Fix seeking when the start time is non-zero.

media/filters/ffmpeg_demuxer.h

Index: media/filters/ffmpeg_demuxer.h
diff --git a/media/filters/ffmpeg_demuxer.h b/media/filters/ffmpeg_demuxer.h
index 02682bbc8b2c38c4b3a07771a7c86558c595bfb9..ca38f1b92294f345235e16be1d68f1144c74fc46 100644
--- a/media/filters/ffmpeg_demuxer.h
+++ b/media/filters/ffmpeg_demuxer.h
@@ -23,6 +23,7 @@
 #define MEDIA_FILTERS_FFMPEG_DEMUXER_H_
 
 #include <string>
+#include <utility>
 #include <vector>
 
 #include "base/callback.h"
@@ -55,9 +56,14 @@ typedef scoped_ptr<AVPacket, ScopedPtrAVFreePacket> ScopedAVPacket;
 
 class FFmpegDemuxerStream : public DemuxerStream {
  public:
-  // Keeps a copy of |demuxer| and initializes itself using information
-  // inside |stream|.  Both parameters must outlive |this|.
-  FFmpegDemuxerStream(FFmpegDemuxer* demuxer, AVStream* stream);
+  // Keeps a copy of |demuxer| and initializes itself using information inside
+  // |stream|.  Both parameters must outlive |this|.
+  // |discard_negative_timestamps| tells the DemuxerStream that all packets with
+  // negative timestamps should be marked for post-decode discard.  All decoded
+  // data before time zero will be discarded.
+  FFmpegDemuxerStream(FFmpegDemuxer* demuxer,
+                      AVStream* stream,
+                      bool discard_negative_timestamps);
   virtual ~FFmpegDemuxerStream();
 
   // Enqueues the given AVPacket. It is invalid to queue a |packet| after
@@ -74,8 +80,7 @@ class FFmpegDemuxerStream : public DemuxerStream {
   // Empties the queues and ignores any additional calls to Read().
   void Stop();
 
-  // Returns the duration of this stream.
-  base::TimeDelta duration();
+  base::TimeDelta duration() const { return duration_; }
 
   // DemuxerStream implementation.
   virtual Type type() OVERRIDE;
@@ -136,6 +141,7 @@ class FFmpegDemuxerStream : public DemuxerStream {
   bool bitstream_converter_enabled_;
 
   std::string encryption_key_id_;
+  const bool discard_negative_timestamps_;
 
   DISALLOW_COPY_AND_ASSIGN(FFmpegDemuxerStream);
 };
@@ -155,7 +161,6 @@ class MEDIA_EXPORT FFmpegDemuxer : public Demuxer {
   virtual void Stop(const base::Closure& callback) OVERRIDE;
   virtual void Seek(base::TimeDelta time, const PipelineStatusCB& cb) OVERRIDE;
   virtual DemuxerStream* GetStream(DemuxerStream::Type type) OVERRIDE;
-  virtual base::TimeDelta GetStartTime() const OVERRIDE;
   virtual base::Time GetTimelineOffset() const OVERRIDE;
   virtual Liveness GetLiveness() const OVERRIDE;
 
@@ -168,6 +173,10 @@ class MEDIA_EXPORT FFmpegDemuxer : public Demuxer {
   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.
+  base::TimeDelta start_time() const { return start_time_; }
+
  private:
   // To allow tests access to privates.
   friend class FFmpegDemuxerTest;
@@ -224,7 +233,7 @@ class MEDIA_EXPORT FFmpegDemuxer : public Demuxer {
   // results of pre-seek av_read_frame() operations.
   bool pending_seek_;
 
-  // |streams_| mirrors the AVStream array in |format_context_|. It contains
+  // |streams_| mirrors the AVStream array in AVFormatContext. It contains
   // FFmpegDemuxerStreams encapsluating AVStream objects at the same index.
   //
   // Since we only support a single audio and video stream, |streams_| will
@@ -245,11 +254,22 @@ class MEDIA_EXPORT FFmpegDemuxer : public Demuxer {
   // Derived bitrate after initialization has completed.
   int bitrate_;
 
-  // The first timestamp of the opened media file. This is used to set the
-  // starting clock value to match the timestamps in the media file. Default
-  // is 0.
+  // 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_;
 
+  // The index and start time of the preferred streams for seeking.  Filled upon
+  // completion of OnFindStreamInfoDone().  Each info entry represents an index
+  // into |streams_| and the start time of that stream.
+  //
+  // Seek() will attempt to use |preferred_stream_for_seeking_| if the seek
+  // point occurs after its associated start time.  Otherwise it will use
+  // |fallback_stream_for_seeking_|.
+  typedef std::pair<int, base::TimeDelta> StreamSeekInfo;
+  StreamSeekInfo preferred_stream_for_seeking_;
+  StreamSeekInfo fallback_stream_for_seeking_;
+
   // 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_;