Introduce AudioDecoderConfig to migrate away from GetAVStream().

media/filters/ffmpeg_audio_decoder.cc

Index: media/filters/ffmpeg_audio_decoder.cc
diff --git a/media/filters/ffmpeg_audio_decoder.cc b/media/filters/ffmpeg_audio_decoder.cc
index cb3f846078329514071f4791569be5aa59b7b128..2cbcb4509b474eca69c7cf59fcd5f8768241fc1d 100644
--- a/media/filters/ffmpeg_audio_decoder.cc
+++ b/media/filters/ffmpeg_audio_decoder.cc
@@ -8,7 +8,6 @@
 #include "media/base/data_buffer.h"
 #include "media/base/demuxer.h"
 #include "media/base/filter_host.h"
-#include "media/base/limits.h"
 #include "media/ffmpeg/ffmpeg_common.h"
 
 namespace media {
@@ -58,6 +57,14 @@ FFmpegAudioDecoder::FFmpegAudioDecoder(MessageLoop* message_loop)
 
 FFmpegAudioDecoder::~FFmpegAudioDecoder() {
   av_free(decoded_audio_);
+
+  // XXX: should we require Stop() to be called? this might end up getting
+  // called on a random thread due to refcounting.
+  if (codec_context_) {
+    av_free(codec_context_->extradata);
+    avcodec_close(codec_context_);
+    av_free(codec_context_);
+  }
 }
 
 void FFmpegAudioDecoder::Flush(FilterCallback* callback) {
@@ -105,48 +112,39 @@ void FFmpegAudioDecoder::DoInitialize(
   scoped_ptr<FilterCallback> c(callback);
 
   demuxer_stream_ = stream;
-  AVStream* av_stream = demuxer_stream_->GetAVStream();
-  CHECK(av_stream);
-
+  const AudioDecoderConfig& config = stream->audio_decoder_config();
   stats_callback_.reset(stats_callback);
 
-  // Grab the AVStream's codec context and make sure we have sensible values.
-  codec_context_ = av_stream->codec;
-  int bps = av_get_bits_per_sample_fmt(codec_context_->sample_fmt);
-  if (codec_context_->channels <= 0 ||
-      codec_context_->channels > Limits::kMaxChannels ||
-      (codec_context_->channel_layout == 0 && codec_context_->channels > 2) ||
-      bps <= 0 || bps > Limits::kMaxBitsPerSample ||
-      codec_context_->sample_rate <= 0 ||
-      codec_context_->sample_rate > Limits::kMaxSampleRate) {
+  if (!config.IsValidConfig()) {

[Ami GONE FROM CHROMIUM, 2011/09/20 20:34:50]

This is better, but my point was that it would be nicer if not every caller of
audio_decoder_config() needed to check the return value for validity.  Is there
no opportunity for erroring-out earlier, presumably during stream construction?

[scherkus (not reviewing), 2011/09/21 18:19:16]

You're right in that the correct place for this check is before this object is
even created, however I'm hesitant to toss more code into PipelineImpl at this
time as it needs a lot of loving itself

TODOing it up for now

     DLOG(ERROR) << "Invalid audio stream -"
-                << " channels: " << codec_context_->channels
-                << " channel layout:" << codec_context_->channel_layout
-                << " bps: " << bps
-                << " sample rate: " << codec_context_->sample_rate;
+                << " codec: " << config.codec()
+                << " channel layout: " << config.channel_layout()
+                << " bits per channel: " << config.bits_per_channel()
+                << " sample rate: " << config.sample_rate();
 
-    host()->SetError(PIPELINE_ERROR_DECODE);
+    host()->SetError(DECODER_ERROR_NOT_SUPPORTED);
     callback->Run();
     return;
   }
 
-  // Serialize calls to avcodec_open().
+  // Initialize AVCodecContext structure.
+  codec_context_ = avcodec_alloc_context();
+  AudioDecoderConfigToAVCodecContext(config, codec_context_);
+
   AVCodec* codec = avcodec_find_decoder(codec_context_->codec_id);
   if (!codec || avcodec_open(codec_context_, codec) < 0) {
     DLOG(ERROR) << "Could not initialize audio decoder: "
                 << codec_context_->codec_id;
 
-    host()->SetError(PIPELINE_ERROR_DECODE);
+    host()->SetError(DECODER_ERROR_NOT_SUPPORTED);
     callback->Run();
     return;
   }
 
   // Success!
-  bits_per_channel_ = av_get_bits_per_sample_fmt(codec_context_->sample_fmt);
-  channel_layout_ =
-      ChannelLayoutToChromeChannelLayout(codec_context_->channel_layout,
-                                         codec_context_->channels);
-  sample_rate_ = codec_context_->sample_rate;
+  bits_per_channel_ = config.bits_per_channel();
+  channel_layout_ = config.channel_layout();
+  sample_rate_ = config.sample_rate();
 
   callback->Run();
 }