FFmpegDemuxer should fall back to disabled streams for seeking

media/filters/ffmpeg_demuxer.h

 // 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.
 
 // Implements the Demuxer interface using FFmpeg's libavformat.  At this time
 // will support demuxing any audio/video format thrown at it.  The streams
 // output mime types audio/x-ffmpeg and video/x-ffmpeg and include an integer
 // key FFmpegCodecID which contains the CodecID enumeration value.  The CodecIDs
 // can be used to create and initialize the corresponding FFmpeg decoder.
 //
@@ skipping 310 matching lines @@
   scoped_refptr<MediaLog> media_log_;
 
   // Derived bitrate after initialization has completed.
   int bitrate_;
 
   // The first timestamp of the audio or video stream, whichever is lower.  This
   // is used to adjust timestamps so that external consumers always see a zero
   // based timeline.
   base::TimeDelta start_time_;
 
+  // Finds the stream with the lowest known start time (i.e. not kNoTimestamp
+  // start time) with enabled status matching |enabled|.
+  FFmpegDemuxerStream* FindStreamWithLowestStartTimestamp(bool enabled);
+
   // Finds a preferred stream for seeking to |seek_time|. Preference is
   // typically given to video streams, unless the |seek_time| is earlier than
   // the start time of the video stream. In that case a stream with the earliest
-  // start time is preferred. Disabled streams are not considered.
+  // start time is preferred. Disabled streams are considered only as the last
+  // fallback option.
   FFmpegDemuxerStream* FindPreferredStreamForSeeking(base::TimeDelta seek_time);
 
   // The Time associated with timestamp 0. Set to a null
   // time if the file doesn't have an association to Time.
   base::Time timeline_offset_;
 
   // Whether text streams have been enabled for this demuxer.
   bool text_enabled_;
 
   // Set if we know duration of the audio stream. Used when processing end of
@@ skipping 14 matching lines @@
   base::WeakPtr<FFmpegDemuxer> weak_this_;
   base::WeakPtrFactory<FFmpegDemuxer> cancel_pending_seek_factory_;
   base::WeakPtrFactory<FFmpegDemuxer> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(FFmpegDemuxer);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_FILTERS_FFMPEG_DEMUXER_H_