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

Rafaël Carré funman at videolan.org
Thu Oct 4 13:50:00 CEST 2007

Hash: SHA1

Richard Hosking a écrit :
> 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.

Maybe the FSF can help here, providing you such a device ?
I have no idea how much it costs.

> 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.

The reference capture program is 404 for me, is it in the public domain,
or has a special licence ?

> 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:-
> http://hovis.net/v4l2.c
> (line 651 is the call which is causing my device to
> segfault at the moment)

Seems odd, did you verify you were not overflowing ?

> Richard.


> 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.

- --
Rafaël Carré
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