[gstreamer-bugs] [Bug 578500] New: v4l2src caps

[GStreamer (bugzilla.gnome.org)]

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  GStreamer | gst-plugins-good | Ver: 0.10.21
           Summary: v4l2src caps
           Product: GStreamer
           Version: 0.10.21
          Platform: Other
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: gst-plugins-good
        AssignedTo: gstreamer-bugs at lists.sourceforge.net
        ReportedBy: francois.forest at lri.fr
         QAContact: gstreamer-bugs at lists.sourceforge.net
     GNOME version: Unspecified
   GNOME milestone: Unspecified


The pipeline
    v4l2 --> ffmpeg --> filter rgb --> xsink
triggers "could not negotiate" at v4l2 level.
If xsink is defined as ximagesink rather than xvimagesink, the test works.

a third test with an additionnal filter forcing yuv in v4l2 is nok.

3 tests are reported below using gst-launch, the same is observed building the
pipelines in Python.

Note: v4l2src publishes caps x-raw-rgb while my webcam is only able to
generate x-raw-yuv or MPEG. This may be linked to the problem.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
    ProblemA/test1 -  works as expected
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
$ gst-launch-0.10  v4l2src ! ffmpegcolorspace ! video/x-raw-rgb ! ximagesink

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
    ProblemA/test2 -  ximagesink is replaced by  xvimagesink (has more caps)
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
$ gst-launch-0.10  v4l2src ! ffmpegcolorspace ! video/x-raw-rgb ! xvimagesink
ERROR: Pipeline doesn't want to pause.
ERROR: from element /GstPipeline:pipeline0/GstV4l2Src:v4l2src0: Could not
negotiate format
Additional debug info:
gstbasesrc.c(2426): gst_base_src_start ():
/GstPipeline:pipeline0/GstV4l2Src:v4l2src0:
        ...

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
    ProblemA/test3 - force YUV in v4l2src
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
$ gst-launch-0.10 v4l2src !  video/x-raw-yuv,width=320,height=240 !
ffmpegcolorspace ! video/x-raw-rgb,width=320,height=240 ! xvimagesink

ERROR: Pipeline doesn't want to pause.
ERROR: from element /GstPipeline:pipeline0/GstV4l2Src:v4l2src0: Could not
negotiate format
Additional debug info:
gstbasesrc.c(2426): gst_base_src_start ():
/GstPipeline:pipeline0/GstV4l2Src:v4l2src0:


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