Fixup: Fix building with system ffmpeg

System FFmpeg contains multiple codecs for mp3 and
uses whatever it finds first. Chromium only supports one,
and not aware of others.

Force the supported codec for mp3 decoding.

Fixes: QTBUG-130273
Change-Id: Ic25ae719ee0490426ddac8df7544dff04fc0b255
Reviewed-on: https://codereview.qt-project.org/c/qt/qtwebengine-chromium/+/599610
Reviewed-by: Allan Sandfeld Jensen <[email protected]>
(cherry picked from commit 3b9f0ed)
Reviewed-on: https://codereview.qt-project.org/c/qt/qtwebengine-chromium/+/600431
Reviewed-by: Qt Cherry-pick Bot <[email protected]>

Author: mnegyokru

chromium/media/filters/ffmpeg_audio_decoder.cc

@@ -368,6 +368,9 @@ bool FFmpegAudioDecoder::ConfigureDecoder(const AudioDecoderConfig& config) {
   const AVCodec* codec = [&config, this]() {
     if (config.codec() == AudioCodec::kOpus)
       return avcodec_find_decoder_by_name("libopus");
+    if (config.codec() == AudioCodec::kMP3) {
+      return avcodec_find_decoder_by_name("mp3");
+    }
     return avcodec_find_decoder(codec_context_->codec_id);
   }();
 #else

chromium/media/filters/ffmpeg_glue.cc

@@ -246,6 +246,24 @@ bool FFmpegGlue::OpenContext(bool is_local_file) {
   CHECK_NE(container_, container_names::MediaContainerName::kContainerUnknown);
   LogContainer(is_local_file, container_);
 
+#if BUILDFLAG(IS_QTWEBENGINE) && BUILDFLAG(USE_SYSTEM_FFMPEG)
+  // Sometimes FFmpeg is not aware of the whitelisted codecs and
+  // configures streams and demuxers with unsupported codecs/params.
+  // Force the correct codecs to avoid problems later.
+  // https://ffmpeg.org/doxygen/7.0/structAVFormatContext.html#a52f39351b15890ef57cc6ff0ec9ab42d
+  // https://ffmpeg.org/doxygen/7.0/structAVFormatContext.html#ae5e087f4623b907517c0f7dd8327387d
+
+  // Note: don't forget to update FFmpeg[Audio|Video]Decoder::ConfigureDecoder
+
+  if (strcmp(format_context_->iformat->name, "mp3") == 0) {
+    const AVCodec* mp3_codec = avcodec_find_decoder_by_name("mp3");
+    if (mp3_codec) {
+      format_context_->audio_codec = mp3_codec;
+    } else {
+      LOG(ERROR) << "No supported codec for mp3";
+    }
+  }
+#endif
   return true;
 }