Keep desktop video in a resizable window and retain decoder on audio clock updates

tools/chatgui/src/call_video_engine.cpp

@@ -258,8 +258,8 @@ void CallVideoEngine::receive() {
         call_audio_get_clock(m->id, now, &clock);
         if (clock.valid) {
             if (sourceEpoch && sourceEpoch != clock.source_epoch) {
-                pictures.clear(); decoder.close(); call_video_port_request_key(m->id); lastShown = -1;
-                DEBUG_INFO(DEBUG_CATEGORY_CALL, "video playback audio source epoch changed");
+                DEBUG_DEBUG(DEBUG_CATEGORY_CALL, "video audio clock epoch %llu -> %llu; decoder retained",
+                    (unsigned long long)sourceEpoch, (unsigned long long)clock.source_epoch);
             }
             sourceEpoch = clock.source_epoch;
             QImage selected;