v4l2src and a usb tv tuner

[Stefan Kost]

On 28.02.2011 00:41, Dimitar Popov wrote:
> Hi all,
>
> I'm having problem using my usb tv tuner with gstreamer. I tried the following 
> with gst-launch-0.10:
>
> $ gst-launch-0.10 v4l2src device=/dev/video1 ! autovideosink
>
> Setting pipeline to PAUSED ...
> ERROR: Pipeline doesn't want to pause.
> ERROR: from element /GstPipeline:pipeline0/GstV4l2Src:v4l2src0: Device 
> '/dev/video1' cannot capture at 720x576
> Additional debug info:
> gstv4l2object.c(2093): gst_v4l2_object_set_format (): 
> /GstPipeline:pipeline0/GstV4l2Src:v4l2src0:
> Call to S_FMT failed for YV12 @ 720x576: Invalid argument
> Setting pipeline to NULL ...
> Freeing pipeline ...
>
> Then I checked what properties v4l2 reports:
>
> $ v4l2-ctl -d /dev/video1 --all
>
> and noticed that the tv tuner uses YUY2 (also known as YUYV) instead of YV12 
> as detected by GST:
>
> Format Video Capture:
>         Width/Height  : 720/576
>         Pixel Format  : 'YUYV'
>         Field         : Interlaced
>         Bytes per Line: 1440
>         Size Image    : 829440
>         Colorspace    : SRGB
> Format Video Output:
>         Width/Height  : 720/576
>         Pixel Format  : 'YUYV'
>         Field         : Interlaced
>         Bytes per Line: 1440
>         Size Image    : 829440
>         Colorspace    : SRGB
>
> So I decided to explicitly tell GST to use YUY2:
>
> gst-launch-0.10  v4l2src device=/dev/video1 ! video/x-raw-
> yuv,format=\(fourcc\)YUY2 ! ffmpegcolorspace ! autovideosink
>
> but got:
>
> Setting pipeline to PAUSED ...
> ERROR: Pipeline doesn't want to pause.
> ERROR: from element /GstPipeline:pipeline0/GstV4l2Src:v4l2src0: Could not 
> negotiate format
> Additional debug info:
> gstbasesrc.c(2778): gst_base_src_start (): 
> /GstPipeline:pipeline0/GstV4l2Src:v4l2src0:
> Check your filtered caps, if any
> Setting pipeline to NULL ...
> Freeing pipeline ...
>
> Adding --gst-debug=v4l2:5 revealed that GST recognises YU12, YV12, BGR3 and 
> RGB3 pixel formats:
>
> v4l2 gstv4l2object.c:1038:gst_v4l2_object_fill_format_list:<v4l2src0>   YU12 
> (emulated)
> v4l2 gstv4l2object.c:1038:gst_v4l2_object_fill_format_list:<v4l2src0>   YV12 
> (emulated)
> v4l2 gstv4l2object.c:1038:gst_v4l2_object_fill_format_list:<v4l2src0>   BGR3 
> (emulated)
> v4l2 gstv4l2object.c:1038:gst_v4l2_object_fill_format_list:<v4l2src0>   RGB3 
> (emulated)
>
> The version of gstreamer is 0.10.32 and the version of gst-plugins-good is 
> 0.10.27 from the archlinux x86_64 repo.
>
> I've attached the debug output from gst-launch and the output of v4l2-ctl, but 
> if any other information is needed I'll provided of course.

Current git has a fix for interlaced v4l2 sources which could fix your
problem.

Stefan
> I'm not an expert in the field so I have only a vague notion of what 
> colorspace and pixel formats are, so please, execuse me, if I've done some 
> stupid mistake :)
>
> Thanks in advance for the help!
>
> Dimitar
>
>
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