Ensure media's buffered ranges always have a range that includes currentTime.

media/filters/ffmpeg_demuxer.cc

Index: media/filters/ffmpeg_demuxer.cc
diff --git a/media/filters/ffmpeg_demuxer.cc b/media/filters/ffmpeg_demuxer.cc
index 16c5447ae65ffa122e9c4887d36dd6f5290545d2..f7a084a75d792304ff9aedb2aa800256970705fa 100644
--- a/media/filters/ffmpeg_demuxer.cc
+++ b/media/filters/ffmpeg_demuxer.cc
@@ -30,9 +30,12 @@ namespace media {
 //
 // FFmpegDemuxerStream
 //
-FFmpegDemuxerStream::FFmpegDemuxerStream(FFmpegDemuxer* demuxer,
-                                         AVStream* stream)
-    : demuxer_(demuxer),
+FFmpegDemuxerStream::FFmpegDemuxerStream(
+    const NotifyBufferedCB& notify_buffered_cb,
+    FFmpegDemuxer* demuxer,
+    AVStream* stream)
+    : notify_buffered_cb_(notify_buffered_cb),
+      demuxer_(demuxer),
       stream_(stream),
       type_(UNKNOWN),
       discontinuous_(false),
@@ -92,8 +95,17 @@ void FFmpegDemuxerStream::EnqueuePacket(
     buffer = DecoderBuffer::CopyFrom(packet->data, packet->size);
     buffer->SetTimestamp(ConvertStreamTimestamp(
         stream_->time_base, packet->pts));
-    buffer->SetDuration(ConvertStreamTimestamp(
-        stream_->time_base, packet->duration));
+    buffer->SetDuration(std::max(
+        base::TimeDelta(), ConvertStreamTimestamp(

[scherkus (not reviewing), 2012/06/21 21:57:04]

this means duration can no longer be kNoTimestamp() -- we shouldn't change that
behaviour as a 0 duration implies that the duration is known to be 0 as opposed
to being unknown (i.e,. requires decoding the audio buffer to get the true
duration)

[Ami GONE FROM CHROMIUM, 2012/06/21 22:49:02]

That's interesting that you say that.
What would you say if I told you I saw negative durations come out of ffmpeg?
Because I would totally tell you this.
(triggered the DCHECK_LT(start, end) in Ranges::Add(start,end) in DRT /
layouttests)

Where do you think we use this kNoTimestamp?

[scherkus (not reviewing), 2012/06/21 22:58:22]

How negative were these durations? Were they −9,223,372,036,854,775,808 or
something else?

I know FFAD::IsTimestampMarkerPacket() checks for it but that's about it

[Ami GONE FROM CHROMIUM, 2012/06/21 23:18:11]

They were between 0 and -1.
Hmm.
ok, dropping.

+            stream_->time_base, packet->duration)));
+    if (last_packet_timestamp_ > base::TimeDelta() &&

[scherkus (not reviewing), 2012/06/21 21:57:04]

timestamps can be negative -- do you mean to check for kNoTimestamp()?

[Ami GONE FROM CHROMIUM, 2012/06/21 22:49:02]

No, I meant to check for TimeDelta() (to detect a flush as a proxy for a seek). 
Done.

[scherkus (not reviewing), 2012/06/21 22:58:22]

Why not use kNoTS() to detect a flush isntead of zero (which is a valid
timestamp)?

[Ami GONE FROM CHROMIUM, 2012/06/21 23:18:11]

Done.

+        last_packet_timestamp_ < buffer->GetTimestamp()) {
+      DCHECK(buffer->GetDuration() >= base::TimeDelta())

[scherkus (not reviewing), 2012/06/21 21:57:04]

ditto around here

[Ami GONE FROM CHROMIUM, 2012/06/21 22:49:02]

This is leftover from debugging the aforementioned DRT crashes.  Gone.

+          << buffer->GetDuration().ToInternalValue();
+      notify_buffered_cb_.Run(last_packet_timestamp_,
+                              buffer->GetTimestamp() + buffer->GetDuration());
+    }
+    last_packet_timestamp_ = buffer->GetTimestamp();
   }
 
   buffer_queue_.push_back(buffer);
@@ -106,6 +118,7 @@ void FFmpegDemuxerStream::FlushBuffers() {
   base::AutoLock auto_lock(lock_);
   DCHECK(read_queue_.empty()) << "Read requests should be empty";
   buffer_queue_.clear();
+  last_packet_timestamp_ = base::TimeDelta();

[scherkus (not reviewing), 2012/06/21 21:57:04]

kNoTS() here + ctor initializer list?

 }
 
 void FFmpegDemuxerStream::Stop() {
@@ -507,7 +520,10 @@ void FFmpegDemuxer::InitializeTask(DemuxerHost* host,
 
     AVStream* stream = format_context_->streams[i];
     scoped_refptr<FFmpegDemuxerStream> demuxer_stream(
-        new FFmpegDemuxerStream(this, stream));
+        new FFmpegDemuxerStream(
+            base::Bind(&DemuxerHost::AddBufferedTimeRange,
+                       base::Unretained(host_)),
+            this, stream));
 
     streams_[i] = demuxer_stream;
     max_duration = std::max(max_duration, demuxer_stream->duration());
@@ -638,6 +654,7 @@ void FFmpegDemuxer::DemuxTask() {
       (!audio_disabled_ ||
        streams_[packet->stream_index]->type() != DemuxerStream::AUDIO)) {
     FFmpegDemuxerStream* demuxer_stream = streams_[packet->stream_index];
+
     demuxer_stream->EnqueuePacket(packet.Pass());
   }