[Ffmpeg-devel] [Fwd: A question about v4l2 interface for ffmpeg]

[Luca Abeni]

Hi all,

I received this email about a problem with v4l2 input.
The problem seems to be that compressed video input is not supported
(and the reporter's video grabbing card does not support uncompressed
video).

I currently have no time to implement support for compressed video in
v4l2.c, but maybe someone else might want to have a look at it.


			Thanks,
				Luca

-------- Forwarded Message --------
> From: Leopold Palomo-Avellaneda <lepalom at wol.es>
> To: lucabe72 at email.it
> Subject: A question about v4l2 interface for ffmpeg
> Date: Fri, 20 Oct 2006 12:19:43 +0200
> Dear Luca,
> 
> I wrote you directly as the last author of the v4l2 interface form the ffmpeg 
> suite. I'm trying to use the v4l2 interface to a device that give a 
> compressed stream in mpg2 o mpg4 o mjpeg. You can override the default 
> parameters of the device.
> 
> I'm trying to open the device with the ffmpeg suite. Using a simple example 
> from [1] with the libavformat I have this error when I try to open it:
> 
> ./avcodec_sample /dev/video1
> [video4linux2 @ 0xa7f4a610][3]Capabilities: 4000001
> [video4linux2 @ 0xa7f4a610]Cannot find a proper format.
> Segmentation fault
> 
> looking on gdb:
> 
> [New Thread -1486502208 (LWP 7823)]
> [video4linux2 @ 0xa7f61610][7]Capabilities: 4000001
> [video4linux2 @ 0xa7f61610]Cannot find a proper format.
> 
> Program received signal SIGSEGV, Segmentation fault.
> [Switching to Thread -1486502208 (LWP 7823)]
> 0xa7ef4ed2 in av_find_stream_info () from /usr/lib/libavformat.so.0d
> (gdb) bt
> #0  0xa7ef4ed2 in av_find_stream_info () from /usr/lib/libavformat.so.0d
> #1  0x08048ca1 in main ()
> 
> 
> the code that use this is:
> 
> .....
>     AVFormatParameters formatParams;
>     AVInputFormat *iformat;
> 
>     formatParams.device = argv[1];
>     formatParams.channel = 0;
>     formatParams.standard = "pal";
>     formatParams.width = 768;
>     formatParams.height = 576;
>     iformat = av_find_input_format("video4linux2");
> 
>     av_open_input_file(&pFormatCtx, "", iformat, 0, &formatParams);
> .....
> 
> 
> my question if I'm trying to do something impossible, because it's not 
> implemented or I'm doing it wrong?
> 
> Or, there are some other way to send a stream th the libavcodec from a v4l2 
> device?
> 
> Regards,
> 
> Leo
> 
> 
> [1] http://www.inb.uni-luebeck.de/~boehme/libavcodec_update.html