Fallback desktop video on decoder rejection and verify receive-only codecs

tools/chatgui/src/call_video_engine.cpp

@@ -146,6 +146,8 @@ void CallVideoEngine::transmit() {
     CallVideoEncoder encoder;
     call_video_format format{};
     uint64_t appliedRevision = 0, keySerial = 0, request = 0, frameId = 0;
+    uint64_t userRevision = 0, rejectedGeneration = 0;
+    unsigned excluded = 0;
     int64_t lastPts = -1, lastKey = -1;
     bool forceKey = true;
     while (m->running) {
@@ -161,11 +163,28 @@ void CallVideoEngine::transmit() {
           raw = m->raw;
 #endif
         }
+        if (revision != userRevision) { userRevision = revision; excluded = 0; }
+        if (format.generation && state.decoded_generation == format.generation && !state.decoded_accepted
+            && rejectedGeneration != format.generation) {
+            rejectedGeneration = format.generation; excluded |= 1u << format.codec;
+            if (!codec) { appliedRevision = 0; lastKey = -1; m->report(tr("Receiver rejected video; selecting fallback")); }
+            else {
+                m->report(tr("Receiver cannot decode selected codec"));
+                std::lock_guard<std::mutex> guard(m->lock); m->enabled = false; continue;
+            }
+        }
+        if (format.generation && state.have_peer && !call_video_format_supported(&caps, &state.peer, &format)) appliedRevision = 0;
         if (!enabled || !state.have_peer || pts <= lastPts || (lastPts >= 0 && pts - lastPts < 33333)) { idle(); continue; }
         if (revision != appliedRevision) {
             if (lastKey >= 0 && pts - lastKey < 1000000) { idle(); continue; }
             call_video_format next{format.generation + 1, (uint16_t)width, (uint16_t)height, 30, 0, (uint8_t)codec, 0, 4000000, 0};
-            if (call_video_choose(&caps, &state.peer, &next) <= 0 || !encoder.open(next, 1000000)) {
+            bool opened = false;
+            for (int candidate = 2; candidate >= 1; --candidate) {
+                if ((codec && codec != candidate) || (excluded & (1u << candidate))) continue;
+                next.codec = candidate; next.level = next.profile = 0;
+                if (call_video_choose(&caps, &state.peer, &next) > 0 && encoder.open(next, 1000000)) { opened = true; break; }
+            }
+            if (!opened) {
                 m->report(tr("Selected video mode is unavailable to the peer"));
                 std::lock_guard<std::mutex> guard(m->lock); if (m->revision == revision) m->enabled = false;
                 continue;
@@ -209,6 +228,7 @@ void CallVideoEngine::receive() {
     std::deque<Picture> pictures;
     CallVideoDecoder decoder;
     uint64_t sourceEpoch = 0; int64_t lastShown = -1, report = 0; unsigned shown = 0;
+    uint64_t reportedGeneration = 0, rejectedGeneration = 0;
     while (m->running) {
         int64_t now = nowUs(); call_clock_snapshot clock{};
         call_audio_get_clock(m->id, now, &clock);
@@ -228,9 +248,16 @@ void CallVideoEngine::receive() {
         if (pictures.size() < 16) {
             call_video_frame packet{};
             if (call_video_port_pull(m->id, &packet) == 1) {
+                if (packet.format.generation == rejectedGeneration) { u_free((void*)packet.data); continue; }
                 QImage image;
-                if (decoder.decode(packet, image)) pictures.push_back({packet.pts_us, image});
-                else call_video_port_request_key(m->id);
+                if (decoder.decode(packet, image)) {
+                    pictures.push_back({packet.pts_us, image});
+                    if (reportedGeneration != packet.format.generation) {
+                        reportedGeneration = packet.format.generation; call_video_port_decoded(m->id, reportedGeneration, 1);
+                    }
+                } else {
+                    rejectedGeneration = packet.format.generation; call_video_port_decoded(m->id, rejectedGeneration, 0);
+                }
                 u_free((void*)packet.data); continue;
             }
         }

tools/chatgui/tests/test_call_video_encoder.cpp

@@ -45,6 +45,11 @@ private slots:
     void switchesAtScheduledIdr_data() {
         QTest::addColumn<int>("codec"); QTest::newRow("H264") << 1; QTest::newRow("H265") << 2;
     }
+    void independentDecoders() {
+        auto caps = CallVideoDecoder::capabilities();
+        QCOMPARE(caps.decode[0].profiles, uint8_t(3)); QCOMPARE(caps.decode[1].profiles, uint8_t(1));
+        QCOMPARE(caps.encode[0].width, uint16_t(0)); QCOMPARE(caps.encode[1].width, uint16_t(0));
+    }
     void switchesAtScheduledIdr() {
         QFETCH(int, codec);
         auto config = configuration(codec);