Support encrypted audio stream in demuxer.

media/webm/webm_cluster_parser.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/webm/webm_cluster_parser.h"
 
 #include <vector>
 
 #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"
 
 namespace media {
 
 // Generates a 16 byte CTR counter block. The CTR counter block format is a
 // CTR IV appended with a CTR block counter. |iv| is an 8 byte CTR IV.
 // Returns a string of kDecryptionKeySize bytes.
 static std::string GenerateCounterBlock(uint64 iv) {
   std::string counter_block(reinterpret_cast<char*>(&iv), sizeof(iv));
   counter_block.append(DecryptConfig::kDecryptionKeySize - sizeof(iv), 0);
   return counter_block;
 }
 
 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),
       block_data_size_(-1),
       block_duration_(-1),
       cluster_timecode_(-1),
       cluster_start_time_(kNoTimestamp()),
       cluster_ended_(false),
       audio_(audio_track_num),
       video_(video_track_num) {
@@ skipping 150 matching lines @@
   if (timecode < 0) {
     DVLOG(1) << "Got a block with negative timecode offset " << timecode;
     return false;
   }
 
   if (last_block_timecode_ != -1 && timecode < last_block_timecode_) {
     DVLOG(1) << "Got a block with a timecode before the previous block.";
     return false;
   }
 
+  Track* track = NULL;
+  std::string encryption_key_id;
+  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;
+    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);
 
     // Setting the DecryptConfig object of the buffer while leaving the
     // initialization vector empty will tell the decryptor that the frame is
     // unencrypted.
     std::string counter_block;
 
     if (signal_byte & kWebMFlagEncryptedFrame) {
       uint64 network_iv;
       memcpy(&network_iv, data + data_offset, sizeof(network_iv));
-      const uint64 iv = base::NetToHost64(network_iv);
-      counter_block = GenerateCounterBlock(iv);
-      data_offset += sizeof(iv);
+      data_offset += sizeof(network_iv);
+      counter_block = GenerateCounterBlock(base::NetToHost64(network_iv));
     }
 
     // TODO(fgalligan): Revisit if DecryptConfig needs to be set on unencrypted
     // frames after the CDM API is finalized.
     // Unencrypted frames of potentially encrypted streams currently set
     // DecryptConfig.
     buffer->SetDecryptConfig(scoped_ptr<DecryptConfig>(new DecryptConfig(
-        video_encryption_key_id_,
+        encryption_key_id,
         counter_block,
         data_offset,
         std::vector<SubsampleEntry>())));
   }
 
   buffer->SetTimestamp(timestamp);
   if (cluster_start_time_ == kNoTimestamp())
     cluster_start_time_ = timestamp;
 
   if (block_duration >= 0) {
     buffer->SetDuration(base::TimeDelta::FromMicroseconds(
         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)
     : track_num_(track_num) {
 }
 
 WebMClusterParser::Track::~Track() {}
 
 bool WebMClusterParser::Track::AddBuffer(
     const scoped_refptr<StreamParserBuffer>& buffer) {
   DVLOG(2) << "AddBuffer() : " << track_num_
            << " ts " << buffer->GetTimestamp().InSecondsF()
            << " dur " << buffer->GetDuration().InSecondsF()
            << " kf " << buffer->IsKeyframe()
            << " size " << buffer->GetDataSize();
 
   buffers_.push_back(buffer);
   return true;
 }
 
 void WebMClusterParser::Track::Reset() {
   buffers_.clear();
 }
 
 }  // namespace media