[gst-devel] Slow down videos

Stefan Kost ensonic at hora-obscura.de
Fri Jun 19 14:50:59 CEST 2009

Maximilan Hoegner schrieb:
> Hi,
> is there some simple gst-launch-pipeline to slow down a video file?
> Something like
> gst-launch-0.10 filesrc location=in.wav ! slowdown ! filesink=out.wav
> I know that I can play a video slower if I send a seek event with rate
> != 1.0. But seeking doesn't seem to work with filesink, and I don't know
> how to seek when using gst-launch, if this is possible. So is there a
> simple pipeline I can use with gst-launch?

The above missed demuxers and decoders. You need to fully transcode it.

gst-launch-0.10 filesrc location=in.wav ! decodebin2 ! waveenc ! filesink=out.wav

but even then I am not sure if it will work as imho its the audiosinks that

Regarding seeking and gst-launch - no way. gst-launch is not meant for this. You
need to write a small app.


> In case there is not:
> Is there another way of seeking that does work with filesink? I also
> tried sync=TRUE for the filesink, which had no effect.
> Perhaps I made some mistake in my program structure. I first set the
> state of the pipeline to playing. Then I do a get_state to wait for the
> state change to complete (otherwise seeking has no effect at all, even
> when not using filesink). Then I call
> gst_element_seek(pipeline, 0.5, GST_FORMAT_TIME, GST_SEEK_FLAG_FLUSH,
> which should set the playback rate to 0.5. After that I run the
> gmainloop. This does indeed work if I do not use filesink, but when I
> use it, the file is not slowed down at all (seeking to another position
> doesn't work either). Anything wrong about that?
> I suspect that the work is already done when the program reaches the
> seek line, because state is set to playing before. Doing it the other
> way round does not work however, the seek event does not get handled then.
> Thank you for your help,
> Maxi
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