Use ffmpeg for opus decoding, no need to maintain our decoder.

media/filters/ffmpeg_audio_decoder.cc

 // Copyright (c) 2012 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/filters/ffmpeg_audio_decoder.h"
 
 #include <stdint.h>
 
 #include "base/callback_helpers.h"
 #include "base/single_thread_task_runner.h"
@@ skipping 385 matching lines @@
   ReleaseFFmpegResources();
 
   // Initialize AVCodecContext structure.
   codec_context_.reset(avcodec_alloc_context3(NULL));
   AudioDecoderConfigToAVCodecContext(config_, codec_context_.get());
 
   codec_context_->opaque = this;
   codec_context_->get_buffer2 = GetAudioBuffer;
   codec_context_->refcounted_frames = 1;
 
+  if (config_.codec() == kCodecOpus)
+    codec_context_->request_sample_fmt = AV_SAMPLE_FMT_FLT;
+
   AVCodec* codec = avcodec_find_decoder(codec_context_->codec_id);
   if (!codec || avcodec_open2(codec_context_.get(), codec, NULL) < 0) {
     DLOG(ERROR) << "Could not initialize audio decoder: "
                 << codec_context_->codec_id;
     ReleaseFFmpegResources();
     state_ = kUninitialized;
     return false;
   }
 
   // Success!
   av_frame_.reset(av_frame_alloc());
   av_sample_format_ = codec_context_->sample_fmt;
 
   if (codec_context_->channels !=
       ChannelLayoutToChannelCount(config_.channel_layout())) {
     DLOG(ERROR) << "Audio configuration specified "
                 << ChannelLayoutToChannelCount(config_.channel_layout())
                 << " channels, but FFmpeg thinks the file contains "
                 << codec_context_->channels << " channels";
     ReleaseFFmpegResources();
     state_ = kUninitialized;
     return false;
   }
 
   ResetTimestampState();
   return true;
 }
 
 void FFmpegAudioDecoder::ResetTimestampState() {
-  discard_helper_.reset(new AudioDiscardHelper(config_.samples_per_second(),
-                                               config_.codec_delay()));
-  discard_helper_->Reset(config_.codec_delay());
+  // Opus codec delay is handled by ffmpeg.
+  const int codec_delay =
+      config_.codec() == kCodecOpus ? 0 : config_.codec_delay();
+  discard_helper_.reset(
+      new AudioDiscardHelper(config_.samples_per_second(), codec_delay,
+                             config_.codec() == kCodecVorbis));
+  discard_helper_->Reset(codec_delay);
 }
 
 }  // namespace media