[mythtv] what does "DVBRec(1): PID 0x840 discontinuity detected" mean?

Stuart Auchterlonie stuarta at squashedfrog.net
Fri Sep 29 19:42:01 UTC 2006

On Fri, Sep 29, 2006 at 02:59:03PM -0400, Steven Adeff wrote:
> Starting about 3 weeks ago I've been getting these errors with lots of
> glitches on my ATSC tuners.
> I had the cable guy come out today and he cleaned up some of the noise
> being experienced on the line and said that the signal out of the wall
> is as good as it gets.

okay so the wall signal is pretty good.

> So what I'm wondering is what else could be causing errors like these:
> 2006-09-29 14:47:56.303 DVBRec(1): PID 0x840 discontinuity detected
> 2006-09-29 14:47:56.304 DVBRec(1): PID 0x840 discontinuity detected


These are caused by the next packet being recieved on that pid,
not being the one that is expected.

The main cause is bad signal, but you've had that sorted.
It can also caused by things like power spikes, or other
intermittant interferance.

However, looking at this i've noticed something interesting.
We don't throw away the packet if we detect a discontinuity.
This would be okay if the new packet CC = last seen CC, as this
would possibly be a duplicate packet. But if the new packet CC
is > last seen CC + 1 (modulo 0xf) then the full TS packet is
broken and should be thrown away....

I'll whip up a quick patch for that...


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