MP4 support for Common Encryption 'cbcs' scheme.

media/media_options.gni

Index: media/media_options.gni
diff --git a/media/media_options.gni b/media/media_options.gni
index 72f100e79c7512df9f605836c0e1256bdf627e5e..e54c57934a2a96437317db4beef374843e43ebf3 100644
--- a/media/media_options.gni
+++ b/media/media_options.gni
@@ -39,6 +39,12 @@ declare_args() {
 
   enable_mse_mpeg2ts_stream_parser = proprietary_codecs && is_chromecast
 
+  # Enable support for newer editions of MPEG Common Encryption (CENC)

[ddorwin, 2016/05/24 23:25:03]

This comment and variable (and define) name are inaccurate. This specifically
adds support for additional schemes. EME is by definition referencing 3rd
edition now, but only 'cenc' is currently supported in the registry. Thus, this
should be something like enable_additional_cenc_schemes. Or maybe just
enable_cbcs.

[dougsteed, 2016/05/25 17:23:21]

I see. In this name I had intended to mean 'cenc' as the abbreviation for the
"common encryption" standard, rather than the 'cenc' scheme itself. Quite
ambiguous.

+  # (ISO/IEC 23001-7).
+  # 2nd edition: was published 04/01/2015.
+  # 3rd edition: was published 02/15/2016.
+  enable_cenc_new_editions = is_chromecast
+
   # Enable HEVC/H265 demuxing. Actual decoding must be provided by the
   # platform. Enable by default for Chromecast.
   enable_hevc_demuxing = proprietary_codecs && is_chromecast