Fixing bug that 8bit PCM stream is gabbled...

media/filters/ffmpeg_audio_decoder.cc

 // Copyright (c) 2009 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.
 
 #include "media/base/data_buffer.h"
 #include "media/filters/ffmpeg_audio_decoder.h"
 #include "media/filters/ffmpeg_common.h"
 #include "media/filters/ffmpeg_demuxer.h"
 
 namespace media {
@@ skipping 24 matching lines @@
     return false;
   }
   AVStream* av_stream = av_stream_provider->GetAVStream();
 
   // Grab the AVStream's codec context and make sure we have sensible values.
   codec_context_ = av_stream->codec;
   DCHECK_GT(codec_context_->channels, 0);
   DCHECK_GT(av_get_bits_per_sample_format(codec_context_->sample_fmt), 0);
   DCHECK_GT(codec_context_->sample_rate, 0);
 
-  // Set the media format.
+  // Grab the codec context from FFmpeg demuxer.
+  AVCodec* codec = avcodec_find_decoder(codec_context_->codec_id);
+  if (!codec || avcodec_open(codec_context_, codec) < 0) {
+    host_->Error(PIPELINE_ERROR_DECODE);
+    return false;
+  }
+
+  // When calling avcodec_find_decoder(), |codec_context_| might be altered by
+  // the decoder to give more accurate values of the output format of the
+  // decoder. So set the media format after a decoder is allocated.
   // TODO(hclam): Reuse the information provided by the demuxer for now, we may
   // need to wait until the first buffer is decoded to know the correct
   // information.
   media_format_.SetAsInteger(MediaFormat::kChannels, codec_context_->channels);
   media_format_.SetAsInteger(MediaFormat::kSampleBits,
       av_get_bits_per_sample_format(codec_context_->sample_fmt));
   media_format_.SetAsInteger(MediaFormat::kSampleRate,
       codec_context_->sample_rate);
   media_format_.SetAsString(MediaFormat::kMimeType,
       mime_type::kUncompressedAudio);
 
-  // Grab the codec context from FFmpeg demuxer.
-  AVCodec* codec = avcodec_find_decoder(codec_context_->codec_id);
-  if (!codec || avcodec_open(codec_context_, codec) < 0) {
-    host_->Error(PIPELINE_ERROR_DECODE);
-    return false;
-  }
-
   // Prepare the output buffer.
   output_buffer_.reset(static_cast<uint8*>(av_malloc(kOutputBufferSize)));
   if (!output_buffer_.get()) {
     host_->Error(PIPELINE_ERROR_OUT_OF_MEMORY);
     return false;
   }
   return true;
 }
 
 void FFmpegAudioDecoder::OnStop() {
@@ skipping 64 matching lines @@
 base::TimeDelta FFmpegAudioDecoder::CalculateDuration(size_t size) {
   int64 denominator = codec_context_->channels *
       av_get_bits_per_sample_format(codec_context_->sample_fmt) / 8 *
       codec_context_->sample_rate;
   double microseconds = size /
       (denominator / static_cast<double>(base::Time::kMicrosecondsPerSecond));
   return base::TimeDelta::FromMicroseconds(static_cast<int64>(microseconds));
 }
 
 }  // namespace