Initialize media timeline correctly for positive start times.

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 150 matching lines @@
   virtual ~FFmpegDemuxer();
 
   // Demuxer implementation.
   virtual void Initialize(DemuxerHost* host,
                           const PipelineStatusCB& status_cb,
                           bool enable_text_tracks) OVERRIDE;
   virtual void Stop() OVERRIDE;
   virtual void Seek(base::TimeDelta time, const PipelineStatusCB& cb) OVERRIDE;
   virtual base::Time GetTimelineOffset() const OVERRIDE;
   virtual DemuxerStream* GetStream(DemuxerStream::Type type) OVERRIDE;
+  virtual base::TimeDelta GetStartTime() const OVERRIDE;
   virtual Liveness GetLiveness() const OVERRIDE;
 
   // Calls |need_key_cb_| with the initialization data encountered in the file.
   void FireNeedKey(const std::string& init_data_type,
                    const std::string& encryption_key_id);
 
   // Allow FFmpegDemuxerStream to notify us when there is updated information
   // about capacity and what buffered data is available.
   void NotifyCapacityAvailable();
   void NotifyBufferingChanged();
 
-  // The lowest demuxed timestamp.  DemuxerStream's must use this to adjust
-  // packet timestamps such that external clients see a zero-based timeline.
+  // The lowest demuxed timestamp.  If negative, DemuxerStreams must use this to
+  // adjust packet timestamps such that external clients see a zero-based
+  // timeline.
   base::TimeDelta start_time() const { return start_time_; }
 
  private:
   // To allow tests access to privates.
   friend class FFmpegDemuxerTest;
 
   // FFmpeg callbacks during initialization.
   void OnOpenContextDone(const PipelineStatusCB& status_cb, bool result);
   void OnFindStreamInfoDone(const PipelineStatusCB& status_cb, int result);
 
@@ skipping 101 matching lines @@
 
   // NOTE: Weak pointers must be invalidated before all other member variables.
   base::WeakPtrFactory<FFmpegDemuxer> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(FFmpegDemuxer);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_FILTERS_FFMPEG_DEMUXER_H_