[mythtv] DVB Stability problems with watching live TV

Torbjörn Jansson torbjorn.jansson at mbox200.swipnet.se
Sun Aug 15 10:33:39 EDT 2004

mythtv-dev-bounces at mythtv.org <> wrote:
> On Tue, Aug 10, 2004 at 09:41:27AM +0100, Mark Howells wrote:
>>> This may well be an audio issue. Seems that the alsa/oss sometimes
>>> gets upset when trying to close and reopen the device.
>> Hmmmm, not sure how this could cause the backend to report
> Continuity Errors which is definitely what I see.  Switching
> from LiveTV and then back to the same (faulty) channel fixes
> the continuity errors.
> My theory is that some I/O or CPU overload causes the fifos in the DVB
> card to overflow, and then you get non-stop TS errors due to data
> corruption. But I could never prove it...
> It definitely seemed that a channel change could cause audio problems
> which could cause TS errors. Other times a real TS error could cause
> non-stop TS errors too - but only with MythTV. I never saw it
> happen in
> Xine, which is another reason why I suspect the TS errors aren't real.
> Hamish

I don't know if this is related or not, but i have examined the hdtv and dvb
recorder classes.
The hdtv recorder has some code to check that the ts packet starts with the
proper sync byte, and if it doesn't it tries to resync the stream.
This is not done for dvb, maybe it's not nessesary or maybe the dvb drivers
guarantee that you will always get a complete ts packet.

But if the stream did get out of sync somehow, you woud probably get lots of
errors, i'm not sure if mythtv woud be able to recover from this.
A simple patch like the one attached shoud be able to tell if the dvb
recorder ever gets out of sync somehow.
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