[Ffmpeg-devel] Streaming from camera segfaults on Ubuntu Dapper

Luca Abeni lucabe72
Mon Oct 30 12:48:03 CET 2006

Hi Timo,

On Fri, 2006-10-27 at 12:57 +0300, Timo Rantalaiho wrote:
> > The driver is claiming that it is returning a frame of size 460800...
> > Maybe I misunderstood the v4l2 specifications, but this looks wrong to
> > me (if I am not wrong, 460800 should be the buffer size for a 640x480
> > frame).
> It seems to, because when I changed the frame size to 
> 640x480 it was actually able to grab something! Grabbing 
> to mpeg to disk works!
Ok, so it seems that either I or the driver's author misunderstood
something in the video4linux2 specification... I am going to have a
better look at this driver. You are using a Logitech Quickcam 8000,
right? Which driver are you using? (Which kernel version are you using?
What's the driver's name? Is it in upstream kernel, or did you have to
recompile it? In the second case, where can the driver be downloaded
from? )

> However, what I _really_ wanted to do (stream with ffserver) 
> still doesn't work too well. The picture is very flaky and 
> with a lot of delay, and there is a lot of "buffer underfow" 
> output from ffserver:
> buffer underflow.0 size=    1268kB time=82.2 bitrate= 126.4kbits/s
> buffer underflow
> buffer underflow
> buffer underflow
> frame= 2075 q=31.0 Lsize=    1280kB time=83.0 bitrate= 126.4kbits/s
> video:477kB audio:0kB global headers:0kB muxing overhead 168.392719%
I do not know ffserver very much, but I think the problem here is that
the selected bitrate is too low (maybe the bitrate is ok for a 320x280
picture, but 640x480 is too large for this bitrate). Try increasing the

Anyway, I want to make v4l2.c work with your setup... I hope you'll be
able to grab at 320x240 in a short time.

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