[gst-devel] Grabbing snapshots out of live stream

[OB Lutz]

I've managed to get passed the whole single-frame issue, but am getting
pipeline errors when actually running it using something closer to my final
pipeline.

I've reduced my problem to the following command. This is taking in raw YUY2
data(eventually to be replaced by some sort of mjpeg stream, but I have
access to YUY2 currently), shoving it in a tee and writing out frames to a
file.

gst-launch -vvv gstrtpbin name=rtpbin \
              tcpserversrc host=127.0.0.1 port=1235 ! videoparse format=YUY2
width=404 height=424 framerate=20/1 bpp=16 ! \
              tee name=splitter splitter.  ! queue ! typefind ! pngenc
snapshot=false ! multifilesink sync=false preroll-queue-len=20
location=/tmp/output.png -vvv splitter.

This starts up fine, with:

Setting pipeline to PAUSED ...
Pipeline is PREROLLING ...

 but when I start sending data to it, I error out with:

/pipeline0/videoparse0.src: caps = video/x-raw-yuv, width=(int)404,
height=(int)424, format=(fourcc)YUY2, framerate=(fraction)20/1,
pixel_aspect_ratio=(fraction)1/1
/pipeline0/splitter.sink: caps = video/x-raw-yuv, width=(int)404,
height=(int)424, format=(fourcc)YUY2, framerate=(fraction)20/1,
pixel_aspect_ratio=(fraction)1/1
/pipeline0/splitter.src0: caps = video/x-raw-yuv, width=(int)404,
height=(int)424, format=(fourcc)YUY2, framerate=(fraction)20/1,
pixel_aspect_ratio=(fraction)1/1
/pipeline0/splitter.sink: caps = video/x-raw-yuv, width=(int)404,
height=(int)424, format=(fourcc)YUY2, framerate=(fraction)20/1,
pixel_aspect_ratio=(fraction)1/1
/pipeline0/queue0.sink: caps = video/x-raw-yuv, width=(int)404,
height=(int)424, format=(fourcc)YUY2, framerate=(fraction)20/1,
pixel_aspect_ratio=(fraction)1/1
/pipeline0/queue0.src: caps = video/x-raw-yuv, width=(int)404,
height=(int)424, format=(fourcc)YUY2, framerate=(fraction)20/1,
pixel_aspect_ratio=(fraction)1/1
/pipeline0/typefindelement0.src: caps = video/x-raw-yuv, width=(int)404,
height=(int)424, format=(fourcc)YUY2, framerate=(fraction)20/1,
pixel_aspect_ratio=(fraction)1/1
/pipeline0/typefindelement0.sink: caps = video/x-raw-yuv, width=(int)404,
height=(int)424, format=(fourcc)YUY2, framerate=(fraction)20/1,
pixel_aspect_ratio=(fraction)1/1
ERROR: from element /pipeline0/tcpserversrc0: Internal data flow error.
Additional debug info:
gstbasesrc.c(2193): gst_base_src_loop (): /pipeline0/tcpserversrc0:
streaming task paused, reason not-negotiated (-4)
ERROR: pipeline doesn't want to preroll.
Setting pipeline to NULL ...
/pipeline0/typefindelement0.src: caps = NULL
/pipeline0/typefindelement0.sink: caps = NULL
/pipeline0/queue0.src: caps = NULL
/pipeline0/queue0.sink: caps = NULL
/pipeline0/splitter.src0: caps = NULL
/pipeline0/splitter.sink: caps = NULL
/pipeline0/videoparse0.src: caps = NULL
FREEING pipeline ...

Once this works, there will be another queue off of the 'splitter' tee that
goes through some processing before heading out to a gsrtpbin/udpsink (hence
the part about a gstpbin at the start of the pipeline. removing that part
yeilds the same results).

Thanks
-Brian

On Mon, Jan 12, 2009 at 10:33 AM, Arnout Vandecappelle <arnout at mind.be>wrote:

> On Thursday 08 January 2009 22:48:04 OB Lutz wrote:
> > I'm trying to write a pipeline that will take video in from a network
> > source, do some transcoding, and send it out to a network sink. No
> problem
> > there. But I need to be able to get preview snapshots of the stream as
> its
> > running, either on demand, or just have it continuously dump out frames
> to
> > a known file periodically. I'm doing some experiments using a v4lsrc and
> > xvimagesink as my fake network source and sink for now. I've found the
> > 'tee' block that looks promising to split my stream into 2, so one can go
> > on its way to the network sink, and the other could maybe write to a
> file,
> > but all my experiments have only shown me a single frame in my
> xvimagesink.
> > Am I going down the right path trying to use 'tee' or is there some other
> > set of blocks I should use?
>
>  You probably need to insert a queue behind the tee.  Otherwise you can get
> deadlocks because all sinks try to synchronize from the same thread.
>
>  Failing that, can you post the gst-launch command you're using?
>
>  Regards,
>  Arnout
>
> --
> Arnout Vandecappelle                               arnout at mind be
> Senior Embedded Software Architect                 +32-16-286540
> Essensium/Mind                                     http://www.mind.be
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