Advertise desktop decoder capabilities independently of encoders

tools/chatgui/src/call_video_decoder.cpp

@@ -24,6 +24,29 @@ void CallVideoDecoder::close() {
 #endif
     m->format = {};
 }
+call_video_caps CallVideoDecoder::capabilities() {
+    call_video_caps caps{};
+    for (unsigned codec = 1; codec <= 2; ++codec) {
+        unsigned profiles = 0;
+        for (unsigned profile = 1; profile <= (codec == 1 ? 2u : 1u); ++profile) {
+            uint8_t bytes[8192]; int size = call_video_probe_key(codec, profile, bytes, sizeof(bytes));
+            if (size < 0) continue;
+            call_video_frame f{}; f.call_id = 1; f.flags = CALL_VIDEO_KEY; f.data = bytes; f.size = f.length = size;
+            f.format = {1, 1280, 720, 30, 0, (uint8_t)codec, (uint8_t)(codec == 1 ? 31 : 93), 4000000, (uint8_t)profile};
+            CallVideoDecoder decoder; bool valid = true;
+            for (unsigned i = 0; i < 4 && valid; ++i) {
+                f.frame_id = i + 1; f.pts_us = 1000000 + i * 33333;
+                QImage image; valid = decoder.decode(f, image);
+            }
+            if (valid) profiles |= profile;
+            else DEBUG_WARN(DEBUG_CATEGORY_CALL, "video independent decoder probe failed codec=%u profile=%u", codec, profile);
+        }
+        if (profiles) caps.decode[codec - 1] = {1280, 720, 30, 1280 * 720 * 30, 4000000,
+            (uint8_t)profiles, (uint8_t)(codec == 1 ? 31 : 93)};
+        DEBUG_INFO(DEBUG_CATEGORY_CALL, "video decoder probe codec=%u profiles=%u", codec, profiles);
+    }
+    return caps;
+}
 bool CallVideoDecoder::decode(const call_video_frame& f, QImage& image) {
 #ifdef HAVE_FFMPEG
     auto failed = [this, &f](const char* reason) {