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Extract 1 Video Channel from H.264 encoded multi-stream Matroska File

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Class, Phil

Extract 1 Video Channel from H.264 encoded multi-stream Matroska File

Hi,

On Linux, I am able to mux the streams from 2 different V4L2 webcams into a Matroska container with the following pipeline:

gst-launch-1.0 -v -e \
    v4l2src device=/dev/video2 io-mode=4 \
   ! 'video/x-raw, format=(string)UYVY, width=(int)160, height=(int)120' \
   ! videoconvert \
   ! 'video/x-raw, format=(string)NV12, width=(int)160, height=(int)120' \
   ! ducatih264enc \
   ! queue \
        ! "video/x-h264,width=160,height=120" \
   ! h264parse \
   ! queue \
   ! mux. \
    v4l2src device=/dev/video1 \
        ! queue max-size-buffers=0 max-size-time=0 max-size-bytes=0 \
        ! 'video/x-raw, format=(string)YUY2, width=(int)640, height=(int)480, framerate=30/1' \
   ! videoconvert \
   ! 'video/x-raw, format=(string)NV12, width=(int)640, height=(int)480' \
   ! ducatih264enc \
   ! queue \
        ! "video/x-h264,width=640,height=480" \
   ! h264parse \
   ! queue \
        ! mux. \
    matroskamux name=mux min-index-interval=1000000000 \
        ! queue max-size-buffers=0 max-size-time=0 max-size-bytes=0 \
        ! filesink location=test-video.mkv

Now I want to be able to exract one of those video streams like shown in: https://gstreamer.freedesktop.org/documentation/tutorials/basic/gstreamer-tools.html

Basic tutorial 10: GStreamer tools

gstreamer.freedesktop.org

Basic tutorial 10: GStreamer tools Goal. GStreamer comes with a set of tools which range from handy to absolutely essential. There is no code in this tutorial, just sit back and relax, and we will teach you:

I am trying to use the pipeline:

gst-launch-1.0 filesrc location=test-video.mkv ! matroskademux name=d d.video_00 ! queue ! video/x-h264 ! queue ! h264parse ! ducatih264dec ! waylandsink sync=false

The problem is that all variations of this that I try give a "Delayed linking failed" error - here is an example:

Setting pipeline to PAUSED ...[68219.713998] omap-iommu 55082000.mmu: 55082000.mmu: version 2.1
Pipeline is PREROLLING ...
WARNING: from element /GstPipeline:pipeline0/GstMatroskaDemux:d: Delayed linking failed.
Additional debug info:
../../../gstreamer-1.12.2/gst/parse/grammar.y(510): gst_parse_no_more_pads (): /GstPipeline:pipeline0/GstMatroskaDemux:d:
failed delayed linking pad video_00 of GstMatroskaDemux named d to some pad of GstQueue named queue0
ERROR: from element /GstPipeline:pipeline0/GstMatroskaDemux:d: Internal data stream error.
Additional debug info:
../../../gst-plugins-good-1.12.2/gst/matroska/matroska-demux.c(4799): gst_matroska_demux_loop (): /GstPipeline:pipeline0/GstMatroskaDemux:d:
streaming stopped, reason not-linked (-1)
ERROR: pipeline doesn't want to preroll.
Setting pipeline to NULL ...
Freeing pipeline ...

How can I extract one video stream from the matroska file? Thanks.

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Tim Müller

Re: Extract 1 Video Channel from H.264 encoded multi-stream Matroska File

On Fri, 2018-10-05 at 12:45 +0000, Class, Phil wrote:

Hi Phil,

> I am trying to use the pipeline:
>
> gst-launch-1.0 filesrc location=test-video.mkv ! matroskademux name=d
> d.video_00 ! queue ! video/x-h264 ! queue ! h264parse ! ducatih264dec
> ! waylandsink sync=false
>
> The problem is that all variations of this that I try give a "Delayed
> linking failed" error

Try using d.video_0 and d.video_1 instead of d.video_00.

The exact name varies a bit from demuxer to demuxer, but gst-inspect-
1.0 matroskademux shows that the pad template name is "video_%u" rather
than "video_%02u" so I would expect the video pad to be named "video_0"
etc.

Cheers
-Tim

--
Tim Müller, Centricular Ltd - http://www.centricular.com

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