current offset in the frame. If this is the first packet of a multipart
+    // frame or it's not a multipart frame, then this value is 0.
+    const uint32_t offset = header->offset_full; // without header
+
+    // The sender tells us whether this is a key frame.
+    const bool is_keyframe = (header->flags & RTP_KEY_FRAME) != 0;
+
+    LOGGER_DEBUG(log, "-- handle_video_packet -- full lens=%u len=%u offset=%u is_keyframe=%s",
+                 (unsigned)incoming_data_length, (unsigned)full_frame_length, (unsigned)offset, is_keyframe ? "K" : ".");
+    LOGGER_DEBUG(log, "wkbl->next_free_entry:003=%d", session->work_buffer_list->next_free_entry);
+
+    const bool is_multipart = full_frame_length != incoming_data_length;
+
+    /* The message was sent in single part */
+    int8_t slot_id = get_slot(log, session->work_buffer_list, is_keyframe, header, is_multipart);
+    LOGGER_DEBUG(log, "slot num=%d", slot_id);
+
+    // get_slot told us to drop the packet, so we ignore it.
+    if (slot_id == GET_SLOT_RESULT_DROP_INCOMING) {
+        return -1;
+    }
+
+    // get_slot said there is no free slot.
+    if (slot_id == GET_SLOT_RESULT_DROP_OLDEST_SLOT) {
+        LOGGER_DEBUG(log, "there was no free slot, so we process the oldest frame");
+        // We now own the frame.
+        struct RTPMessage *m_new = process_frame(log, session->work_buffer_list, 0);
+
+        // The process_frame function returns NULL if there is no slot 0, i.e.
+        // the work buffer list is completely empty. It can't be empty, because
+        // get_slot just told us it's full, so process_frame must return non-null.
+        assert(m_new != nullptr);
+
+        LOGGER_DEBUG(log, "-- handle_video_packet -- CALLBACK-001a b0=%d b1=%d", (int)m_new->data[0], (int)m_new->data[1]);
+        update_bwc_values(log, session, m_new);
+        // Pass ownership of m_new to the callback.
+        session->mcb(session->cs, m_new);
+        // Now we no longer own m_new.
+        m_new = nullptr;
+
+        // Now we must have a free slot, so we either get that slot, i.e. >= 0,
+        // or get told to drop the incoming packet if it's too old.
+        slot_id = get_slot(log, session->work_buffer_list, is_keyframe, header, /* is_multipart */false);
+
+        if (slot_id == GET_SLOT_RESULT_DROP_INCOMING) {
+            // The incoming frame is too old, so we drop it.
+            return -1;
+        }
+    }
+
+    // We must have a valid slot here.
+    assert(slot_id >= 0);
+
+    LOGGER_DEBUG(log, "fill_data_into_slot.1");
+
+    // fill in this part into the slot buffer at the correct offset
+    if (!fill_data_into_slot(
+                log,
+                session->work_buffer_list,
+                slot_id,
+                is_keyframe,
+                header,
+                incoming_data,
+                incoming_data_length)) {
+        // Memory allocation failed. Return error.
+        return -1;
+    }
+
+    struct RTPMessage *m_new = process_frame(log, session->work_buffer_list, slot_id);
+
+    if (m_new) {
+        LOGGER_DEBUG(log, "-- handle_video_packet -- CALLBACK-003a b0=%d b1=%d", (int)m_new->data[0], (int)m_new->data[1]);
+        update_bwc_values(log, session, m_new);
+        session->mcb(session->cs, m_new);
+
+        m_new = nullptr;
+    }
+
+    return 0;
+}
+
+/**
+ * @return -1 on error, 0 on success.
+ */
+static int handle_rtp_packet(Messenger *m, uint32_t friendnumber, const uint8_t *data, uint16_t length, void *object)
+{
+    RTPSession *session = (RTPSession *)object;
+
+    if (!session || length < RTP_HEADER_SIZE + 1) {
+        LOGGER_WARNING(m->log, "No session or invalid length of received buffer!");
+        return -1;
+    }
+
+    // Get the packet type.
+    const uint8_t packet_type = data[0];
+    ++data;
+    --length;
+
+    // Unpack the header.
+    struct RTPHeader header;
+    rtp_header_unpack(data, &header);
+
+    if (header.pt != packet_type % 128) {
+        LOGGER_WARNING(m->log, "RTPHeader packet type and Tox protocol packet type did not agree: %d != %d",
+                       header.pt, packet_type % 128);
+        return -1;
+    }
+
+    if (header.pt != session->payload_type % 128) {
+        LOGGER_WARNING(m->log, "RTPHeader packet type does not match this session's payload type: %d != %d",
+                       header.pt, session->payload_type % 128);
+        return -1;
+    }
+
+    if (header.offset_full >= header.data_length_full) {
+        LOGGER_ERROR(m->log, "Invalid video packet: frame offset (%u) >= full frame length (%u)",
+                     (unsigned)header.offset_full, (unsigned)header.data_length_full);
+        return -1;
+    }
+
+    if (header.offset_lower >= header.data_length_lower) {
+        LOGGER_ERROR(m->log, "Invalid old protocol video packet: frame offset (%u) >= full frame length (%u)",
+                     (unsigned)header.offset_lower, (unsigned)header.data_length_lower);
+        return -1;
+    }
+
+    LOGGER_DEBUG(m->log, "header.pt %d, video %d", (uint8_t)header.pt, (rtp_TypeVideo % 128));
+
+    // The sender uses the new large-frame capable protocol and is sending a
+    // video packet.
+    if ((header.flags & RTP_LARGE_FRAME) && header.pt == (rtp_TypeVideo % 128)) {
+        return handle_video_packet(session, &header, data + RTP_HEADER_SIZE, length - RTP_HEADER_SIZE, m->log);
+    }
+
+    // everything below here is for the old 16 bit protocol ------------------
+
+    if (header.data_length_lower == length - RTP_HEADER_SIZE) {
+        /* The message is sent in single part */
+
+        /* Message is not late; pick up the latest parameters */
+        session->rsequnum = header.sequnum;
+        session->rtimestamp = header.timestamp;
+        bwc_add_recv(session->bwc, length);
+
+        /* Invoke processing of active multiparted message */
+        if (session->mp) {
+            session->mcb(session->cs, session->mp);
+            session->mp = nullptr;
+        }
+
+        /* The message came in the allowed time;
+         */
+
+        return session->mcb(session->cs, new_message(&header, length - RTP_HEADER_SIZE, data + RTP_HEADER_SIZE,
+                            length - RTP_HEADER_SIZE));
+    }
+
+    /* The message is sent in multiple parts */
+
+    if (session->mp) {
+        /* There are 2 possible situations in this case:
+         *      1) being that we got the part of already processing message.
+         *      2) being that we got the part of a new/old message.
+         *
+         * We handle them differently as we only allow a single multiparted
+         * processing message
+         */
+        if (session->mp->header.sequnum == header.sequnum &&
+                session->mp->header.timestamp == header.timestamp) {
+            /* First case */
+
+            /* Make sure we have enough allocated memory */
+            if (session->mp->header.data_length_lower - session->mp->len < length - RTP_HEADER_SIZE ||
+                    session->mp->header.data_length_lower <= header.offset_lower) {
+                /* There happened to be some corruption on the stream;
+                 * continue wihtout this part
+                 */
+                return 0;
+            }
+
+            memcpy(session->mp->data + header.offset_lower, data + RTP_HEADER_SIZE,
+                   length - RTP_HEADER_SIZE);
+            session->mp->len += length - RTP_HEADER_SIZE;
+            bwc_add_recv(session->bwc, length);
+
+            if (session->mp->len == session->mp->header.data_length_lower) {
+                /* Received a full message; now push it for the further
+                 * processing.
+                 */
+                session->mcb(session->cs, session->mp);
+                session->mp = nullptr;
+            }
+        } else {
+            /* Second case */
+            if (session->mp->header.timestamp > header.timestamp) {
+                /* The received message part is from the old message;
+                 * discard it.
+                 */
+                return 0;
+            }
+
+            /* Push the previous message for processing */
+            session->mcb(session->cs, session->mp);
+
+            session->mp = nullptr;
+            goto NEW_MULTIPARTED;
+        }
+    } else {
+        /* In this case threat the message as if it was received in order
+         */
+        /* This is also a point for new multiparted messages */
+NEW_MULTIPARTED:
+
+        /* Message is not late; pick up the latest parameters */
+        session->rsequnum = header.sequnum;
+        session->rtimestamp = header.timestamp;
+        bwc_add_recv(session->bwc, length);
+
+        /* Store message.
+         */
+        session->mp = new_message(&header, header.data_length_lower, data + RTP_HEADER_SIZE, length - RTP_HEADER_SIZE);
+        memmove(session->mp->data + header.offset_lower, session->mp->data, session->mp->len);
+    }
+
+    return 0;
+}
 
 size_t rtp_header_pack(uint8_t *const rdata, const struct RTPHeader *header)
 {
     uint8_t *p = rdata;
-    *p++ = (header->protocol_version & 3) << 6
+    *p++ = (header->ve & 3) << 6
            | (header->pe & 1) << 5
            | (header->xe & 1) << 4
            | (header->cc & 0xf);
@@ -62,11 +608,10 @@ size_t rtp_header_pack(uint8_t *const rdata, const struct RTPHeader *header)
     return p - rdata;
 }
 
-
 size_t rtp_header_unpack(const uint8_t *data, struct RTPHeader *header)
 {
     const uint8_t *p = data;
-    header->protocol_version = (*p >> 6) & 3;
+    header->ve = (*p >> 6) & 3;
     header->pe = (*p >> 5) & 1;
     header->xe = (*p >> 4) & 1;
     header->cc = *p & 0xf;
@@ -93,44 +638,56 @@ size_t rtp_header_unpack(const uint8_t *data, struct RTPHeader *header)
 }
 
 
-int handle_rtp_packet(Messenger *m, uint32_t friendnumber, const uint8_t *data, uint16_t length, void *object);
-
-
 RTPSession *rtp_new(int payload_type, Messenger *m, uint32_t friendnumber,
                     BWController *bwc, void *cs,
                     int (*mcb)(void *, struct RTPMessage *))
 {
-    assert(mcb);
-    assert(cs);
-    assert(m);
+    assert(mcb != nullptr);
+    assert(cs != nullptr);
+    assert(m != nullptr);
 
-    RTPSession *retu = (RTPSession *)calloc(1, sizeof(RTPSession));
+    RTPSession *session = (RTPSession *)calloc(1, sizeof(RTPSession));
 
-    if (!retu) {
+    if (!session) {
         LOGGER_WARNING(m->log, "Alloc failed! Program might misbehave!");
         return nullptr;
     }
 
-    retu->ssrc = random_u32();
-    retu->payload_type = payload_type;
+    session->work_buffer_list = (struct RTPWorkBufferList *)calloc(1, sizeof(struct RTPWorkBufferList));
 
-    retu->m = m;
-    retu->friend_number = friendnumber;
+    if (session->work_buffer_list == nullptr) {
+        LOGGER_ERROR(m->log, "out of memory while allocating work buffer list");
+        free(session);
+        return nullptr;
+    }
 
-    /* Also set payload type as prefix */
+    // First entry is free.
+    session->work_buffer_list->next_free_entry = 0;
+
+    session->ssrc = payload_type == rtp_TypeVideo ? 0 : random_u32();
+    session->payload_type = payload_type;
+    session->m = m;
+    session->friend_number = friendnumber;
 
-    retu->bwc = bwc;
-    retu->cs = cs;
-    retu->mcb = mcb;
+    // set NULL just in case
+    session->mp = nullptr;
+    session->first_packets_counter = 1;
 
-    if (-1 == rtp_allow_receiving(retu)) {
+    /* Also set payload type as prefix */
+    session->bwc = bwc;
+    session->cs = cs;
+    session->mcb = mcb;
+
+    if (-1 == rtp_allow_receiving(session)) {
         LOGGER_WARNING(m->log, "Failed to start rtp receiving mode");
-        free(retu);
+        free(session->work_buffer_list);
+        free(session);
         return nullptr;
     }
 
-    return retu;
+    return session;
 }
+
 void rtp_kill(RTPSession *session)
 {
     if (!session) {
@@ -138,10 +695,15 @@ void rtp_kill(RTPSession *session)
     }
 
     LOGGER_DEBUG(session->m->log, "Terminated RTP session: %p", session);
-
     rtp_stop_receiving(session);
+
+    LOGGER_DEBUG(session->m->log, "Terminated RTP session V3 work_buffer_list->next_free_entry: %d",
+                 (int)session->work_buffer_list->next_free_entry);
+
+    free(session->work_buffer_list);
     free(session);
 }
+
 int rtp_allow_receiving(RTPSession *session)
 {
     if (session == nullptr) {
@@ -157,6 +719,7 @@ int rtp_allow_receiving(RTPSession *session)
     LOGGER_DEBUG(session->m->log, "Started receiving on session: %p", session);
     return 0;
 }
+
 int rtp_stop_receiving(RTPSession *session)
 {
     if (session == nullptr) {
@@ -168,42 +731,76 @@ int rtp_stop_receiving(RTPSession *session)
     LOGGER_DEBUG(session->m->log, "Stopped receiving on session: %p", session);
     return 0;
 }
-int rtp_send_data(RTPSession *session, const uint8_t *data, uint16_t length, Logger *log)
+
+/**
+ * @param input is raw vpx data.
+ * @param length is the length of the raw data.
+ */
+int rtp_send_data(RTPSession *session, const uint8_t *data, uint32_t length,
+                  bool is_keyframe, Logger *log)
 {
     if (!session) {
         LOGGER_ERROR(log, "No session!");
         return -1;
     }
 
-    VLA(uint8_t, rdata, length + RTP_HEADER_SIZE + 1);
-    memset(rdata, 0, SIZEOF_VLA(rdata));
+    uint8_t is_video_payload = 0;
 
-    rdata[0] = session->payload_type;
+    if (session->payload_type == rtp_TypeVideo) {
+        is_video_payload = 1;
+    }
 
     struct RTPHeader header = {0};
 
-    header.protocol_version = 2;
+    header.ve = 2;  // this is unused in toxav
+
     header.pe = 0;
+
     header.xe = 0;
+
     header.cc = 0;
 
     header.ma = 0;
+
     header.pt = session->payload_type % 128;
 
     header.sequnum = session->sequnum;
+
     header.timestamp = current_time_monotonic();
+
     header.ssrc = session->ssrc;
 
     header.offset_lower = 0;
+
+    // here the highest bits gets stripped anyway, no need to do keyframe bit magic here!
     header.data_length_lower = length;
 
-    if (MAX_CRYPTO_DATA_SIZE > length + RTP_HEADER_SIZE + 1) {
+    header.flags = RTP_LARGE_FRAME;
 
+    uint16_t length_safe = (uint16_t)length;
+
+    if (length > UINT16_MAX) {
+        length_safe = UINT16_MAX;
+    }
+
+    header.data_length_lower = length_safe;
+    header.data_length_full = length; // without header
+    header.offset_lower = 0;
+    header.offset_full = 0;
+
+    if (is_keyframe) {
+        header.flags |= RTP_KEY_FRAME;
+    }
+
+    VLA(uint8_t, rdata, length + RTP_HEADER_SIZE + 1);
+    memset(rdata, 0, SIZEOF_VLA(rdata));
+    rdata[0] = session->payload_type;  // packet id == payload_type
+
+    if (MAX_CRYPTO_DATA_SIZE > (length + RTP_HEADER_SIZE + 1)) {
         /**
          * The length is lesser than the maximum allowed length (including header)
          * Send the packet in single piece.
          */
-
         rtp_header_pack(rdata + 1, &header);
         memcpy(rdata + 1 + RTP_HEADER_SIZE, data, length);
 
@@ -211,13 +808,11 @@ int rtp_send_data(RTPSession *session, const uint8_t *data, uint16_t length, Log
             LOGGER_WARNING(session->m->log, "RTP send failed (len: %d)! std error: %s", SIZEOF_VLA(rdata), strerror(errno));
         }
     } else {
-
         /**
          * The length is greater than the maximum allowed length (including header)
          * Send the packet in multiple pieces.
          */
-
-        uint16_t sent = 0;
+        uint32_t sent = 0;
         uint16_t piece = MAX_CRYPTO_DATA_SIZE - (RTP_HEADER_SIZE + 1);
 
         while ((length - sent) + RTP_HEADER_SIZE + 1 > MAX_CRYPTO_DATA_SIZE) {
@@ -232,6 +827,7 @@ int rtp_send_data(RTPSession *session, const uint8_t *data, uint16_t length, Log
 
             sent += piece;
             header.offset_lower = sent;
+            header.offset_full = sent; // raw data offset, without any header
         }
 
         /* Send remaining */
@@ -252,215 +848,3 @@ int rtp_send_data(RTPSession *session, const uint8_t *data, uint16_t length, Log
     session->sequnum ++;
     return 0;
 }
-
-
-static bool chloss(const RTPSession *session, const struct RTPHeader *header)
-{
-    if (header->timestamp < session->rtimestamp) {
-        uint16_t hosq, lost = 0;
-
-        hosq = header->sequnum;
-
-        lost = (hosq > session->rsequnum) ?
-               (session->rsequnum + 65535) - hosq :
-               session->rsequnum - hosq;
-
-        fprintf(stderr, "Lost packet\n");
-
-        while (lost --) {
-            bwc_add_lost(session->bwc, 0);
-        }
-
-        return true;
-    }
-
-    return false;
-}
-static struct RTPMessage *new_message(size_t allocate_len, const uint8_t *data, uint16_t data_length)
-{
-    assert(allocate_len >= data_length);
-
-    struct RTPMessage *msg = (struct RTPMessage *)calloc(sizeof(struct RTPMessage) +
-                             (allocate_len - RTP_HEADER_SIZE), 1);
-
-    if (msg == nullptr) {
-        return nullptr;
-    }
-
-    msg->len = data_length - RTP_HEADER_SIZE;
-    rtp_header_unpack(data, &msg->header);
-    memcpy(msg->data, data + RTP_HEADER_SIZE, allocate_len - RTP_HEADER_SIZE);
-
-    return msg;
-}
-
-int handle_rtp_packet(Messenger *m, uint32_t friendnumber, const uint8_t *data, uint16_t length, void *object)
-{
-    (void) m;
-    (void) friendnumber;
-
-    RTPSession *session = (RTPSession *)object;
-
-    data ++;
-    length--;
-
-    if (!session || length < RTP_HEADER_SIZE) {
-        LOGGER_WARNING(m->log, "No session or invalid length of received buffer!");
-        return -1;
-    }
-
-    struct RTPHeader header;
-
-    rtp_header_unpack(data, &header);
-
-    if (header.pt != session->payload_type % 128) {
-        LOGGER_WARNING(m->log, "Invalid payload type with the session");
-        return -1;
-    }
-
-    if (header.offset_lower >= header.data_length_lower) {
-        /* Never allow this case to happen */
-        return -1;
-    }
-
-    bwc_feed_avg(session->bwc, length);
-
-    if (header.data_length_lower == length - RTP_HEADER_SIZE) {
-        /* The message is sent in single part */
-
-        /* Only allow messages which have arrived in order;
-         * drop late messages
-         */
-        if (chloss(session, &header)) {
-            return 0;
-        }
-
-        /* Message is not late; pick up the latest parameters */
-        session->rsequnum = header.sequnum;
-        session->rtimestamp = header.timestamp;
-
-        bwc_add_recv(session->bwc, length);
-
-        /* Invoke processing of active multiparted message */
-        if (session->mp) {
-            if (session->mcb) {
-                session->mcb(session->cs, session->mp);
-            } else {
-                free(session->mp);
-            }
-
-            session->mp = nullptr;
-        }
-
-        /* The message came in the allowed time;
-         * process it only if handler for the session is present.
-         */
-
-        if (!session->mcb) {
-            return 0;
-        }
-
-        return session->mcb(session->cs, new_message(length, data, length));
-    }
-
-    /* The message is sent in multiple parts */
-
-    if (session->mp) {
-        /* There are 2 possible situations in this case:
-         *      1) being that we got the part of already processing message.
-         *      2) being that we got the part of a new/old message.
-         *
-         * We handle them differently as we only allow a single multiparted
-         * processing message
-         */
-
-        if (session->mp->header.sequnum == header.sequnum &&
-                session->mp->header.timestamp == header.timestamp) {
-            /* First case */
-
-            /* Make sure we have enough allocated memory */
-            if (session->mp->header.data_length_lower - session->mp->len < length - RTP_HEADER_SIZE ||
-                    session->mp->header.data_length_lower <= header.offset_lower) {
-                /* There happened to be some corruption on the stream;
-                 * continue wihtout this part
-                 */
-                return 0;
-            }
-
-            memcpy(session->mp->data + header.offset_lower, data + RTP_HEADER_SIZE,
-                   length - RTP_HEADER_SIZE);
-
-            session->mp->len += length - RTP_HEADER_SIZE;
-
-            bwc_add_recv(session->bwc, length);
-
-            if (session->mp->len == session->mp->header.data_length_lower) {
-                /* Received a full message; now push it for the further
-                 * processing.
-                 */
-                if (session->mcb) {
-                    session->mcb(session->cs, session->mp);
-                } else {
-                    free(session->mp);
-                }
-
-                session->mp = nullptr;
-            }
-        } else {
-            /* Second case */
-
-            if (session->mp->header.timestamp > header.timestamp) {
-                /* The received message part is from the old message;
-                 * discard it.
-                 */
-                return 0;
-            }
-
-            /* Measure missing parts of the old message */
-            bwc_add_lost(session->bwc,
-                         (session->mp->header.data_length_lower - session->mp->len) +
-
-                         /* Must account sizes of rtp headers too */
-                         ((session->mp->header.data_length_lower - session->mp->len) /
-                          MAX_CRYPTO_DATA_SIZE) * RTP_HEADER_SIZE);
-
-            /* Push the previous message for processing */
-            if (session->mcb) {
-                session->mcb(session->cs, session->mp);
-            } else {
-                free(session->mp);
-            }
-
-            session->mp = nullptr;
-            goto NEW_MULTIPARTED;
-        }
-    } else {
-        /* In this case threat the message as if it was received in order
-         */
-
-        /* This is also a point for new multiparted messages */
-NEW_MULTIPARTED:
-
-        /* Only allow messages which have arrived in order;
-         * drop late messages
-         */
-        if (chloss(session, &header)) {
-            return 0;
-        }
-
-        /* Message is not late; pick up the latest parameters */
-        session->rsequnum = header.sequnum;
-        session->rtimestamp = header.timestamp;
-
-        bwc_add_recv(session->bwc, length);
-
-        /* Again, only store message if handler is present
-         */
-        if (session->mcb) {
-            session->mp = new_message(header.data_length_lower + RTP_HEADER_SIZE, data, length);
-            memmove(session->mp->data + header.offset_lower, session->mp->data, session->mp->len);
-        }
-    }
-
-    return 0;
-}
diff --git a/toxav/rtp.h b/toxav/rtp.h
index c8af08d7..a310d58a 100644
--- a/toxav/rtp.h
+++ b/toxav/rtp.h
@@ -66,9 +66,10 @@ enum RTPFlags {
     RTP_KEY_FRAME = 1 << 1,
 };
 
+
 struct RTPHeader {
     /* Standard RTP header */
-    unsigned protocol_version: 2; /* Version has only 2 bits! */
+    unsigned ve: 2; /* Version has only 2 bits! */
     unsigned pe: 1; /* Padding */
     unsigned xe: 1; /* Extra header */
     unsigned cc: 4; /* Contributing sources count */
@@ -113,33 +114,71 @@ struct RTPHeader {
     uint16_t data_length_lower;
 };
 
+
 struct RTPMessage {
+    /**
+     * This is used in the old code that doesn't deal with large frames, i.e.
+     * the audio code or receiving code for old 16 bit messages. We use it to
+     * record the number of bytes received so far in a multi-part message. The
+     * multi-part message in the old code is stored in \ref RTPSession::mp.
+     */
     uint16_t len;
 
     struct RTPHeader header;
     uint8_t data[];
 };
 
+#define USED_RTP_WORKBUFFER_COUNT 3
+
+/**
+ * One slot in the work buffer list. Represents one frame that is currently
+ * being assembled.
+ */
+struct RTPWorkBuffer {
+    /**
+     * Whether this slot contains a key frame. This is true iff
+     * buf->header.flags & RTP_KEY_FRAME.
+     */
+    bool is_keyframe;
+    /**
+     * The number of bytes received so far, regardless of which pieces. I.e. we
+     * could have received the first 1000 bytes and the last 1000 bytes with
+     * 4000 bytes in the middle still to come, and this number would be 2000.
+     */
+    uint32_t received_len;
+    /**
+     * The message currently being assembled.
+     */
+    struct RTPMessage *buf;
+};
+
+struct RTPWorkBufferList {
+    int8_t next_free_entry;
+    struct RTPWorkBuffer work_buffer[USED_RTP_WORKBUFFER_COUNT];
+};
+
+#define DISMISS_FIRST_LOST_VIDEO_PACKET_COUNT 10
+
 /**
  * RTP control session.
  */
-typedef struct {
+typedef struct RTPSession {
     uint8_t  payload_type;
     uint16_t sequnum;      /* Sending sequence number */
     uint16_t rsequnum;     /* Receiving sequence number */
     uint32_t rtimestamp;
-    uint32_t ssrc;
-
+    uint32_t ssrc; //  this seems to be unused!?
     struct RTPMessage *mp; /* Expected parted message */
-
+    struct RTPWorkBufferList *work_buffer_list;
+    uint8_t  first_packets_counter; /* dismiss first few lost video packets */
     Messenger *m;
     uint32_t friend_number;
-
     BWController *bwc;
     void *cs;
     int (*mcb)(void *, struct RTPMessage *msg);
 } RTPSession;
 
+
 /**
  * Serialise an RTPHeader to bytes to be sent over the network.
  *
@@ -164,7 +203,17 @@ RTPSession *rtp_new(int payload_type, Messenger *m, uint32_t friendnumber,
 void rtp_kill(RTPSession *session);
 int rtp_allow_receiving(RTPSession *session);
 int rtp_stop_receiving(RTPSession *session);
-int rtp_send_data(RTPSession *session, const uint8_t *data, uint16_t length, Logger *log);
+/**
+ * Send a frame of audio or video data, chunked in \ref RTPMessage instances.
+ *
+ * @param session The A/V session to send the data for.
+ * @param data A byte array of length \p length.
+ * @param length The number of bytes to send from @p data.
+ * @param is_keyframe Whether this video frame is a key frame. If it is an
+ *   audio frame, this parameter is ignored.
+ */
+int rtp_send_data(RTPSession *session, const uint8_t *data, uint32_t length,
+                  bool is_keyframe, Logger *log);
 
 #ifdef __cplusplus
 }  // extern "C"
diff --git a/toxav/rtp_test.cpp b/toxav/rtp_test.cpp
index 60534b07..d6717a28 100644
--- a/toxav/rtp_test.cpp
+++ b/toxav/rtp_test.cpp
@@ -38,7 +38,7 @@ TEST(Rtp, Deserialisation)
     RTPHeader unpacked = {0};
     EXPECT_EQ(rtp_header_unpack(rdata, &unpacked), RTP_HEADER_SIZE);
 
-    EXPECT_EQ(header.protocol_version, unpacked.protocol_version);
+    EXPECT_EQ(header.ve, unpacked.ve);
     EXPECT_EQ(header.pe, unpacked.pe);
     EXPECT_EQ(header.xe, unpacked.xe);
     EXPECT_EQ(header.cc, unpacked.cc);
diff --git a/toxav/toxav.c b/toxav/toxav.c
index c48fc192..4e45b747 100644
--- a/toxav/toxav.c
+++ b/toxav/toxav.c
@@ -36,7 +36,18 @@
 #include <stdlib.h>
 #include <string.h>
 
-#define MAX_ENCODE_TIME_US ((1000 / 24) * 1000)
+// TODO: don't hardcode this, let the application choose it
+// VPX Info: Time to spend encoding, in microseconds (it's a *soft* deadline)
+#define WANTED_MAX_ENCODER_FPS (40)
+#define MAX_ENCODE_TIME_US (1000000 / WANTED_MAX_ENCODER_FPS) // to allow x fps
+
+#define VIDEO_SEND_X_KEYFRAMES_FIRST 7 // force the first n frames to be keyframes!
+
+/*
+VPX_DL_REALTIME       (1)       deadline parameter analogous to VPx REALTIME mode.
+VPX_DL_GOOD_QUALITY   (1000000) deadline parameter analogous to VPx GOOD QUALITY mode.
+VPX_DL_BEST_QUALITY   (0)       deadline parameter analogous to VPx BEST QUALITY mode.
+*/
 
 typedef struct ToxAVCall_s {
     ToxAV *av;
@@ -752,13 +763,12 @@ bool toxav_audio_send_frame(ToxAV *av, uint32_t friend_number, const int16_t *pc
             goto END;
         }
 
-        if (rtp_send_data(call->audio.first, dest, vrc + sizeof(sampling_rate), av->m->log) != 0) {
+        if (rtp_send_data(call->audio.first, dest, vrc + sizeof(sampling_rate), false, av->m->log) != 0) {
             LOGGER_WARNING(av->m->log, "Failed to send audio packet");
             rc = TOXAV_ERR_SEND_FRAME_RTP_FAILED;
         }
     }
 
-
     pthread_mutex_unlock(call->mutex_audio);
 
 END:
@@ -769,12 +779,15 @@ END:
 
     return rc == TOXAV_ERR_SEND_FRAME_OK;
 }
+
 bool toxav_video_send_frame(ToxAV *av, uint32_t friend_number, uint16_t width, uint16_t height, const uint8_t *y,
                             const uint8_t *u, const uint8_t *v, TOXAV_ERR_SEND_FRAME *error)
 {
     TOXAV_ERR_SEND_FRAME rc = TOXAV_ERR_SEND_FRAME_OK;
     ToxAVCall *call;
 
+    int vpx_encode_flags = 0;
+
     if (m_friend_exists(av->m, friend_number) == 0) {
         rc = TOXAV_ERR_SEND_FRAME_FRIEND_NOT_FOUND;
         goto END;
@@ -810,12 +823,28 @@ bool toxav_video_send_frame(ToxAV *av, uint32_t friend_number, uint16_t width, u
         goto END;
     }
 
-    if (vc_reconfigure_encoder(call->video.second, call->video_bit_rate * 1000, width, height) != 0) {
+    if (vc_reconfigure_encoder(call->video.second, call->video_bit_rate * 1000, width, height, -1) != 0) {
         pthread_mutex_unlock(call->mutex_video);
         rc = TOXAV_ERR_SEND_FRAME_INVALID;
         goto END;
     }
 
+    if (call->video.first->ssrc < VIDEO_SEND_X_KEYFRAMES_FIRST) {
+        // Key frame flag for first frames
+        vpx_encode_flags = VPX_EFLAG_FORCE_KF;
+        LOGGER_INFO(av->m->log, "I_FRAME_FLAG:%d only-i-frame mode", call->video.first->ssrc);
+
+        call->video.first->ssrc++;
+    } else if (call->video.first->ssrc == VIDEO_SEND_X_KEYFRAMES_FIRST) {
+        // normal keyframe placement
+        vpx_encode_flags = 0;
+        LOGGER_INFO(av->m->log, "I_FRAME_FLAG:%d normal mode", call->video.first->ssrc);
+
+        call->video.first->ssrc++;
+    }
+
+    // we start with I-frames (full frames) and then switch to normal mode later
+
     { /* Encode */
         vpx_image_t img;
         img.w = img.h = img.d_w = img.d_h = 0;
@@ -829,7 +858,7 @@ bool toxav_video_send_frame(ToxAV *av, uint32_t friend_number, uint16_t width, u
         memcpy(img.planes[VPX_PLANE_V], v, (width / 2) * (height / 2));
 
         vpx_codec_err_t vrc = vpx_codec_encode(call->video.second->encoder, &img,
-                                               call->video.second->frame_counter, 1, 0, MAX_ENCODE_TIME_US);
+                                               call->video.second->frame_counter, 1, vpx_encode_flags, MAX_ENCODE_TIME_US);
 
         vpx_img_free(&img);
 
@@ -847,22 +876,31 @@ bool toxav_video_send_frame(ToxAV *av, uint32_t friend_number, uint16_t width, u
         vpx_codec_iter_t iter = nullptr;
         const vpx_codec_cx_pkt_t *pkt;
 
-        while ((pkt = vpx_codec_get_cx_data(call->video.second->encoder, &iter))) {
+        while ((pkt = vpx_codec_get_cx_data(call->video.second->encoder, &iter)) != nullptr) {
             if (pkt->kind == VPX_CODEC_CX_FRAME_PKT) {
-                const uint8_t *buf = (const uint8_t *)pkt->data.frame.buf;
-                const uint8_t *end = buf + pkt->data.frame.sz;
-
-                while (buf < end) {
-                    uint16_t size = MIN(UINT16_MAX, end - buf);
-
-                    if (rtp_send_data(call->video.first, buf, size, av->m->log) < 0) {
-                        pthread_mutex_unlock(call->mutex_video);
-                        LOGGER_WARNING(av->m->log, "Could not send video frame: %s\n", strerror(errno));
-                        rc = TOXAV_ERR_SEND_FRAME_RTP_FAILED;
-                        goto END;
-                    }
-
-                    buf += size;
+                const bool is_keyframe = (pkt->data.frame.flags & VPX_FRAME_IS_KEY) != 0;
+
+                // https://www.webmproject.org/docs/webm-sdk/structvpx__codec__cx__pkt.html
+                // pkt->data.frame.sz -> size_t
+                const uint32_t frame_length_in_bytes = pkt->data.frame.sz;
+
+                const int res = rtp_send_data(
+                                    call->video.first,
+                                    (const uint8_t *)pkt->data.frame.buf,
+                                    frame_length_in_bytes,
+                                    is_keyframe,
+                                    av->m->log);
+
+                LOGGER_DEBUG(av->m->log, "+ _sending_FRAME_TYPE_==%s bytes=%d frame_len=%d", is_keyframe ? "K" : ".",
+                             (int)pkt->data.frame.sz, (int)frame_length_in_bytes);
+                LOGGER_DEBUG(av->m->log, "+ _sending_FRAME_ b0=%d b1=%d", ((const uint8_t *)pkt->data.frame.buf)[0],
+                             ((const uint8_t *)pkt->data.frame.buf)[1]);
+
+                if (res < 0) {
+                    pthread_mutex_unlock(call->mutex_video);
+                    LOGGER_WARNING(av->m->log, "Could not send video frame: %s", strerror(errno));
+                    rc = TOXAV_ERR_SEND_FRAME_RTP_FAILED;
+                    goto END;
                 }
             }
         }
@@ -878,6 +916,7 @@ END:
 
     return rc == TOXAV_ERR_SEND_FRAME_OK;
 }
+
 void toxav_callback_audio_receive_frame(ToxAV *av, toxav_audio_receive_frame_cb *callback, void *user_data)
 {
     pthread_mutex_lock(av->mutex);
@@ -885,6 +924,7 @@ void toxav_callback_audio_receive_frame(ToxAV *av, toxav_audio_receive_frame_cb
     av->acb.second = user_data;
     pthread_mutex_unlock(av->mutex);
 }
+
 void toxav_callback_video_receive_frame(ToxAV *av, toxav_video_receive_frame_cb *callback, void *user_data)
 {
     pthread_mutex_lock(av->mutex);
@@ -893,7 +933,6 @@ void toxav_callback_video_receive_frame(ToxAV *av, toxav_video_receive_frame_cb
     pthread_mutex_unlock(av->mutex);
 }
 
-
 /*******************************************************************************
  *
  * :: Internal
@@ -913,7 +952,8 @@ void callback_bwc(BWController *bwc, uint32_t friend_number, float loss, void *u
 
     LOGGER_DEBUG(call->av->m->log, "Reported loss of %f%%", loss * 100);
 
-    if (loss < .01f) {
+    /* if less than 10% data loss we do nothing! */
+    if (loss < 0.1f) {
         return;
     }
 
@@ -1079,6 +1119,7 @@ bool invoke_call_state_callback(ToxAV *av, uint32_t friend_number, uint32_t stat
 
     return true;
 }
+
 ToxAVCall *call_new(ToxAV *av, uint32_t friend_number, TOXAV_ERR_CALL *error)
 {
     /* Assumes mutex locked */
@@ -1100,7 +1141,6 @@ ToxAVCall *call_new(ToxAV *av, uint32_t friend_number, TOXAV_ERR_CALL *error)
         goto END;
     }
 
-
     call = (ToxAVCall *)calloc(sizeof(ToxAVCall), 1);
 
     if (call == nullptr) {
@@ -1161,6 +1201,7 @@ END:
 
     return call;
 }
+
 ToxAVCall *call_get(ToxAV *av, uint32_t friend_number)
 {
     /* Assumes mutex locked */
@@ -1170,6 +1211,7 @@ ToxAVCall *call_get(ToxAV *av, uint32_t friend_number)
 
     return av->calls[friend_number];
 }
+
 ToxAVCall *call_remove(ToxAVCall *call)
 {
     if (call == nullptr) {
@@ -1217,6 +1259,7 @@ CLEAR:
 
     return nullptr;
 }
+
 bool call_prepare_transmission(ToxAVCall *call)
 {
     /* Assumes mutex locked */
@@ -1305,6 +1348,7 @@ FAILURE_3:
     pthread_mutex_destroy(call->mutex_audio);
     return false;
 }
+
 void call_kill_transmission(ToxAVCall *call)
 {
     if (call == nullptr || call->active == 0) {
diff --git a/toxav/video.c b/toxav/video.c
index eee542a2..0014dbb6 100644
--- a/toxav/video.c
+++ b/toxav/video.c
@@ -33,8 +33,124 @@
 #include <assert.h>
 #include <stdlib.h>
 
-#define MAX_DECODE_TIME_US 0 /* Good quality encode. */
-#define VIDEO_DECODE_BUFFER_SIZE 20
+/**
+ * Soft deadline the decoder should attempt to meet, in "us" (microseconds).
+ * Set to zero for unlimited.
+ *
+ * By convention, the value 1 is used to mean "return as fast as possible."
+ */
+// TODO: don't hardcode this, let the application choose it
+#define WANTED_MAX_DECODER_FPS 40
+
+/**
+ * VPX_DL_REALTIME       (1)
+ * deadline parameter analogous to VPx REALTIME mode.
+ *
+ * VPX_DL_GOOD_QUALITY   (1000000)
+ * deadline parameter analogous to VPx GOOD QUALITY mode.
+ *
+ * VPX_DL_BEST_QUALITY   (0)
+ * deadline parameter analogous to VPx BEST QUALITY mode.
+ */
+#define MAX_DECODE_TIME_US (1000000 / WANTED_MAX_DECODER_FPS) // to allow x fps
+
+/**
+ * Codec control function to set encoder internal speed settings. Changes in
+ * this value influences, among others, the encoder's selection of motion
+ * estimation methods. Values greater than 0 will increase encoder speed at the
+ * expense of quality.
+ *
+ * Note Valid range for VP8: -16..16
+ */
+#define VP8E_SET_CPUUSED_VALUE 16
+
+/**
+ * Initialize encoder with this value. Target bandwidth to use for this stream, in kilobits per second.
+ */
+#define VIDEO_BITRATE_INITIAL_VALUE 5000
+#define VIDEO_DECODE_BUFFER_SIZE 5 // this buffer has normally max. 1 entry
+
+#define VIDEO_CODEC_DECODER_INTERFACE (vpx_codec_vp8_dx())
+#define VIDEO_CODEC_ENCODER_INTERFACE (vpx_codec_vp8_cx())
+
+#define VIDEO_CODEC_DECODER_MAX_WIDTH  800 // its a dummy value, because the struct needs a value there
+#define VIDEO_CODEC_DECODER_MAX_HEIGHT 600 // its a dummy value, because the struct needs a value there
+
+#define VPX_MAX_DIST_NORMAL 40
+#define VPX_MAX_DIST_START 40
+
+#define VPX_MAX_ENCODER_THREADS 4
+#define VPX_MAX_DECODER_THREADS 4
+#define VIDEO__VP8_DECODER_POST_PROCESSING_ENABLED 0
+
+void vc_init_encoder_cfg(Logger *log, vpx_codec_enc_cfg_t *cfg, int16_t kf_max_dist)
+{
+    vpx_codec_err_t rc = vpx_codec_enc_config_default(VIDEO_CODEC_ENCODER_INTERFACE, cfg, 0);
+
+    if (rc != VPX_CODEC_OK) {
+        LOGGER_ERROR(log, "vc_init_encoder_cfg:Failed to get config: %s", vpx_codec_err_to_string(rc));
+    }
+
+    /* Target bandwidth to use for this stream, in kilobits per second */
+    cfg->rc_target_bitrate = VIDEO_BITRATE_INITIAL_VALUE;
+    cfg->g_w = VIDEO_CODEC_DECODER_MAX_WIDTH;
+    cfg->g_h = VIDEO_CODEC_DECODER_MAX_HEIGHT;
+    cfg->g_pass = VPX_RC_ONE_PASS;
+    cfg->g_error_resilient = VPX_ERROR_RESILIENT_DEFAULT | VPX_ERROR_RESILIENT_PARTITIONS;
+    cfg->g_lag_in_frames = 0;
+
+    /* Allow lagged encoding
+     *
+     * If set, this value allows the encoder to consume a number of input
+     * frames before producing output frames. This allows the encoder to
+     * base decisions for the current frame on future frames. This does
+     * increase the latency of the encoding pipeline, so it is not appropriate
+     * in all situations (ex: realtime encoding).
+     *
+     * Note that this is a maximum value -- the encoder may produce frames
+     * sooner than the given limit. Set this value to 0 to disable this
+     * feature.
+     */
+    cfg->kf_min_dist = 0;
+    cfg->kf_mode = VPX_KF_AUTO; // Encoder determines optimal placement automatically
+    cfg->rc_end_usage = VPX_VBR; // what quality mode?
+
+    /*
+     * VPX_VBR    Variable Bit Rate (VBR) mode
+     * VPX_CBR    Constant Bit Rate (CBR) mode
+     * VPX_CQ     Constrained Quality (CQ) mode -> give codec a hint that we may be on low bandwidth connection
+     * VPX_Q    Constant Quality (Q) mode
+     */
+    if (kf_max_dist > 1) {
+        cfg->kf_max_dist = kf_max_dist; // a full frame every x frames minimum (can be more often, codec decides automatically)
+        LOGGER_DEBUG(log, "kf_max_dist=%d (1)", cfg->kf_max_dist);
+    } else {
+        cfg->kf_max_dist = VPX_MAX_DIST_START;
+        LOGGER_DEBUG(log, "kf_max_dist=%d (2)", cfg->kf_max_dist);
+    }
+
+    cfg->g_threads = VPX_MAX_ENCODER_THREADS; // Maximum number of threads to use
+    /* TODO: set these to something reasonable */
+    // cfg->g_timebase.num = 1;
+    // cfg->g_timebase.den = 60; // 60 fps
+    cfg->rc_resize_allowed = 1; // allow encoder to resize to smaller resolution
+    cfg->rc_resize_up_thresh = 40;
+    cfg->rc_resize_down_thresh = 5;
+
+    /* TODO: make quality setting an API call, but start with normal quality */
+#if 0
+    /* Highest-resolution encoder settings */
+    cfg->rc_dropframe_thresh = 0;
+    cfg->rc_resize_allowed = 0;
+    cfg->rc_min_quantizer = 2;
+    cfg->rc_max_quantizer = 56;
+    cfg->rc_undershoot_pct = 100;
+    cfg->rc_overshoot_pct = 15;
+    cfg->rc_buf_initial_sz = 500;
+    cfg->rc_buf_optimal_sz = 600;
+    cfg->rc_buf_sz = 1000;
+#endif
+}
 
 VCSession *vc_new(Logger *log, ToxAV *av, uint32_t friend_number, toxav_video_receive_frame_cb *cb, void *cb_data)
 {
@@ -52,49 +168,72 @@ VCSession *vc_new(Logger *log, ToxAV *av, uint32_t friend_number, toxav_video_re
         return nullptr;
     }
 
+    int cpu_used_value = VP8E_SET_CPUUSED_VALUE;
+
     if (!(vc->vbuf_raw = rb_new(VIDEO_DECODE_BUFFER_SIZE))) {
         goto BASE_CLEANUP;
     }
 
-    rc = vpx_codec_dec_init(vc->decoder, VIDEO_CODEC_DECODER_INTERFACE, nullptr, 0);
+    /*
+     * VPX_CODEC_USE_FRAME_THREADING
+     *    Enable frame-based multi-threading
+     *
+     * VPX_CODEC_USE_ERROR_CONCEALMENT
+     *    Conceal errors in decoded frames
+     */
+    vpx_codec_dec_cfg_t  dec_cfg;
+    dec_cfg.threads = VPX_MAX_DECODER_THREADS; // Maximum number of threads to use
+    dec_cfg.w = VIDEO_CODEC_DECODER_MAX_WIDTH;
+    dec_cfg.h = VIDEO_CODEC_DECODER_MAX_HEIGHT;
+
+    LOGGER_DEBUG(log, "Using VP8 codec for decoder (0)");
+    rc = vpx_codec_dec_init(vc->decoder, VIDEO_CODEC_DECODER_INTERFACE, &dec_cfg,
+                            VPX_CODEC_USE_FRAME_THREADING | VPX_CODEC_USE_POSTPROC);
+
+    if (rc == VPX_CODEC_INCAPABLE) {
+        LOGGER_WARNING(log, "Postproc not supported by this decoder (0)");
+        rc = vpx_codec_dec_init(vc->decoder, VIDEO_CODEC_DECODER_INTERFACE, &dec_cfg, VPX_CODEC_USE_FRAME_THREADING);
+    }
 
     if (rc != VPX_CODEC_OK) {
         LOGGER_ERROR(log, "Init video_decoder failed: %s", vpx_codec_err_to_string(rc));
         goto BASE_CLEANUP;
     }
 
-    /* Set encoder to some initial values
-     */
-    vpx_codec_enc_cfg_t  cfg;
-    rc = vpx_codec_enc_config_default(VIDEO_CODEC_ENCODER_INTERFACE, &cfg, 0);
+    if (VIDEO__VP8_DECODER_POST_PROCESSING_ENABLED == 1) {
+        vp8_postproc_cfg_t pp = {VP8_DEBLOCK, 1, 0};
+        vpx_codec_err_t cc_res = vpx_codec_control(vc->decoder, VP8_SET_POSTPROC, &pp);
 
-    if (rc != VPX_CODEC_OK) {
-        LOGGER_ERROR(log, "Failed to get config: %s", vpx_codec_err_to_string(rc));
-        goto BASE_CLEANUP_1;
+        if (cc_res != VPX_CODEC_OK) {
+            LOGGER_WARNING(log, "Failed to turn on postproc");
+        } else {
+            LOGGER_DEBUG(log, "turn on postproc: OK");
+        }
+    } else {
+        vp8_postproc_cfg_t pp = {0, 0, 0};
+        vpx_codec_err_t cc_res = vpx_codec_control(vc->decoder, VP8_SET_POSTPROC, &pp);
+
+        if (cc_res != VPX_CODEC_OK) {
+            LOGGER_WARNING(log, "Failed to turn OFF postproc");
+        } else {
+            LOGGER_DEBUG(log, "Disable postproc: OK");
+        }
     }
 
-    cfg.rc_target_bitrate = 500000;
-    cfg.g_w = 800;
-    cfg.g_h = 600;
-    cfg.g_pass = VPX_RC_ONE_PASS;
-    /* TODO(mannol): If we set error resilience the app will crash due to bug in vp8.
-       Perhaps vp9 has solved it?*/
-#if 0
-    cfg.g_error_resilient = VPX_ERROR_RESILIENT_DEFAULT | VPX_ERROR_RESILIENT_PARTITIONS;
-#endif
-    cfg.g_lag_in_frames = 0;
-    cfg.kf_min_dist = 0;
-    cfg.kf_max_dist = 48;
-    cfg.kf_mode = VPX_KF_AUTO;
+    /* Set encoder to some initial values
+     */
+    vpx_codec_enc_cfg_t  cfg;
+    vc_init_encoder_cfg(log, &cfg, 1);
 
-    rc = vpx_codec_enc_init(vc->encoder, VIDEO_CODEC_ENCODER_INTERFACE, &cfg, 0);
+    LOGGER_DEBUG(log, "Using VP8 codec for encoder (0.1)");
+    rc = vpx_codec_enc_init(vc->encoder, VIDEO_CODEC_ENCODER_INTERFACE, &cfg, VPX_CODEC_USE_FRAME_THREADING);
 
     if (rc != VPX_CODEC_OK) {
         LOGGER_ERROR(log, "Failed to initialize encoder: %s", vpx_codec_err_to_string(rc));
         goto BASE_CLEANUP_1;
     }
 
-    rc = vpx_codec_control(vc->encoder, VP8E_SET_CPUUSED, 8);
+    rc = vpx_codec_control(vc->encoder, VP8E_SET_CPUUSED, cpu_used_value);
 
     if (rc != VPX_CODEC_OK) {
         LOGGER_ERROR(log, "Failed to set encoder control setting: %s", vpx_codec_err_to_string(rc));
@@ -102,6 +241,20 @@ VCSession *vc_new(Logger *log, ToxAV *av, uint32_t friend_number, toxav_video_re
         goto BASE_CLEANUP_1;
     }
 
+    /*
+    VPX_CTRL_USE_TYPE(VP8E_SET_NOISE_SENSITIVITY,  unsigned int)
+    control function to set noise sensitivity
+      0: off, 1: OnYOnly, 2: OnYUV, 3: OnYUVAggressive, 4: Adaptive
+    */
+    /*
+      rc = vpx_codec_control(vc->encoder, VP8E_SET_NOISE_SENSITIVITY, 2);
+
+      if (rc != VPX_CODEC_OK) {
+          LOGGER_ERROR(log, "Failed to set encoder control setting: %s", vpx_codec_err_to_string(rc));
+          vpx_codec_destroy(vc->encoder);
+          goto BASE_CLEANUP_1;
+      }
+     */
     vc->linfts = current_time_monotonic();
     vc->lcfd = 60;
     vc->vcb.first = cb;
@@ -109,9 +262,7 @@ VCSession *vc_new(Logger *log, ToxAV *av, uint32_t friend_number, toxav_video_re
     vc->friend_number = friend_number;
     vc->av = av;
     vc->log = log;
-
     return vc;
-
 BASE_CLEANUP_1:
     vpx_codec_destroy(vc->decoder);
 BASE_CLEANUP:
@@ -120,6 +271,7 @@ BASE_CLEANUP:
     free(vc);
     return nullptr;
 }
+
 void vc_kill(VCSession *vc)
 {
     if (!vc) {
@@ -128,7 +280,6 @@ void vc_kill(VCSession *vc)
 
     vpx_codec_destroy(vc->encoder);
     vpx_codec_destroy(vc->decoder);
-
     void *p;
 
     while (rb_read((RingBuffer *)vc->vbuf_raw, &p)) {
@@ -136,12 +287,11 @@ void vc_kill(VCSession *vc)
     }
 
     rb_kill((RingBuffer *)vc->vbuf_raw);
-
     pthread_mutex_destroy(vc->queue_mutex);
-
     LOGGER_DEBUG(vc->log, "Terminated video handler: %p", vc);
     free(vc);
 }
+
 void vc_iterate(VCSession *vc)
 {
     if (!vc) {
@@ -154,45 +304,63 @@ void vc_iterate(VCSession *vc)
 
     pthread_mutex_lock(vc->queue_mutex);
 
+    uint32_t full_data_len;
+
     if (rb_read((RingBuffer *)vc->vbuf_raw, (void **)&p)) {
         pthread_mutex_unlock(vc->queue_mutex);
+        const struct RTPHeader *const header = &p->header;
+
+        if (header->flags & RTP_LARGE_FRAME) {
+            full_data_len = header->data_length_full;
+            LOGGER_DEBUG(vc->log, "vc_iterate:001:full_data_len=%d", (int)full_data_len);
+        } else {
+            full_data_len = p->len;
+            LOGGER_DEBUG(vc->log, "vc_iterate:002");
+        }
 
-        rc = vpx_codec_decode(vc->decoder, p->data, p->len, nullptr, MAX_DECODE_TIME_US);
+        LOGGER_DEBUG(vc->log, "vc_iterate: rb_read p->len=%d p->header.xe=%d", (int)full_data_len, p->header.xe);
+        LOGGER_DEBUG(vc->log, "vc_iterate: rb_read rb size=%d", (int)rb_size((RingBuffer *)vc->vbuf_raw));
+        rc = vpx_codec_decode(vc->decoder, p->data, full_data_len, nullptr, MAX_DECODE_TIME_US);
         free(p);
 
         if (rc != VPX_CODEC_OK) {
-            LOGGER_ERROR(vc->log, "Error decoding video: %s", vpx_codec_err_to_string(rc));
+            LOGGER_ERROR(vc->log, "Error decoding video: %d %s", (int)rc, vpx_codec_err_to_string(rc));
         } else {
+            /* Play decoded images */
             vpx_codec_iter_t iter = nullptr;
-            vpx_image_t *dest = vpx_codec_get_frame(vc->decoder, &iter);
+            vpx_image_t *dest = nullptr;
 
-            /* Play decoded images */
-            for (; dest; dest = vpx_codec_get_frame(vc->decoder, &iter)) {
+            while ((dest = vpx_codec_get_frame(vc->decoder, &iter)) != nullptr) {
                 if (vc->vcb.first) {
                     vc->vcb.first(vc->av, vc->friend_number, dest->d_w, dest->d_h,
                                   (const uint8_t *)dest->planes[0], (const uint8_t *)dest->planes[1], (const uint8_t *)dest->planes[2],
                                   dest->stride[0], dest->stride[1], dest->stride[2], vc->vcb.second);
                 }
 
-                vpx_img_free(dest);
+                vpx_img_free(dest); // is this needed? none of the VPx examples show that
             }
         }
 
         return;
+    } else {
+        LOGGER_TRACE(vc->log, "no Video frame data available");
     }
 
     pthread_mutex_unlock(vc->queue_mutex);
 }
+
 int vc_queue_message(void *vcp, struct RTPMessage *msg)
 {
-    /* This function does the reconstruction of video packets.
-     * See more info about video splitting in docs
+    /* This function is called with complete messages
+     * they have already been assembled.
+     * this function gets called from handle_rtp_packet() and handle_rtp_packet_v3()
      */
     if (!vcp || !msg) {
         return -1;
     }
 
     VCSession *vc = (VCSession *)vcp;
+    const struct RTPHeader *const header = &msg->header;
 
     if (msg->header.pt == (rtp_TypeVideo + 2) % 128) {
         LOGGER_WARNING(vc->log, "Got dummy!");
@@ -201,41 +369,45 @@ int vc_queue_message(void *vcp, struct RTPMessage *msg)
     }
 
     if (msg->header.pt != rtp_TypeVideo % 128) {
-        LOGGER_WARNING(vc->log, "Invalid payload type!");
+        LOGGER_WARNING(vc->log, "Invalid payload type! pt=%d", (int)msg->header.pt);
         free(msg);
         return -1;
     }
 
     pthread_mutex_lock(vc->queue_mutex);
-    free(rb_write((RingBuffer *)vc->vbuf_raw, msg));
-    {
-        /* Calculate time took for peer to send us this frame */
-        uint32_t t_lcfd = current_time_monotonic() - vc->linfts;
-        vc->lcfd = t_lcfd > 100 ? vc->lcfd : t_lcfd;
-        vc->linfts = current_time_monotonic();
+
+    if ((header->flags & RTP_LARGE_FRAME) && header->pt == rtp_TypeVideo % 128) {
+        LOGGER_DEBUG(vc->log, "rb_write msg->len=%d b0=%d b1=%d", (int)msg->len, (int)msg->data[0], (int)msg->data[1]);
     }
-    pthread_mutex_unlock(vc->queue_mutex);
 
+    free(rb_write((RingBuffer *)vc->vbuf_raw, msg));
+
+    /* Calculate time it took for peer to send us this frame */
+    uint32_t t_lcfd = current_time_monotonic() - vc->linfts;
+    vc->lcfd = t_lcfd > 100 ? vc->lcfd : t_lcfd;
+    vc->linfts = current_time_monotonic();
+    pthread_mutex_unlock(vc->queue_mutex);
     return 0;
 }
-int vc_reconfigure_encoder(VCSession *vc, uint32_t bit_rate, uint16_t width, uint16_t height)
+
+int vc_reconfigure_encoder(VCSession *vc, uint32_t bit_rate, uint16_t width, uint16_t height, int16_t kf_max_dist)
 {
     if (!vc) {
         return -1;
     }
 
-    vpx_codec_enc_cfg_t cfg = *vc->encoder->config.enc;
+    vpx_codec_enc_cfg_t cfg2 = *vc->encoder->config.enc;
     vpx_codec_err_t rc;
 
-    if (cfg.rc_target_bitrate == bit_rate && cfg.g_w == width && cfg.g_h == height) {
+    if (cfg2.rc_target_bitrate == bit_rate && cfg2.g_w == width && cfg2.g_h == height && kf_max_dist == -1) {
         return 0; /* Nothing changed */
     }
 
-    if (cfg.g_w == width && cfg.g_h == height) {
+    if (cfg2.g_w == width && cfg2.g_h == height && kf_max_dist == -1) {
         /* Only bit rate changed */
-        cfg.rc_target_bitrate = bit_rate;
-
-        rc = vpx_codec_enc_config_set(vc->encoder, &cfg);
+        LOGGER_INFO(vc->log, "bitrate change from: %u to: %u", (uint32_t)cfg2.rc_target_bitrate, (uint32_t)bit_rate);
+        cfg2.rc_target_bitrate = bit_rate;
+        rc = vpx_codec_enc_config_set(vc->encoder, &cfg2);
 
         if (rc != VPX_CODEC_OK) {
             LOGGER_ERROR(vc->log, "Failed to set encoder control setting: %s", vpx_codec_err_to_string(rc));
@@ -245,23 +417,25 @@ int vc_reconfigure_encoder(VCSession *vc, uint32_t bit_rate, uint16_t width, uin
         /* Resolution is changed, must reinitialize encoder since libvpx v1.4 doesn't support
          * reconfiguring encoder to use resolutions greater than initially set.
          */
-
         LOGGER_DEBUG(vc->log, "Have to reinitialize vpx encoder on session %p", vc);
-
+        vpx_codec_ctx_t new_c;
+        vpx_codec_enc_cfg_t  cfg;
+        vc_init_encoder_cfg(vc->log, &cfg, kf_max_dist);
         cfg.rc_target_bitrate = bit_rate;
         cfg.g_w = width;
         cfg.g_h = height;
 
-        vpx_codec_ctx_t new_c;
-
-        rc = vpx_codec_enc_init(&new_c, VIDEO_CODEC_ENCODER_INTERFACE, &cfg, 0);
+        LOGGER_DEBUG(vc->log, "Using VP8 codec for encoder");
+        rc = vpx_codec_enc_init(&new_c, VIDEO_CODEC_ENCODER_INTERFACE, &cfg, VPX_CODEC_USE_FRAME_THREADING);
 
         if (rc != VPX_CODEC_OK) {
             LOGGER_ERROR(vc->log, "Failed to initialize encoder: %s", vpx_codec_err_to_string(rc));
             return -1;
         }
 
-        rc = vpx_codec_control(&new_c, VP8E_SET_CPUUSED, 8);
+        int cpu_used_value = VP8E_SET_CPUUSED_VALUE;
+
+        rc = vpx_codec_control(&new_c, VP8E_SET_CPUUSED, cpu_used_value);
 
         if (rc != VPX_CODEC_OK) {
             LOGGER_ERROR(vc->log, "Failed to set encoder control setting: %s", vpx_codec_err_to_string(rc));
diff --git a/toxav/video.h b/toxav/video.h
index 02670e0a..85ad3129 100644
--- a/toxav/video.h
+++ b/toxav/video.h
@@ -31,8 +31,7 @@
 
 #include <vpx/vp8cx.h>
 #include <vpx/vp8dx.h>
-#define VIDEO_CODEC_DECODER_INTERFACE (vpx_codec_vp8_dx())
-#define VIDEO_CODEC_ENCODER_INTERFACE (vpx_codec_vp8_cx())
+
 
 #include <pthread.h>
 
@@ -64,6 +63,6 @@ VCSession *vc_new(Logger *log, ToxAV *av, uint32_t friend_number, toxav_video_re
 void vc_kill(VCSession *vc);
 void vc_iterate(VCSession *vc);
 int vc_queue_message(void *vcp, struct RTPMessage *msg);
-int vc_reconfigure_encoder(VCSession *vc, uint32_t bit_rate, uint16_t width, uint16_t height);
+int vc_reconfigure_encoder(VCSession *vc, uint32_t bit_rate, uint16_t width, uint16_t height, int16_t kf_max_dist);
 
 #endif /* VIDEO_H */
diff --git a/toxcore/BUILD.bazel b/toxcore/BUILD.bazel
index 934ff16c..d6c3693e 100644
--- a/toxcore/BUILD.bazel
+++ b/toxcore/BUILD.bazel
@@ -33,7 +33,7 @@ cc_test(
     srcs = ["crypto_core_test.cpp"],
     deps = [
         ":crypto_core",
-        "@gtest",
+        "@com_google_googletest//:gtest_main",
     ],
 )
 
@@ -77,7 +77,7 @@ cc_test(
     srcs = ["util_test.cpp"],
     deps = [
         ":network",
-        "@gtest",
+        "@com_google_googletest//:gtest_main",
     ],
 )