Introduce AudioDecoderConfig to migrate away from GetAVStream().

media/ffmpeg/ffmpeg_common.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_FFMPEG_FFMPEG_COMMON_H_
 #define MEDIA_FFMPEG_FFMPEG_COMMON_H_
 
 // Used for FFmpeg error codes.
 #include <cerrno>
 
 #include "base/compiler_specific.h"
 #include "base/memory/singleton.h"
 #include "base/time.h"
+#include "media/base/audio_decoder_config.h"
 #include "media/base/channel_layout.h"
 #include "media/base/media_export.h"
 #include "media/video/video_decode_engine.h"
 
 // Include FFmpeg header files.
 extern "C" {
 // Temporarily disable possible loss of data warning.
 // TODO(scherkus): fix and upstream the compiler warnings.
 MSVC_PUSH_DISABLE_WARNING(4244);
 #include <libavcodec/avcodec.h>
@@ skipping 34 matching lines @@
 MEDIA_EXPORT base::TimeDelta ConvertFromTimeBase(const AVRational& time_base,
                                                  int64 timestamp);
 
 // Converts a base::TimeDelta into an int64 timestamp in |time_base| units.
 // For example if |timestamp| is 0.5 seconds and |time_base| is {1, 44100}, then
 // the return value will be 22050 since that is how many 1/44100ths of a second
 // represent 0.5 seconds.
 MEDIA_EXPORT int64 ConvertToTimeBase(const AVRational& time_base,
                                      const base::TimeDelta& timestamp);
 
+void AVCodecContextToAudioDecoderConfig(
+    const AVCodecContext* codec_context,
+    AudioDecoderConfig* config);
+void AudioDecoderConfigToAVCodecContext(
+    const AudioDecoderConfig& config,
+    AVCodecContext* codec_context);
+
 VideoCodec CodecIDToVideoCodec(CodecID codec_id);
 CodecID VideoCodecToCodecID(VideoCodec video_codec);
 
 // Converts FFmpeg's channel layout to chrome's ChannelLayout.  |channels| can
 // be used when FFmpeg's channel layout is not informative in order to make a
 // good guess about the plausible channel layout based on number of channels.
 ChannelLayout ChannelLayoutToChromeChannelLayout(int64_t layout,
                                                  int channels);
 
 // Calculates duration of one frame in the |stream| based on its frame rate.
@@ skipping 32 matching lines @@
 int GetNaturalHeight(AVStream* stream);
 int GetNaturalWidth(AVStream* stream);
 
 // Closes & destroys all AVStreams in the context and then closes &
 // destroys the AVFormatContext.
 void DestroyAVFormatContext(AVFormatContext* format_context);
 
 }  // namespace media
 
 #endif  // MEDIA_FFMPEG_FFMPEG_COMMON_H_