Motown: ffmpeg implementations of framework 'parts'

services/media/framework_ffmpeg/ffmpeg_audio_decoder.h

+// Copyright 2016 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 SERVICES_MEDIA_FRAMEWORK_FFMPEG_FFMPEG_AUDIO_DECODER_H_
+#define SERVICES_MEDIA_FRAMEWORK_FFMPEG_FFMPEG_AUDIO_DECODER_H_
+
+#include "services/media/framework/lpcm_util.h"
+#include "services/media/framework_ffmpeg/ffmpeg_decoder_base.h"
+
+namespace mojo {
+namespace media {
+
+// Decoder implementation employing an ffmpeg audio decoder.
+class FfmpegAudioDecoder : public FfmpegDecoderBase {
+ public:
+  FfmpegAudioDecoder(AVCodecContext *av_codec_context);
+
+  ~FfmpegAudioDecoder() override;
+
+ protected:
+  // FfmpegDecoderBase overrides.
+  int Decode(PayloadAllocator* allocator, bool* frame_decoded_out) override;
+
+  PacketPtr CreateOutputPacket(PayloadAllocator* allocator) override;
+
+ private:
+  // Align sample buffers on 32-byte boundaries. This is the value that Chromium
+  // uses and is supposed to work for all processor architectures. Strangely, if
+  // we were to tell ffmpeg to use the default (by passing 0), it aligns on 32
+  // sample (not byte) boundaries.
+  static const int kChannelAlign = 32;
+
+  // Callback used by the ffmpeg decoder to acquire a buffer.
+  static int AllocateBufferForAvFrame(
+      AVCodecContext* av_codec_context,
+      AVFrame* av_frame,
+      int flags);
+
+  // Callback used by the ffmpeg decoder to release a buffer.
+  static void ReleaseBufferForAvFrame(void* opaque, uint8_t* buffer);
+
+  // Set only for the duration of avcodec_decode_audio4 to provide context for
+  // AllocateBufferForAvFrame and ReleaseBufferForAvFrame.
+  PayloadAllocator* allocator_;
+
+  // AllocateBufferForAvFrame deposits the packet size here, because there's
+  // no good evidence of it after avcodec_decode_audio4 completes.
+  uint64_t packet_size_;
+
+  // This is used to verify that an allocated buffer is being used as expected
+  // by ffmpeg avcodec_decode_audio4. AllocateBufferForAvFrame sets it.
+  void* packet_buffer_;
+
+  // For interleaving, if needed.
+  std::unique_ptr<LpcmUtil> lpcm_util_;
+
+  // For interleaving, if needed.
+  std::unique_ptr<StreamType> stream_type_;
+};
+
+}  // namespace media
+}  // namespace mojo
+
+#endif // SERVICES_MEDIA_FRAMEWORK_FFMPEG_FFMPEG_AUDIO_DECODER_H_