Simplify AudioSplicer logic which slots buffers before or after a splice point.

media/base/audio_splicer.h

Index: media/base/audio_splicer.h
diff --git a/media/base/audio_splicer.h b/media/base/audio_splicer.h
index 4d484d6de8893326c3529dcc2268519ddafdd663..389607ae2c2cc1046b6ba6ac79711a5b315907c5 100644
--- a/media/base/audio_splicer.h
+++ b/media/base/audio_splicer.h
@@ -45,10 +45,15 @@ class MEDIA_EXPORT AudioSplicer {
   // should only be called if HasNextBuffer() returns true.
   scoped_refptr<AudioBuffer> GetNextBuffer();
 
-  // Indicates that overlapping buffers are coming up and should be crossfaded.
-  // Once set, all buffers encountered after |splice_timestamp| will be queued
-  // internally until at least 5ms of overlapping buffers are received (or end
-  // of stream, whichever comes first).
+  // Indicates an upcoming splice point.  All buffers overlapping or after the
+  // |splice_timestamp| will be considered as "before the splice."  Clients must
+  // then call SetSpliceTimestamp(kNoTimestamp()) to signal that future buffers
+  // should be considered as "after the splice."
+  //
+  // Once |kCrossfadeDurationInMilliseconds| of buffers "after the splice" or
+  // end of stream has been received, the "after" buffers will be crossfaded
+  // with all "before" buffers which overlap them.  "before" buffers outside
+  // of the overlap range will be discarded.

[wolenetz, 2014/04/17 22:29:30]

This "discard" logic: where is it? I see that l.287 of audio_splicer.cc feeds
these to the output. By 'buffers', are decoded frames meant, instead (and the
discard happens in ExtractCrossfadeFromPreSplice()?)

[DaleCurtis, 2014/04/17 23:52:33]

The discard of unused pre splice buffers happens on l.475 of audio_splicer.cc 

   void SetSpliceTimestamp(base::TimeDelta splice_timestamp);
 
  private:
@@ -101,6 +106,10 @@ class MEDIA_EXPORT AudioSplicer {
   scoped_ptr<AudioStreamSanitizer> pre_splice_sanitizer_;
   scoped_ptr<AudioStreamSanitizer> post_splice_sanitizer_;
 
+  // Whether all buffers which should go into |pre_splice_sanitizer_| have been
+  // received.  If true, buffers should now be put in |post_splice_sanitizer_|.
+  bool have_all_pre_splice_buffers_;
+
   DISALLOW_IMPLICIT_CONSTRUCTORS(AudioSplicer);
 };