Re: [gst-devel] videorate for encoded video

[Alexandru C. <oz...@gm...>]

On Wed, Sep 8, 2010 at 10:22 AM, Farkas Levente <lf...@lf...> wrote:
> hi,
> we'd like to make snapshots of an input encoded video stream.
> does anybody have any tip how can we do this?
> unfortunately videorate can only accept raw streams.
> so suppose we've got a h264 input source and like to save the stream and
> every 5 minutes a jpeg image, then this pipeline almost good:
> ---------------------------
> gst-launch -e rtspsrc
> location="rtsp://a-h264-url" ! rtph264depay access-unit=true ! h264parse
> ! tee name="t" ! queue ! matroskamux ! filesink location="test.mkv"  t.
> ! queue ! ffdec_h264 ! videorate !
> video/x-raw-yuv,framerate=1/300 !
> ffmpegcolorspace ! jpegenc ! multifilesink location="frame%05d.jpg"
> ---------------------------
> but in this case we've to decode _all_ frames. and we'd like to save cpu
> and only decode the required frames.
> does anybody has any tips?

Hi Levente,

I don't think you can do that because h264 (and most other video
codecs) rely heavily on inter frame compression. I guess one could do
what you ask by only decoding the key frames, but that would probably
require writing your own decoder.

Alex