MP4 support for Common Encryption 'cbcs' scheme.

media/formats/mp4/track_run_iterator.cc

Index: media/formats/mp4/track_run_iterator.cc
diff --git a/media/formats/mp4/track_run_iterator.cc b/media/formats/mp4/track_run_iterator.cc
index 7193b3d26dd9d5eb03b47ef298bc8d4d99ec11c6..98fcab3ac99f9dd977892be67b1236bc230b814a 100644
--- a/media/formats/mp4/track_run_iterator.cc
+++ b/media/formats/mp4/track_run_iterator.cc
@@ -12,6 +12,7 @@
 #include "base/macros.h"
 #include "media/formats/mp4/rcheck.h"
 #include "media/formats/mp4/sample_to_group_iterator.h"
+#include "media/media_features.h"
 
 namespace media {
 namespace mp4 {
@@ -282,11 +283,11 @@ bool TrackRunIterator::Init(const MovieFragment& moof) {
     const std::vector<uint8_t>& sample_encryption_data =
         traf.sample_encryption.sample_encryption_data;
     std::unique_ptr<BufferReader> sample_encryption_reader;
-    uint32_t sample_encrytion_entries_count = 0;
+    uint32_t sample_encryption_entries_count = 0;
     if (!sample_encryption_data.empty()) {
       sample_encryption_reader.reset(new BufferReader(
           sample_encryption_data.data(), sample_encryption_data.size()));
-      RCHECK(sample_encryption_reader->Read4(&sample_encrytion_entries_count));
+      RCHECK(sample_encryption_reader->Read4(&sample_encryption_entries_count));
     }
 
     // Process edit list to remove CTS offset introduced in the presence of
@@ -323,26 +324,23 @@ bool TrackRunIterator::Init(const MovieFragment& moof) {
       tri.fragment_sample_encryption_info =
           traf.sample_group_description.entries;
 
-      uint8_t default_iv_size = 0;
+      const TrackEncryption* track_encryption;
       tri.is_audio = (stsd.type == kAudio);
       if (tri.is_audio) {
         RCHECK(!stsd.audio_entries.empty());
         if (desc_idx > stsd.audio_entries.size())
           desc_idx = 0;
         tri.audio_description = &stsd.audio_entries[desc_idx];
-        default_iv_size =
-            tri.audio_description->sinf.info.track_encryption.default_iv_size;
+        track_encryption = &tri.audio_description->sinf.info.track_encryption;
       } else {
         RCHECK(!stsd.video_entries.empty());
         if (desc_idx > stsd.video_entries.size())
           desc_idx = 0;
         tri.video_description = &stsd.video_entries[desc_idx];
-        default_iv_size =
-            tri.video_description->sinf.info.track_encryption.default_iv_size;
+        track_encryption = &tri.video_description->sinf.info.track_encryption;
       }
-
       // Initialize aux_info variables only if no sample encryption entries.
-      if (sample_encrytion_entries_count == 0 &&
+      if (sample_encryption_entries_count == 0 &&
           traf.auxiliary_offset.offsets.size() > j) {
         // Collect information from the auxiliary_offset entry with the same
         // index in the 'saiz' container as the current run's index in the
@@ -402,18 +400,42 @@ bool TrackRunIterator::Init(const MovieFragment& moof) {
           RCHECK(GetSampleEncryptionInfoEntry(tri, index));
         is_sample_to_group_valid = sample_to_group_itr.Advance();
       }
-      if (sample_encrytion_entries_count > 0) {
-        RCHECK(sample_encrytion_entries_count >=
+      if (sample_encryption_entries_count > 0) {
+        RCHECK(sample_encryption_entries_count >=
                sample_count_sum + trun.sample_count);
         tri.sample_encryption_entries.resize(trun.sample_count);
         for (size_t k = 0; k < trun.sample_count; k++) {
           uint32_t index = tri.samples[k].cenc_group_description_index;
-          const uint8_t iv_size =
-              index == 0 ? default_iv_size
-                         : GetSampleEncryptionInfoEntry(tri, index)->iv_size;
-          RCHECK(tri.sample_encryption_entries[k].Parse(
-              sample_encryption_reader.get(), iv_size,
-              traf.sample_encryption.use_subsample_encryption));
+          const CencSampleEncryptionInfoEntry* info_entry =
+              index == 0 ? nullptr : GetSampleEncryptionInfoEntry(tri, index);
+          const uint8_t iv_size = index == 0 ? track_encryption->default_iv_size
+                                             : info_entry->iv_size;
+          SampleEncryptionEntry& entry = tri.sample_encryption_entries[k];
+          RCHECK(entry.Parse(sample_encryption_reader.get(), iv_size,
+                             traf.sample_encryption.use_subsample_encryption));
+#if BUILDFLAG(ENABLE_CBCS_ENCRYPTION_SCHEME)
+          // if we don't have a per-sample IV, get the constant IV.
+          if (!iv_size) {
+            const uint8_t constant_iv_size =
+                index == 0 ? track_encryption->default_constant_iv_size
+                           : info_entry->constant_iv_size;
+            RCHECK(constant_iv_size != 0);
+            const uint8_t* constant_iv =
+                index == 0 ? track_encryption->default_constant_iv
+                           : info_entry->constant_iv;
+            memcpy(entry.initialization_vector, constant_iv, constant_iv_size);
+          }
+          // We only support setting the pattern values in the 'tenc' box for
+          // the track (not varying on per sample group basis).
+          // Thus we need to verify that the settings in the sample group match
+          // those in the 'tenc'.
+          if (index != 0) {
+            RCHECK(info_entry->crypt_byte_block ==
+                   track_encryption->default_crypt_byte_block);
+            RCHECK(info_entry->skip_byte_block ==
+                   track_encryption->default_skip_byte_block);
+          }
+#endif

[kqyang, 2016/05/26 17:34:50]

Consider add a new unittest in track_run_iterator_unittest.cc

[dougsteed, 2016/06/09 22:38:27]

Done.

         }
       }

[kqyang, 2016/05/27 17:45:58]

The implementation here only supports the case when SampleEncryption 'senc' box
is present. However, according to the spec, 'senc' is optional and can be
omitted. For the case of 'senc' absent, can you either implement it or add a
logging stating that it is not implemented?

(when constant iv is applied to non video tracks, I am not sure if it is still
meaningful to generate 'senc' box which is empty; the spec says that the sample
auxiliary information would then be empty and should be omitted - it does not
say anything on 'senc' or 'saio' or 'saiz' explicitly though)

[dougsteed, 2016/06/09 22:38:27]

Done. I added code to cover the other cases.

       runs_.push_back(tri);