Add support for encrypted WebM files as defined in the RFC.

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 6cbd71d8904fe75e30306b828e2cea112530238e..a7ec737b5e9553147b0dc7df6b9502c70300738f 100644
--- a/media/webm/webm_cluster_parser.cc
+++ b/media/webm/webm_cluster_parser.cc
@@ -5,6 +5,7 @@
 #include "media/webm/webm_cluster_parser.h"
 
 #include "base/logging.h"
+#include "base/sys_byteorder.h"
 #include "media/base/data_buffer.h"
 #include "media/base/decrypt_config.h"
 #include "media/webm/webm_constants.h"
@@ -184,17 +185,31 @@ bool WebMClusterParser::OnBlock(int track_num, int timecode,
 
   last_block_timecode_ = timecode;
 
-  base::TimeDelta timestamp = base::TimeDelta::FromMicroseconds(
+  const base::TimeDelta timestamp = base::TimeDelta::FromMicroseconds(
       (cluster_timecode_ + timecode) * timecode_multiplier_);

[xhwang, 2012/06/06 20:54:06]

I remember scherkus@ told me that in media stack code, we don't use const so
proactively. It's mostly used in const-ref parameter passing.

[fgalligan1, 2012/06/08 21:02:38]

Thanks for the info. Done.

 
+  const bool encrypted = track_num == video_.track_num() &&
+                         video_encryption_key_id_.get();
+
+  // Every encrypted Block has an HMAC and IV prepended to every encrypted
+  // frame.
+  const uint8* const frame_data =
+      encrypted ? data + kIntegrityCheckSize + kIVSize : data;
+  const int frame_size =
+      encrypted ? size - (kIntegrityCheckSize + kIVSize) : size;
+
   // 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;
+  const bool is_keyframe = (flags & 0x80) != 0;
   scoped_refptr<StreamParserBuffer> buffer =
-      StreamParserBuffer::CopyFrom(data, size, is_keyframe);
+      StreamParserBuffer::CopyFrom(frame_data, frame_size, is_keyframe);
 
-  if (track_num == video_.track_num() && video_encryption_key_id_.get()) {
+  if (encrypted) {
+    uint64 network_iv;
+    memcpy(&network_iv, data + kIntegrityCheckSize, sizeof(network_iv));
+    const uint64 iv = base::NetToHost64(network_iv);
     buffer->SetDecryptConfig(scoped_ptr<DecryptConfig>(new DecryptConfig(
+        data, kIntegrityCheckSize, iv,
         video_encryption_key_id_.get(), video_encryption_key_id_size_)));
   }