[linux-dvb] Re: dvb(nova) interrupt/dma timing

["Matthias Behr" <mbehr@mcbehr.de>]

Hi,

see my mail to this ml from 28.8.02, 16:28. "bug in dvb.c fidbirq()?"

"I think there is a bug in driver/dvb.c (cvs rev 1.142) in fidbirq(...).
...
This will lead to duplicated packets (which is (most of the time) no problem
if it's just one but ...).
..."

This happens with a nova like card as well. I described a possible bugfix
but nobody replied yet.

Regards,
Matthias

----- Original Message -----
From: "Wolfgang Wegner" <ww@kt.e-technik.uni-dortmund.de>
To: <linux-dvb@linuxtv.org>
Sent: Thursday, August 29, 2002 12:18 PM
Subject: [linux-dvb] dvb(nova) interrupt/dma timing


> Hi all,
>
> i have some questions concerning the dma and interrupt timing (or
> synchronization), especially for the nova card.
> I am trying to do some stream parsing using a function hooked up at
> the beginning of DvbDmxSWFilterPackets in dvb_demux.c.
> My problem is that _sometimes_ i get "wrong" data, which seems to be
> due to old data being read from the buffer. I can in fact change the
> behaviour towards better by including some printk's (and thus slowing
> down) in my code.
> The data read from /dev/ost/dvr is apparently always correct, at least
> the "stream error detector" vlc does not crash, however, i can not
> see any wrong data in my code's output either while running vlc...
>
> Again, normally everything works as expected, only sometimes it seems
> that there is old data read, especially towards the end of the buffer,
> this is why i am thinking of such a timing problem. (I am only scanning
> PIDs and PCRs, not the whole packets, so - at least i hope - my code is
> quite fast.)
>
> This happens on both an 800 MHz PIII and a 1470MHz Athlon, i could not
> clearly state it is more common on one of them.
>
> Is the behaviour of DMA and interrupts being slightly "out of sync" i
> am suspecting here possible at all? If so, is there anything i can do
> about it (like querying a DMA address pointer etc.)? I have to admit i
> do not really understand how debiirq and stuff works... :(
>
> Any hints are appreciated. :)
>
> Thanks,
> Wolfgang
>
>
>
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