[ivtv-users] cx18 performance

[Al McIntosh]

On Wed, Nov 19, 2008 at 7:35 AM, Andy Walls <awalls at radix.net> wrote:

> On Wed, 2008-11-19 at 01:45 -0500, Al McIntosh wrote:
> > I am recording from the SVIDEO input.
> >
> > On Wed, Nov 19, 2008 at 1:41 AM, Al McIntosh <al at allanmcintosh.com>
> > wrote:
> >         I have been testing the HVR 1600 mostly using mythtv,
> >
> >         1 recording had hyperfast audio playback and I am also
> >         noticing intermittent skips in audio, silence for about a 1
> >         second.
> >
> >         Is this currently common behaviour?
>
> This is a known problem with the first analog (e.g. SVIDEO) capture
> after modprobe.  All subsequent captures after that one should be fine.
>
> I have an idea on how I might fix it.  It's on my todo list.  Since it
> has a simple workaround, it's pretty low on the list.
>
>
>
> >         I noticed this in my dmesg :
> >
> >         [ 3087.476431] cx18-0: Cannot find buffer 33 for stream
> >         encoder MPEG
> >         [ 3087.476442] cx18-0: Could not find buf 33 for stream
> >         encoder MPEG
>
>
> This is the first message in a downward spiral of dropping buffers out
> of the driver <-> firmware buffer transfer rotation.  If enough of those
> happen during a capture, the capture will stall.  It is caused by a long
> interrupt response latency in your system (with the driver contributing
> to that latency). and the driver not checking for the firmware to driver
> mailbox being stale and possibly overwritten by the firmware.
>
> My latest changes in my experimental repo addresses precisely this
> problem.  See my recent announcement on the lists.
>
>
> Regards,
> Andy
>
>


Andy, I'll install and test your dev bundle tonight after work.
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