On Friday 16 February 2007 19:03, Rich Kadel wrote:
> Hans,
>
> OK. Thanks. Those messages are gone. However, now it's exposing
> something new that wasn't a problem with 0.10.0rc1. I started losing
> a lot of data, and getting another LARGE set of log messages.
>
> I restarted my app, started reading in VBI from 8 tuners (no problem
> there), and then I started reading /dev/video from 3 tuners. In
> about 48 seconds, I started getting many of the following:
>
> Feb 16 09:07:35 server2 kernel: ivtv1: All encoder MPEG stream
> buffers are full. Dropping data.
> Feb 16 09:07:35 server2 kernel: ivtv1: Cause: the application is not
> reading fast enough.
>
> Then 10 seconds later, VBI buffer messages joined the MPEG messages:
>
> Feb 16 09:07:35 server2 kernel: ivtv0: All encoder VBI stream buffers
> are full. Dropping data.
> Feb 16 09:07:35 server2 kernel: ivtv0: Cause: the application is not
> reading fast enough.
Note that these messages are from different cards (ivtv0 and ivtv1)!
> I got about 200,000 lines of these messages between 09:00:48 (local)
> and 09:07:38, and then suddenly they stopped (the log messages
> stopped).
>
> I checked the video from one of the tuners, and I lost about 7
> minutes of video. The captions appear to be synchronized with the
> video, so I think I lost about 7 minutes of captions as well.
>
> Doing a vmstat at this point, the load appears to be the same as it
> was with the previous version of the driver.
>
> So, I'm a little confused, but it looks like IVTV had a buffer
> problem, and then tried to recover, dropping data continuously until
> it finally did recover about 7 minutes later. And in the process, it
> created excessive amounts of log messages.
No, the driver is working just fine. It really seems to be your
application that is not reading (or not reading fast enough) from the
video device. The driver is getting MPEG data from the card, tries to
stuff it into the ringbuffer, but no free buffers are available, so it
issues this warning. The only reason this can happen is if the
application is not reading fast enough to empty the full buffers. The
default buffer settings in 0.10.0 give you about 4 seconds of buffering
(1 MB equals 1 second, roughly). So if the application stalls for more
than 4 seconds you will see this messages.
> It's worth noting that the program from 09:30 to 10:00 recorded the
> full 30 minutes of video just fine.
>
> Maybe this was a one-time glitch. I will continue to monitor it and
> let you know if it happens again. But it's coincidental that it
> happened after you fixed the other VBI problem.
I think it is a coincidence. Given the fact that the messages are from
different cards I suspect you're dealing with an application problem
here. This message has been in the driver for a very long time and I
know of only one case where it was a driver bug that caused it instead
of an application bug, and that was with a very early beta of the
0.10.0 driver.
Regards,
Hans
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