Add AudioBufferStream.

media/base/audio_decoder.h

Index: media/base/audio_decoder.h
diff --git a/media/base/audio_decoder.h b/media/base/audio_decoder.h
index 5aefb84aa67e486971f5836cbdccb3e338abdb08..12ce075aeb26b885c3ef2a47ca19ccc680d7ba51 100644
--- a/media/base/audio_decoder.h
+++ b/media/base/audio_decoder.h
@@ -7,9 +7,11 @@
 
 #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/pipeline_status.h"
+#include "media/base/decoder_buffer.h"
 #include "media/base/media_export.h"
+#include "media/base/pipeline_status.h"
 
 namespace media {
 
@@ -18,11 +20,13 @@ 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();
@@ -31,9 +35,8 @@ class MEDIA_EXPORT 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.
@@ -46,8 +49,9 @@ class MEDIA_EXPORT AudioDecoder {
   // 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;
@@ -59,11 +63,22 @@ class MEDIA_EXPORT AudioDecoder {
   // 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);
 };