Problem with avdec_h264

[Nicolas Dufresne]

Le jeudi 27 juin 2019 à 14:43 -0500, joker3139 a écrit :
> Hi all,
> I am using a C920 Logitech webcam together with linux to stream. I want to decode this stream to get a raw stream with avdec_h264, but it is not working.
> I have the now following simplified pipeline:
> gst-launch-1.0 -vvv -e v4l2src device=/dev/video ! queue ! video/x-h264,width=1920,height=1080,framerate=30/1 ! h264parse ! avdec_h264 ! fakesink
> When I execute this pipeline, the following error occurs:
> /GstPipeline:pipeline0/avdec_h264:avdec_h264-0.GstPad:sink: caps = video/x-h264, width=(int)1920, height=(int)1080, framerate=(fraction)30/1, alignment=(string)au, stream-format=(string)byte-stream, pixel-aspect-ratio=(fraction)1/1, colorimetry=(string)2:4:7:1, interlace-mode=(string)progressive, chroma-format=(string)4:2:0, bit-depth-luma=(uint)8, bit-depth-chroma=(uint)8, parsed=(boolean)true, profile=(string)constrained-baseline, level=(string)4 
> /usr/bin/recordvideo.sh: line 6: 21423 Illegal instruction gst-launch-1.0 -vvv -e v4l2src device=$1 ! queue ! video/x-h264,width=1920,height=1080,framerate=30/1 ! h264parse ! avdec_h264 ! fakesink
> Especially this error illegal instruction makes me confused as I do not find anything about it...

Looks like a crash ? Run this inside gdb with full debug packages
installed and share a backtrace ? But before, make sure you use the
latest GStreamer stable release (1.16).

> Has anyone an idea why this stream is not decodable with avdec_264?
> I have the original commands from here http://oz9aec.net/software/gstreamer/using-the-logitech-c920-webcam-with-gstreamer-12
> Thank you already for your help!

With the C920, most users will opt for the v4l2src wrapper called
uvh264src. This element will operate the C920 in a HW specific mode
which give you a two streams, a raw stream for viewing and the encoded
stream. It also allow controlling the profile and bitrate of the
encoding. The H264 is already framed properly, that avoids possible
parsing issues.

> 
> Sent from the GStreamer-devel mailing list archive at Nabble.com.
> _______________________________________________
> gstreamer-devel mailing list
> gstreamer-devel at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel