Multithreaded fast-forward possible?

[Juraj Holtak]

Hi,

Maybe worth a try:

Put an "queue" element before and after ffdec_h264 and use
max-threads=<your_cpu_count>. I imagine it worked like this for me but
maybe I just had luck...

Juraj
On Dec 13, 2012 2:03 AM, "Peter Rennert" <p.rennert at cs.ucl.ac.uk> wrote:

> Dear all,
>
> I want to increase the playback of a video quite drastically. At the
> moment I am playing a test video sequence with
>
> gst-launch-0.10 filesrc location=/path/to/my.mp4 ! qtdemux ! h264parse !
> ffdec_h264 name=dec ! ffmpegcolorspace ! deinterlace ! xvimagesink
>
> and at some point the video speed cannot get increased further, because it
> uses only one CPU core to decode the video. Gstreamer starts complaining of
> getting behind the timestamps of the stream and crashes.
>
> I could think of two solutions:
>     - Is there a "native" way of making use of more than just a single
> core to decode the video frames? I tried to set "max-threads" of ffdec_h264
> to 4, but it still only uses a single core.
>
> or,
>     - Is there a way of skipping frames? As I need only a "effective"
> framerate on the screen of about 25fps I could just decode the frames I
> need and skip the other frames. Then I would not need more CPU power than
> for realtime playback.
>
> or.
>     - Is there a way to split the stream after the qtdemux and use several
> decoders in a kind of decoder pool (distribute the frames between them) and
> unify the stream after?
>
> My videos are in H264 format. I am not sure if the non-keyframes are
> encoded with respect to the previous frame or with respect to the last
> key-frame. In that case I could try to filter the key-frames and send them
> to every decoder in the pool and decode the any frame with that as
> reference until the next key-frame. With some management I could try to
> merge the output of the pool decoder with a input-selector. But that sounds
> bulky :\ So if one knows how to get to one of the first two solutions, I
> would be very happy...
>
>
> Cheers,
>
> Peter
>
> PS I am happy to provide an example video. Maybe something is wrong with
> the encoding there that prevents ffdec_h264 to use multiple cores
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