[vlc-devel] [rms at gnu.org: VLC and V4L2]

Richard Hosking richard at hovis.net
Thu Oct 4 10:58:10 CEST 2007

I have more or less completed this.  Only mjpeg support
and testing with a device which has a tuner I cannot do
as my v4l2 device does not support this.

Currently the v4l2 device I have has a bug in its drivers
which crashes when the device is closed. I am waiting for
the manufacturer to fix this fault (hopefully the end of
next week).  When they do this I will be able to test
that the calling code works properly before submitting my
v4l2.c file for hopeful inclusion into the trunk :-)

About 50% of the additions are taken from the reference
v4l2 capture program at http://v4l2spec.bytesex.org/spec/a14009.htm
(which I have cited), and about 30% is from the v4l.c
program, and the rest is me.

I would rather wait until I can verify that the bug I
have is fixed before submitting my v4l2.c patch, but if
anyone wishes to see the current code it is here:-


(line 651 is the call which is causing my device to
segfault at the moment)


Benjamin Pracht wrote:
> I would welcome any comment on this. I guess what we really lack here is
> a developer willing to spend some time on it. Does anybody see anything
> concrete the FSF can do to help? I remember some emails on this mailing
> list about some people working on the v4l2 module. Did we get any feedback?
> Writing a full support for all the v4l2 compatible devices might be a
> rather big work, but even a basic support of some devices would be a
> very nice first step.
> Currently, the v4l2.c file only contains probing code. I'm not even sure
> we really want to keep it. The pvr module probably also have useful
> code for the access part.
> What remains to be done is mostly:
> - to split the module in an access and an access_demux
> - complete the probing code
> - write device selection, device configuration code (source, tuner 
>   properties, v4l chroma to vlc FOURCC currespondance, etc)
> - write the data reading routines (some devices use read calls on the
>   device node, some use ioctls)
> - callbacks usable from a gui to get the device list (see direct show)
> - probably lots of other things I forget. I worked on those more than 1
>   year ago, not exactly sure anymore about how all this works.
> I'm afraid I won't be able to take this over. I can try to help anybody
> having questions on the existing code, but again, it's not much and I
> don't think there is a lot to say about it.
> ------------------------------------------------------------------------
> Subject:
> VLC and V4L2
> From:
> Richard Stallman <rms at gnu.org>
> Date:
> Sat, 29 Sep 2007 23:04:08 -0400
> To:
> bigben at videolan.org
> To:
> bigben at videolan.org
> I would really like VLC to work with V4L2, so I wonder: is there
> anything the FSF could do to help you make progress on this?  Please
> tell me what would be useful.
> ------------------------------------------------------------------------
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