MP4 support for Common Encryption 'cbcs' scheme.

media/formats/mp4/mp4_stream_parser.cc

Index: media/formats/mp4/mp4_stream_parser.cc
diff --git a/media/formats/mp4/mp4_stream_parser.cc b/media/formats/mp4/mp4_stream_parser.cc
index dbd736df941a6542415faa81490e0bb290ec448f..dc785d2ee87c5beb322abd7e863ea36240dc302e 100644
--- a/media/formats/mp4/mp4_stream_parser.cc
+++ b/media/formats/mp4/mp4_stream_parser.cc
@@ -17,6 +17,7 @@
 #include "base/time/time.h"
 #include "build/build_config.h"
 #include "media/base/audio_decoder_config.h"
+#include "media/base/encryption_scheme.h"
 #include "media/base/media_tracks.h"
 #include "media/base/media_util.h"
 #include "media/base/stream_parser_buffer.h"
@@ -33,6 +34,41 @@
 namespace media {
 namespace mp4 {
 
+namespace {
+
+EncryptionScheme GetEncryptionScheme(const ProtectionSchemeInfo& sinf) {
+  if (!sinf.HasSupportedScheme())
+    return Unencrypted();

[ddorwin, 2016/06/17 23:32:41]

Is that the best way to handle this? We know it is encrypted. Or is the caller
supposed to know to handle this as an unsupported scheme, in which case we
should comment this above this function?

[dougsteed, 2016/10/10 18:18:01]

Done.

+  FourCC fourCC = sinf.type.type;
+  EncryptionScheme::CipherMode mode = EncryptionScheme::CIPHER_MODE_UNENCRYPTED;
+  EncryptionScheme::Pattern pattern;
+  bool pattern_encryption = false;

[ddorwin, 2016/06/17 23:32:41]

nit: is_/uses_...

[dougsteed, 2016/10/10 18:18:02]

Done.

+  switch (fourCC) {
+    case FOURCC_CENC:
+      mode = EncryptionScheme::CIPHER_MODE_AES_CTR;
+      break;
+#if BUILDFLAG(ENABLE_CBCS_ENCRYPTION_SCHEME)
+    case FOURCC_CBCS:
+      mode = EncryptionScheme::CIPHER_MODE_AES_CBC;
+      pattern_encryption = true;
+      break;
+#endif
+    default:
+      DLOG(WARNING) << "Unsupported encryption scheme: " << fourCC;

[ddorwin, 2016/06/17 23:32:40]

Should this be a DCHECK based on line 40?

[dougsteed, 2016/10/10 18:18:02]

Done.

+      break;
+  }
+#if BUILDFLAG(ENABLE_CBCS_ENCRYPTION_SCHEME)
+  if (pattern_encryption) {
+    uint8_t crypt = sinf.info.track_encryption.default_crypt_byte_block;

[ddorwin, 2016/06/17 23:32:40]

ditto on "crypt"

[dougsteed, 2016/10/10 18:18:01]

as mentioned above, this is the term used in the standard.

+    uint8_t skip = sinf.info.track_encryption.default_skip_byte_block;
+    pattern = EncryptionScheme::Pattern(crypt, skip);
+  }
+#endif
+  return EncryptionScheme(mode, pattern);
+}
+
+}  // namespace
+
 MP4StreamParser::MP4StreamParser(const std::set<int>& audio_object_types,
                                  bool has_sbr)
     : state_(kWaitingForInit),
@@ -316,7 +352,8 @@ bool MP4StreamParser::ParseMoov(BoxReader* reader) {
       DVLOG(1) << "is_audio_track_encrypted_: " << is_audio_track_encrypted_;
       audio_config.Initialize(
           codec, sample_format, channel_layout, sample_per_second, extra_data,
-          is_audio_track_encrypted_ ? AesCtrEncryptionScheme() : Unencrypted(),
+          is_audio_track_encrypted_ ? GetEncryptionScheme(entry.sinf)

[ddorwin, 2016/06/17 23:32:40]

Continuing from line 41, we know it's encrypted, but if the scheme is not
recognized, we just say "unencrypted". We should probably fail in some way
rather than silently continuing, which will be harder to debug.

[dougsteed, 2016/10/10 18:18:01]

Done.

+                                    : Unencrypted(),
           base::TimeDelta(), 0);
       has_audio_ = true;
       audio_track_id_ = track->header.track_id;
@@ -368,7 +405,8 @@ bool MP4StreamParser::ParseMoov(BoxReader* reader) {
           // No decoder-specific buffer needed for AVC;
           // SPS/PPS are embedded in the video stream
           EmptyExtraData(),
-          is_video_track_encrypted_ ? AesCtrEncryptionScheme() : Unencrypted());
+          is_video_track_encrypted_ ? GetEncryptionScheme(entry.sinf)
+                                    : Unencrypted());
       has_video_ = true;
       video_track_id_ = track->header.track_id;
       media_tracks->AddVideoTrack(
@@ -574,11 +612,9 @@ bool MP4StreamParser::EnqueueSample(BufferQueue* audio_buffers,
 
   if (decrypt_config) {
     if (!subsamples.empty()) {
-    // Create a new config with the updated subsamples.
-    decrypt_config.reset(new DecryptConfig(
-        decrypt_config->key_id(),
-        decrypt_config->iv(),
-        subsamples));
+      // Create a new config with the updated subsamples.
+      decrypt_config.reset(new DecryptConfig(decrypt_config->key_id(),
+                                             decrypt_config->iv(), subsamples));
     }
     // else, use the existing config.
   } else if ((audio && is_audio_track_encrypted_) ||