Providing unplayed bytes in audio hardware buffer

BUG=20007
TEST=WinAudioTest.PCMWaveStreamPendingBytes

We used to guess what is in the hardware audio buffer to
perform audio sync. But due the triple buffering and
other platforms has other buffering scheme we need to be
able to know how many bytes are left in the hardware buffer.

We provide this data via AudioCallback::OnMoreData(), so we
can predict when the requested buffer will be played.

Review URL: http://codereview.chromium.org/174243

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@24114 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 4 insertions, 2 deletions

diff --git a/media/audio/audio_output.h b/media/audio/audio_output.h
index f27858b..e6a1ee5 100644
--- a/media/audio/audio_output.h
+++ b/media/audio/audio_output.h
@@ -53,8 +53,10 @@ class AudioOutputStream {
     // buffer size is usually what is specified in Open(). The source
     // will return the number of bytes it filled. The expected structure of
     // |dest| is platform and format specific.
-    virtual size_t OnMoreData(AudioOutputStream* stream,
-                              void* dest, size_t max_size) = 0;
+    // |pending_bytes| is the number of bytes will be played before the
+    // requested data is played.
+    virtual size_t OnMoreData(AudioOutputStream* stream, void* dest,
+                              size_t max_size, int pending_bytes) = 0;
 
     // The stream is done with this callback. After this call the audio source
     // can go away or be destroyed.