Why can I stream h264 encoded video from webcam to BOTH display and file, but NOT raw video?

[Hjalmar Turesson]

Hi,

My problem got kind of solved.
It works when I replace x264enc with either theoraenc or vp8enc and
removing h264parse.

Best regards,
Hjalmar

On Wed, Mar 25, 2015 at 9:06 AM, Hjalmar Turesson <hturesson at gmail.com>
wrote:

> Hi,
>
> I want to stream raw video from a Logitech C920 webcam and while *both*
> displaying and saving the video to file using GStreamer 1.0.
>
> This works if I stream h264 encoded video from the camera (the camera
> provides hardware encoded h264), but it fails if I stream raw video from
> the camera. However, if I only display, or only save to file, streaming raw
> video works.
>
> Why does it work with a h264 video stream but not with a raw video stream?
>
> h264 encoded video stream from camera to BOTH display and file (WORKS):
>
> gst-launch-1.0 -v v4l2src device=/dev/video0 ! \
>  video/x-h264,width=640,height=480,framerate=15/1 ! \
>  tee name=t t. ! queue ! h264parse ! avdec_h264 ! \
>  xvimagesink sync=false t. ! queue ! h264parse ! \
>  matroskamux ! filesink location='h264_dual.mkv' sync=false
>
> raw video stream from camera to ONLY display (WORKS):
> gst-launch-1.0 -v v4l2src device=/dev/video0 ! \
>  video/x-raw,format=YUY2,width=640,height=480,framerate=15/1 ! \
>  xvimagesink sync=false
>
> raw video stream from camera to ONLY file (WORKS):
> gst-launch-1.0 -v v4l2src device=/dev/video0 ! \
>  video/x-raw,format=YUY2,width=640,height=480,framerate=15/1 ! \
>  videoconvert ! x264enc ! matroskamux ! \
>  filesink location='raw_single.mkv' sync=false
>
> raw video stream from camera to BOTH display and file (FAILS):
> gst-launch-1.0 -v v4l2src device=/dev/video0 ! \
>  video/x-raw,format=YUY2,width=640,height=480,framerate=15/1 ! \
>  tee name=t t. ! queue ! xvimagesink sync=false t. ! \
>  queue ! videoconvert ! x264enc ! h264parse ! matroskamux ! \
>  filesink location='raw_dual.mkv' sync=false
>
> The last command (raw video to both display and file) fails without any
> warnings or errors. The gst-launch terminal output is exactly the same as
> when only writing to file. The xvimage window appears and displays an image
> from the camera, but the image does not change (i.e. it is frozen). A zero
> bytes file ('raw_dual.mkv') appears too. I tried first using the Python
> bindings and debug threshold set to 4, but only once or twice (randomly)
> did I see something that could be an error message (pausing after
> gst_pad_push() = unknown).
>
> Does anyone understand what I am doing wrong, or what I should do to
> figure out what is wrong?
>
>
> Best regards,
>
> Hjalmar
>
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