media config: expand is_encrypted to a struct.

media/ffmpeg/ffmpeg_common.cc

Index: media/ffmpeg/ffmpeg_common.cc
diff --git a/media/ffmpeg/ffmpeg_common.cc b/media/ffmpeg/ffmpeg_common.cc
index 51e8884fedb1b35fab80b24e13abda6ae4c8f688..b2bf2c2ed35ffad884cd431232fabe39d4e1e8ad 100644
--- a/media/ffmpeg/ffmpeg_common.cc
+++ b/media/ffmpeg/ffmpeg_common.cc
@@ -13,6 +13,7 @@
 #include "build/build_config.h"
 #include "media/base/audio_decoder_config.h"
 #include "media/base/decoder_buffer.h"
+#include "media/base/encryption_scheme.h"
 #include "media/base/video_decoder_config.h"
 #include "media/base/video_util.h"
 #include "media/media_features.h"
@@ -371,13 +372,12 @@ bool AVCodecContextToAudioDecoderConfig(const AVCodecContext* codec_context,
     extra_data.assign(codec_context->extradata,
                       codec_context->extradata + codec_context->extradata_size);
   }
-  config->Initialize(codec,
-                     sample_format,
-                     channel_layout,
-                     sample_rate,
-                     extra_data,
-                     is_encrypted,
-                     seek_preroll,
+
+  EncryptionScheme encryption_scheme(

[ddorwin, 2016/03/02 23:24:05]

It's weird that the audio path has an extra function call. I'll look into that.
For now, though, it seems better for the code to be consistent (creating a
scheme rather than bool), and we should put this information as close to where
we processed the media data as possible. Thus, I suggest passing in a const
EncryptionScheme&.

Going further, we could abstract this to GetEncryptionScheme(const AVStream*
stream) so we don't even need to duplicate the metadata processing.

[dougsteed, 2016/03/03 04:45:00]

Done. The extra audio function AVCodecContextToAudioDecoderConfig is labelled
MEDIA_EXPORT.
OK to change the signature? (Although it only seems to be used in unit tests).

[ddorwin, 2016/03/03 18:38:04]

Yes. No interfaces are guaranteed not to change except things like PPAPI.

I found that the audio wrapper was added in
https://chromiumcodereview.appspot.com/10829470/diff/120001/media/ffmpeg/ffmp...
to make it match the video case. I think we can eliminate the internal function.
I'll look into it.

+      is_encrypted ? EncryptionScheme::kCipherModeAesCtr
+                   : EncryptionScheme::kCipherModeUnencrypted);
+  config->Initialize(codec, sample_format, channel_layout, sample_rate,
+                     extra_data, encryption_scheme, seek_preroll,
                      codec_context->delay);
 
   // Verify that AudioConfig.bits_per_channel was calculated correctly for
@@ -497,11 +497,11 @@ bool AVStreamToVideoDecoderConfig(const AVStream* stream,
       coded_size.set_height((coded_size.height() + 1) / 2 * 2);
   }
 
-  bool is_encrypted = false;
   AVDictionaryEntry* key =
       av_dict_get(stream->metadata, "enc_key_id", nullptr, 0);
-  if (key)
-    is_encrypted = true;
+  EncryptionScheme encryption_scheme(
+      key ? EncryptionScheme::kCipherModeAesCtr
+          : EncryptionScheme::kCipherModeUnencrypted);
 
   AVDictionaryEntry* webm_alpha =
       av_dict_get(stream->metadata, "alpha_mode", nullptr, 0);
@@ -535,7 +535,7 @@ bool AVStreamToVideoDecoderConfig(const AVStream* stream,
                       stream->codec->extradata + stream->codec->extradata_size);
   }
   config->Initialize(codec, profile, format, color_space, coded_size,
-                     visible_rect, natural_size, extra_data, is_encrypted);
+                     visible_rect, natural_size, extra_data, encryption_scheme);
   return true;
 }