[Ffmpeg-devel] [Fwd: A question about v4l2 interface for ffmpeg]
Sun Oct 22 18:02:40 CEST 2006
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
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.
-------- 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  with the libavformat I have this error when I try to open it:
> ./avcodec_sample /dev/video1
> [video4linux2 @ 0xa7f4a610]Capabilities: 4000001
> [video4linux2 @ 0xa7f4a610]Cannot find a proper format.
> Segmentation fault
> looking on gdb:
> [New Thread -1486502208 (LWP 7823)]
> [video4linux2 @ 0xa7f61610]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;
> 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
>  http://www.inb.uni-luebeck.de/~boehme/libavcodec_update.html
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