Fix seeking when the start time is non-zero.

media/base/pipeline.cc

 // 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.
 
 #include "media/base/pipeline.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/callback.h"
@@ skipping 725 matching lines @@
     // TODO(scherkus): should we run the callback?  I'm tempted to say the API
     // will only execute the first Seek() request.
     DVLOG(1) << "Media pipeline has not started, ignoring seek to "
              << time.InMicroseconds() << " (current state: " << state_ << ")";
     return;
   }
 
   DCHECK(seek_cb_.is_null());
 
   SetState(kSeeking);
-  base::TimeDelta seek_timestamp = std::max(time, demuxer_->GetStartTime());
   seek_cb_ = seek_cb;
   audio_ended_ = false;
   video_ended_ = false;
   text_ended_ = false;
 
+  // Adjust the seek timestamp by the start time (which may be negative).  Don't
+  // use this value with SetTime() since it maps to a [0, duration] based
+  // timeline instead of a [start_time, duration + start_time] one internally.
+  const base::TimeDelta seek_timestamp = time + demuxer_->GetStartTime();
+
   // Kick off seeking!
   {
     base::AutoLock auto_lock(lock_);
     PauseClockAndStopRendering_Locked();
-    clock_->SetTime(seek_timestamp, seek_timestamp);
+    clock_->SetTime(time, time);

[acolwell GONE FROM CHROMIUM, 2014/06/09 23:14:46]

This makes me really nervous and I'm pretty sure it is wrong. I suspect this
will break A/V sync if the start time != 0 unless there is something that is
subtracting off the start time in the demuxer. You should definitely do tests
with muxed A/V content that starts at something significantly greater than 0
before landing this just to make sure you aren't breaking things.

   }
   DoSeek(seek_timestamp, base::Bind(
       &Pipeline::OnStateTransition, base::Unretained(this)));
 }
 
 void Pipeline::DoAudioRendererEnded() {
   DCHECK(task_runner_->BelongsToCurrentThread());
 
   if (state_ != kPlaying)
     return;
@@ skipping 210 matching lines @@
 void Pipeline::StartClockIfWaitingForTimeUpdate_Locked() {
   lock_.AssertAcquired();
   if (clock_state_ != CLOCK_WAITING_FOR_AUDIO_TIME_UPDATE)
     return;
 
   clock_state_ = CLOCK_PLAYING;
   clock_->Play();
 }
 
 }  // namespace media