Cant take an immediate screenshot image of static video from h264 rtp stream

[anno domini]

Should have pointed out...the udpsink port=8554 should have read as udpsink
port=8555

On Thu, Sep 18, 2014 at 2:34 PM, anno domini <genericgroupmail at gmail.com>
wrote:

> HI All,
>
> Would really appreciate any suggestions for an issue i am experiencing.
> I had been happily taking screenshots from a regular v4l2src linux device
> using gstreamer using the following pipeline (i am using pythons gstreamer
> packages for this):
>
> v4l2src device=/dev/video1 norm=PAL ! ffmpegcolorspace ! valve
> name=video_capture_valve drop=true ! videoscale ! video/x-raw-rgb, bpp=24,
> width=720, height=576, pixel-aspect-ratio=1/1 ! pngenc snapshot=true
> compression-level=1 ! filesink location=/tmp/blah.png
>
> The valve is just so i can control exactly when to take the snapshot. When
> it is opened (i.e. drop=false) the png is generated almost immediately.
>
> However, when I changed the src to be udpsrc receiving h264 RTP video it
> sometimes takes up to 40 seconds after opening the valve before the png is
> created.
> A bit of investigation shows that this only happens when the video content
> is static (e.g. a video of pure black or just motionless content). I'm
> guessing this is because with h264 compression, static video produces very
> little bits and hence it takes longer before the buffers build up enough to
> empty down through the pipeline:
>
> udpsrc port=8555 ! application/x-rtp, payload=96 ! rtph264depay !
> ffdec_h264 ! ffmpegcolorspace ! valve name=video_capture_valve drop=true !
> videoscale ! video/x-raw-rgb, bpp=24, width=720, height=576,
> pixel-aspect-ratio=1/1 ! pngenc snapshot=true compression-level=1 !
> filesink location=/tmp/blah.png
>
> So my question is does anyone have any suggestions as to how i could
> change things to ensure an immediate screenshot/image is taken?
>
> Just for completion, here is the command line pipeline i use to generate
> the RTP source in the first place:
>
> gst-launch -v -e v4l2src device=/dev/video1 norm=PAL ! videoscale !
> video/x-raw-rgb, width=720, height=576, pixel-aspect-ratio=1/1 !
> ffmpegcolorspace ! tee name=videoTee \
> videoTee. ! queue ! x264enc tune="zerolatency" threads=1
> intra-refresh=true ! rtph264pay config-interval=2 ! udpsink port=8554
>
> Thanks!
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.freedesktop.org/archives/gstreamer-devel/attachments/20140918/714fb399/attachment.html>