[gst-devel] Re : question on seek

[Wim Taymans]

On Fri, 2009-04-10 at 08:51 +0000, Albert Costa wrote:
> Thanks to all for the answers.
> So it looks like I can't avoid simply the prerolled frames, at least
> without significant code change. So I'll just let it be for the
> moment.
> Al

We could add a simple property to the video sinks to not show the
preroll image for this purpose.

Wim
> 
> 
> ______________________________________________________________________
> De : Tim-Philipp Müller <t.i.m at zen.co.uk>
> À : gstreamer-devel at lists.sourceforge.net
> Envoyé le : Mercredi, 8 Avril 2009, 14h26mn 41s
> Objet : Re: [gst-devel] question on seek
> 
> On Wed, 2009-04-08 at 09:21 +0000, Albert Costa wrote:
> 
> > I have a simple question: I have an application where I want to
> > display only a subset of a video. My pipeline can be resumed to
> > 'filesrc ! decodebin ! ffmegcolorspace ! queue ! directdrawsink'. To
> > see only a part of the video, I use following :
> > 
> >              (snip flushing segment seek)
> >              gst_element_set_state(m_pipeline, GST_STATE_PLAYING);
> >              gst_element_get_state(m_pipeline, NULL, NULL, -1);
> >              gst_element_send_event(m_pipeline, seek_event);
> >
> > where start/stop_time are values for the start and end positions in
> my
> > file.
> > Everything works fine, except for the fact that just before
> displaying
> > the video at position start (and then playing up to stop position),
> I
> > do see the first (0) frame of the video.
> 
> The problem is that the video sink will render the first frame already
> on preroll, so just as it goes into PAUSED state. You are waiting for
> the pipeline to finish prerolling though (and reach playing state on
> top
> of that) before you issue the flushing seek, so at that point it's too
> late and the first frame has already been shown.
> 
> So if you want to avoid that you either have to prevent the videosink
> from drawing preroll buffers, or do the seek before it reaches the
> sink
> (but after you know the demuxer is read for seeking, which is tricky).
> You could probably do something involving pad blocks here. Or use
> gnonlin, as has already been suggested.
> 
> Cheers
> -Tim
> 
> 
> 
> 
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