Add AudioBufferStream.

media/base/audio_decoder.h

 // 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.
 
 #ifndef MEDIA_BASE_AUDIO_DECODER_H_
 #define MEDIA_BASE_AUDIO_DECODER_H_
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
+#include "media/base/audio_decoder_config.h"
 #include "media/base/channel_layout.h"
+#include "media/base/decoder_buffer.h"
+#include "media/base/media_export.h"
 #include "media/base/pipeline_status.h"
-#include "media/base/media_export.h"
 
 namespace media {
 
 class AudioBuffer;
 class DemuxerStream;
 
 class MEDIA_EXPORT AudioDecoder {
  public:
-  // Status codes for read operations.
+  // Status codes for decode operations.
   enum Status {
-    kOk,
-    kAborted,
-    kDecodeError,
+    kOk,  // We're all good.
+    kAborted,  // We aborted as a result of Stop() or Reset().
+    kNotEnoughData,  // Not enough data to produce a video frame.
+    kDecodeError,  // A decoding error occurred.
+    kDecryptError  // Decrypting error happened.
   };
 
   AudioDecoder();
   virtual ~AudioDecoder();
 
   // Initializes an AudioDecoder with the given DemuxerStream, executing the
   // callback upon completion.
   // statistics_cb is used to update global pipeline statistics.
-  virtual void Initialize(DemuxerStream* stream,
-                          const PipelineStatusCB& status_cb,
-                          const StatisticsCB& statistics_cb) = 0;
+  virtual void Initialize(const AudioDecoderConfig& config,
+                          const PipelineStatusCB& status_cb) = 0;
 
   // Requests samples to be decoded and returned via the provided callback.
   // Only one read may be in flight at any given time.
   //
   // Implementations guarantee that the callback will not be called from within
   // this method.
   //
   // Non-NULL sample buffer pointers will contain decoded audio data or may
   // indicate the end of the stream. A NULL buffer pointer indicates an aborted
   // Read(). This can happen if the DemuxerStream gets flushed and doesn't have
   // any more data to return.
   typedef base::Callback<void(Status, const scoped_refptr<AudioBuffer>&)>
-      ReadCB;
-  virtual void Read(const ReadCB& read_cb) = 0;
+      DecodeCB;
+  virtual void Decode(const scoped_refptr<DecoderBuffer>& buffer,
+                      const DecodeCB& decode_cb) = 0;
 
   // Resets decoder state, dropping any queued encoded data.
   virtual void Reset(const base::Closure& closure) = 0;
 
   // Stops decoder, fires any pending callbacks and sets the decoder to an
   // uninitialized state. An AudioDecoder cannot be re-initialized after it has
   // been stopped.
   // Note that if Initialize() has been called, Stop() must be called and
   // complete before deleting the decoder.
   virtual void Stop(const base::Closure& closure) = 0;
 
+  // Returns true if the decoder currently has the ability to decode and return
+  // an AudioBuffer. Most implementations can allocate a new AudioBuffer and
+  // hence this will always return true. Override and return false for decoders
+  // that use a fixed set of AudioBuffers for decoding.
+  virtual bool CanReadWithoutStalling() const;

[rileya (GONE FROM CHROMIUM), 2014/02/19 22:37:51]

Borrowed this from VideoDecoder, this will be always false for now, but this
makes the Decoder interfaces match better, and may one day be useful for some
AudioDecoder... (the alternative is having a few more template specializations
elsewhere).

+
   // Returns various information about the decoded audio format.
   virtual int bits_per_channel() = 0;
   virtual ChannelLayout channel_layout() = 0;
   virtual int samples_per_second() = 0;
 
+  // Some AudioDecoders will get multiple AudioBuffers out of a single
+  // DecoderBuffer, if this returns true, then the client should call Decode()
+  // with null DecoderBuffers until this returns false.
+  virtual bool HasQueuedData() const;

[rileya (GONE FROM CHROMIUM), 2014/02/19 22:37:51]

This seems like a clunky way of doing this... Another way of doing this that I
considered was returning a kHasMoreData status code from Decode, to signify that
we have queued data that needs to be exhausted before we want another
DecoderBuffer (but that seemed even worse than this, since the DecoderStream
would have to remember that for the next Read() call...).

I'm open to suggestions here...

+
  private:
   DISALLOW_COPY_AND_ASSIGN(AudioDecoder);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_AUDIO_DECODER_H_