Bug 881092 - Allow decoding files we know we can't play, in the context of WebAudio. r=kinetik,rillian

content/media/MediaDecoderReader.cpp

@@ -382,7 +382,8 @@ void* MediaDecoderReader::VideoQueueMemoryFunctor::operator()(void* anObject) {
 }
 
 MediaDecoderReader::MediaDecoderReader(AbstractMediaDecoder* aDecoder)
-  : mDecoder(aDecoder)
+  : mDecoder(aDecoder),
+    mIgnoreAudioBackendFormat(false)
 {
   MOZ_COUNT_CTOR(MediaDecoderReader);
 }

content/media/MediaDecoderReader.h

@@ -467,6 +467,14 @@ public:
   // decode thread could start up and run in future.
   virtual void OnDecodeThreadFinish() {}
 
+  // Tell the reader that the data decoded are not for direct playback, so it
+  // can accept more files, in particular those which have more channels than
+  // available in the audio output.
+  void SetIgnoreAudioOutputFormat()
+  {
+    mIgnoreAudioOutputFormat = true;
+  }
+
 protected:
   // Queue of audio frames. This queue is threadsafe, and is accessed from
   // the audio, decoder, state machine, and main threads.
@@ -543,6 +551,11 @@ protected:
 
   // Stores presentation info required for playback.
   VideoInfo mInfo;
+
+  // Whether we should accept media that we know we can't play
+  // directly, because they have a number of channel higher than
+  // what we support.
+  bool mIgnoreAudioOutputFormat;
 };
 
 } // namespace mozilla

content/media/wave/WaveReader.cpp

@@ -61,7 +61,8 @@ static const uint16_t WAVE_FORMAT_CHUNK_SIZE = 16;
 // supported by AudioStream.
 static const uint16_t WAVE_FORMAT_ENCODING_PCM = 1;
 
-// Maximum number of channels supported
+// We reject files with more than this number of channels if we're decoding for
+// playback.
 static const uint8_t MAX_CHANNELS = 2;
 
 namespace {
@@ -430,11 +431,13 @@ WaveReader::LoadFormatChunk(uint32_t aChunkSize)
 
   // Make sure metadata is fairly sane.  The rate check is fairly arbitrary,
   // but the channels check is intentionally limited to mono or stereo
-  // because that's what the audio backend currently supports.
+  // when the media is intended for direct playback because that's what the
+  // audio backend currently supports.
   unsigned int actualFrameSize = sampleFormat == 8 ? 1 : 2 * channels;
   if (rate < 100 || rate > 96000 ||
-      channels < 1 || channels > MAX_CHANNELS ||
-      (frameSize != 1 && frameSize != 2 && frameSize != 4) ||
+      (((channels < 1 || channels > MAX_CHANNELS) ||
+       (frameSize != 1 && frameSize != 2 && frameSize != 4)) &&
+       !mIgnoreAudioBackendFormat) ||
        (sampleFormat != 8 && sampleFormat != 16) ||
       frameSize != actualFrameSize) {
     NS_WARNING("Invalid WAVE metadata");

content/media/webaudio/MediaBufferDecoder.cpp

@@ -508,6 +508,11 @@ MediaDecodeTask::Decode()
 
   mBufferDecoder->BeginDecoding(NS_GetCurrentThread());
 
+  // Tell the decoder reader that we are not going to play the data directly,
+  // and that we should not reject files with more channels than the audio
+  // bakend support.
+  mDecoderReader->SetIgnoreAudioOutputFormat();
+
   mDecoderReader->OnDecodeThreadStart();
 
   VideoInfo videoInfo;