Support encrypted audio stream in demuxer.

media/webm/webm_cluster_parser.cc

Index: media/webm/webm_cluster_parser.cc
diff --git a/media/webm/webm_cluster_parser.cc b/media/webm/webm_cluster_parser.cc
index a6867bc07d9783c863325f9f84dd89705defcf2a..cf5c0fcf76335dd2eaecb63cb81a2326e67f62c9 100644
--- a/media/webm/webm_cluster_parser.cc
+++ b/media/webm/webm_cluster_parser.cc
@@ -26,8 +26,10 @@ static std::string GenerateCounterBlock(uint64 iv) {
 WebMClusterParser::WebMClusterParser(int64 timecode_scale,
                                      int audio_track_num,
                                      int video_track_num,
+                                     const std::string& audio_encryption_key_id,
                                      const std::string& video_encryption_key_id)
     : timecode_multiplier_(timecode_scale / 1000.0),
+      audio_encryption_key_id_(audio_encryption_key_id),
       video_encryption_key_id_(video_encryption_key_id),
       parser_(kWebMIdCluster, this),
       last_block_timecode_(-1),
@@ -198,24 +200,34 @@ bool WebMClusterParser::OnBlock(int track_num, int timecode,
     return false;
   }
 
+  Track* track = NULL;
+  std::string encryption_key_id;

[ddorwin, 2012/10/10 07:14:52]

const ref?

[xhwang, 2012/10/11 00:49:41]

Ref has to be initialized upon declaration. If we want to avoid this copy (of
16/32 bytes), I can do at line 215:

const std::string& encryption_key_id = track_num == audio_.track_num() ?
audio_encryption_key_id_ : video_encryption_key_id_;

which I feel isn't as clean as the current code. WDYT?

[ddorwin, 2012/10/11 05:18:22]

Oh, duh. Nevermind.

+  if (track_num == audio_.track_num()) {
+    track = &audio_;
+    encryption_key_id = audio_encryption_key_id_;
+  } else if (track_num == video_.track_num()) {
+    track = &video_;
+    encryption_key_id = video_encryption_key_id_;
+  } else {
+    DVLOG(1) << "Unexpected track number " << track_num;

[ddorwin, 2012/10/10 07:14:52]

I know this was copied from below, but it seems like it should be a
DLOG(WARNING). It would be nice to see we are processing bad content.

[acolwell GONE FROM CHROMIUM, 2012/10/10 16:00:06]

I don't think this condition is any more important than the other DVLOG()
messages that report errors so I'd rather keep this consistent with the other
log messages. 

If there is a desire to have a wholesale change on this front then I think that
should be a different CL.

+    return false;
+  }
+
   last_block_timecode_ = timecode;
 
   base::TimeDelta timestamp = base::TimeDelta::FromMicroseconds(
       (cluster_timecode_ + timecode) * timecode_multiplier_);
 
-  // Every encrypted Block has a signal byte and IV prepended to it. Current
-  // encrypted WebM request for comments specification is here
-  // http://wiki.webmproject.org/encryption/webm-encryption-rfc
-  bool is_track_encrypted =
-      track_num == video_.track_num() && !video_encryption_key_id_.empty();
-
   // The first bit of the flags is set when the block contains only keyframes.
   // http://www.matroska.org/technical/specs/index.html
   bool is_keyframe = (flags & 0x80) != 0;
   scoped_refptr<StreamParserBuffer> buffer =
       StreamParserBuffer::CopyFrom(data, size, is_keyframe);
 
-  if (is_track_encrypted) {
+  // Every encrypted Block has a signal byte and IV prepended to it. Current
+  // encrypted WebM request for comments specification is here
+  // http://wiki.webmproject.org/encryption/webm-encryption-rfc
+  if (!encryption_key_id.empty()) {
     uint8 signal_byte = data[0];
     int data_offset = sizeof(signal_byte);
 
@@ -252,14 +264,7 @@ bool WebMClusterParser::OnBlock(int track_num, int timecode,
         block_duration * timecode_multiplier_));
   }
 
-  if (track_num == audio_.track_num()) {
-    return audio_.AddBuffer(buffer);
-  } else if (track_num == video_.track_num()) {
-    return video_.AddBuffer(buffer);
-  }
-
-  DVLOG(1) << "Unexpected track number " << track_num;
-  return false;
+  return track->AddBuffer(buffer);
 }
 
 WebMClusterParser::Track::Track(int track_num)