trying to do server side time seek on h264 mpegts media...

[Eric Trousset]

> -----Original Message-----
> From: Tim Müller [mailto:tim at centricular.com]
> Sent: mardi 12 novembre 2013 17:09
> To: gstreamer-devel at lists.freedesktop.org
> Subject: Re: trying to do server side time seek on h264 mpegts media...
> 
> On Tue, 2013-11-12 at 15:22 +0100, Eric Trousset wrote:
> 
> Hi Eric,
> 
> > As said in the title, I’m try to do et server side time seek on a
> > mpegts media.
> 
> Just to make sure: you mean you're doing something like
> 
>  gst-launch-1.0 playbin uri=http://example.com/path/to/foo.ts
> 
> ? Or are you using GStreamer server-side as well?

The server isn't using GStreamer. (as far as I know). And yes, I do a http request on the media

> 
> 
> > The initial seek is ok, eg I can start playing the media from anywhere
> > using the correct http header, the pipeline et build et the media
> > start playing ok. Thus, the query position, doesn’t take account of
> > the starting position. So this is one of my question, how do I tell
> > the pipeline that it didn’t start at position 0:00:00.000 but for
> > example at 0:00:30.000?
> 
> I'm not sure I understand your question here. What does a position query in
> TIME format return right after the seek has finished (ASYNC_DONE message
> on the bus)? And what did you expect it to return?

It returns 0:00:00.000, and I would like it to return 0:00:30.000

> 
> If you seek to 30s, the position query should report something around 30s
> when the seek is done.

The problem is that I am not seeking for the first request because I don't want to expose the fisrt image of the video. So I keep track of the starting point of the video, and do my first http request using this position as my start range. But then the pipeline think this is the position 0. So when resuming the playback of a movie, I don't have the correct time.

> 
> > Then, when I try to seek in the media, always using trickmodes, I can
> > some time get the first image of the new position, but with a lot of
> > artefacts. But then it freezes, and the ffmpegdec doesn’t produce
> > traces anymore.
> 
> What exactly do you mean with 'always using trickmodes' here? What kind of
> trickmodes? What exactly are you doing?

Lets say I want to jump forward 10s, I ask the pipeline the current position. And then I request the server for data at time = current_pos + 10s.
But then something seems to go wrong with the decoder. It stops decoding frames even after saying it has found a keyframe...

> 
> It sounds like it starts outputting data after the seek without waiting for a
> keyframe, which would explain the artefacts, but not the 'freezing'.

That is was I can't understand, according to the logs, it seems thing are going pretty well, but it somehow stops. 

> 
> What versions of things are you using? 0.10? 1.x? Which mpeg-ts demuxer
> ends up being used in your case? (there were at least three in 0.10 days).

I'm using 0.10.36. with flutsmpeg demuser

> 
> 
> > It looks like the pipeline is still in playing state reporting an
> > evolving position.
> 
> This would be expected after it first showed some frame again after the seek
> (with artefacts or without).
> 
> 
> > Anyone has a idea on how I can fix this?
> >
> > I tried setting the buffer flag to DISCONT, changing offset and/or
> > time stamps to some new values, with no results.
> 
> Tried doing this where? After a seek/flush, the first buffer should have the
> DISCONT flag set (but hopefully the decoders have already flushed
> everything anyway), but the demuxer should cater for that. Same for the
> timestamps on the buffers, the demuxer should just output the right thing
> there.

In the httpsrc (based on souphttpsrc), when receiving chunks
Actually, should I set the buffer offset to some value after a seek?

> 
> Cheers
>  -Tim
> 
> --
> Tim Müller, Centricular Ltd - http://www.centricular.com
> 
> 
> 
> 
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