bttv driver problem last kernels

bttv driver problem last kernels

[Linos]

Hello all,
	i am using a bttv multicapture board and i have been having increasing problems in last kernels, i am using 
two programs to capture my video input for security reasons (helix producer and mp4live from mpeg4ip project) 
since the first versions of v4l2 in 2.4 patched kernel versions i can attach the two programs at the same time 
at the same video input, only loss framerate but i am using a low framerate to transmit by internet anyway, 
before 2.6.22 all have worked very well (i have not tested 2.6.21, the last kernel working ok i have tested is 
2.6.20) but after that bttv driver is getting worse and worse, from 2.6.22 to 2.6.24 i get this if i try to 
launch the second process in the same video input:

first mp4live works ok when i launch producer: Error: Could not set image size to 352x288 for color format 
I420 (15) (VIDIOCMCAPTURE: buffer 0)
first producer works ok when i launch mp4live: 12:59:59.333-mp4live: Failed to allocate video capture buffer 
for /dev/video0

and in 2.6.25 worse yet it has a deadlock, i have applied the patch listed here 
http://lkml.org/lkml/2008/5/17/139 but still doesnt works for capturing anything, before the patch it hangs 
the process after the patch it gives me other error about buffers different from the above in the first 
process attached to the video input so it is unusable.

Obviously my problem here it is that if i want to upgrade hardware i can have problems with sata, chipsets, 
audio or any other new hardware no supported in older kernels (apart from missing features). Should the 
situation with bttv drivers be better in future kernels or it is letting die for better support for new chips?

Regards,
Miguel Angel.

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Re: bttv driver problem last kernels

[Daniel Glöckner]

On Fri, Jun 06, 2008 at 01:34:17PM +0200, Linos wrote:
> Hello all,
> 	i am using a bttv multicapture board and i have been having 
> 	increasing problems in last kernels, i am using two programs to capture my 
> video input for security reasons (helix producer and mp4live from mpeg4ip 
> project) since the first versions of v4l2 in 2.4 patched kernel versions i 
> can attach the two programs at the same time at the same video input, only 
> loss framerate

You are relying on undocumented behaviour when two v4l1 applications are
reading from bttv at the same time. Furthermore the v4l2 standards says

"1.1.4. Shared Data Streams

V4L2 drivers should not support multiple applications reading or writing
the same data stream on a device by copying buffers, time multiplexing
or similar means. This is better handled by a proxy application in user
space. When the driver supports stream sharing anyway it must be
implemented transparently. The V4L2 API does not specify how conflicts
are solved."

You should change your setup to use only one application accessing the
device.

  Daniel

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Re: bttv driver problem last kernels

[Linos]

Daniel Glöckner escribió:
> On Fri, Jun 06, 2008 at 01:34:17PM +0200, Linos wrote:
>> Hello all,
>> 	i am using a bttv multicapture board and i have been having 
>> 	increasing problems in last kernels, i am using two programs to capture my 
>> video input for security reasons (helix producer and mp4live from mpeg4ip 
>> project) since the first versions of v4l2 in 2.4 patched kernel versions i 
>> can attach the two programs at the same time at the same video input, only 
>> loss framerate
> 
> You are relying on undocumented behaviour when two v4l1 applications are
> reading from bttv at the same time. Furthermore the v4l2 standards says
> 
> "1.1.4. Shared Data Streams
> 
> V4L2 drivers should not support multiple applications reading or writing
> the same data stream on a device by copying buffers, time multiplexing
> or similar means. This is better handled by a proxy application in user
> space. When the driver supports stream sharing anyway it must be
> implemented transparently. The V4L2 API does not specify how conflicts
> are solved."
> 
> You should change your setup to use only one application accessing the
> device.
> 
>   Daniel
> 

I have two options here:

1) maintain 2.6.20 kernel version
2) search for an application proxy that lets me use the same input for two programs

i have a windows client connecting the two streams in different options, i cant disable any of them and i cant 
double the number of capture inputs in the system, anyway i have not read the v4l2 standard so you have reason 
that i should not be doing that but i have been doing from 2.4.17 (with patches) to 2.6.20.

Regards,
Miguel Angel.

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