v4l2src support for multi channel video capture cards

[anno domini]

Hi Nicolas,

Thanks for responding!
The cards come with Zoneminder and no documentation as to how they operate.
I guess it looks more like the driver is responsible for this ability to
query the channels which would explain why gstreamer cant do it.

Cheers




On Fri, Mar 6, 2015 at 3:59 PM, Nicolas Dufresne <
nicolas.dufresne at collabora.com> wrote:

>
> Le 2015-03-06 10:30, anno domini a écrit :
>
>  We have been using various video capture cards running under linux
>> (Fedora) for quite a while now with gstreamer and it has been very
>> successful - so thanks!
>> We used the older Kodicom type BT878 cards with 8 separate video inputs,
>> each with its own dedicated chip. These are now no longer in production but
>> have been replaced by cards that claim to support up either 4,8 or 16 video
>> inputs. We have tried these out but it appears that they only have 4
>> dedicated chips and only show up as 4 individual video devices i.e.
>>
>> /dev/video0
>> /dev/video1
>> /dev/video2
>> /dev/video3.
>>
>> It looks like there is a concept of channels with these cards whereby
>> each video device can in fact support 4 logically independent inputs.
>> Software like zoneminder and i think possibly VLC and ffmpeg can support
>> these channels but from what i can see gstreamer does not.
>>
>> Can anyone confirm if gstreamer can support these cards.
>> If it doesn't are there any plan to do so.
>> Lastly can anyone suggest a way in which we could hook gstreamer into the
>> channels by some other means?
>>
> Do you have links to documentation on how these "channels" works. Do you
> have links to the driver source code ? V4L2 output device are not supposed
> to be multi-instance by V4L2 SPEC. Did you expect to use 4 instances per
> device nodes ? Note that v4l2sink has been rare, hence it is likely that
> some options are only available through extra-controls property, or by
> opening and configuring the device yourself. Gst will then follow what has
> been configured.
>
> Gst should support valid V4L2 Output device (by valid I mean drivers that
> pass (or at least mostly pass) the v4l2-compliance test). Can you verify
> that ? If it does, and it fails in GStreamer, this is a bug. Bugs should be
> filed with as much details as you can provide in bugs.gnome.org. Always
> specify the version you are using. For V4L2, trace with GST_DEBUG="v4l2*:7"
> are usually appropriate. Attach these as files, not in the comment please.
>
> Nicolas
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