[linux-dvb] A/V sync issues with DVB-S

Thomas Börkel thomas at boerkel.de
Wed Aug 20 06:52:25 CEST 2008


hermann pitton wrote:

Thanks for the informations.

>> Is it normal, that every now and then (1-2 of 10 recordings), I get one
>> serious (suddenly 30 frames off) A/V sync problem with DVB-S?

> DVB-C is in general much better protected against troubles generated by
> changing environmental conditions, but in case of weather conditions
> which suddenly create ice on any surface, it is better to know the one
> in charge even there.


> Means, watch your dish. Maybe birds or a cat like to stay there
> sometimes or wind might move branches of a tree in the near of it.

There is no tree, but could be birds.

> This is card/frontend specific, but for the very few I have in critical
> reception conditions, SNR below 50% is a clear indicator that I won't
> have to blame any apps later. A thunderstorm comes up.

Measuring the strength and SNR is not so easy now. My SAT receiver
always says strength 70% and SNR 80%. My new Nova S Plus cards always
report strength 97% and SNR 99%. Only my TT 1500s reported reasonable
numbers like strength 63-80% and SNR 75-90%.

In the end, I think overall strength and SNR is not my problem. I always
get a lock. It's the glitches that happen every now and then.

> After that, on normal mpeg2 DVB-S all applications should still do
> fairly well, but if you go out for x264 HDTV, it is another and
> completely different additional story, especially for what I see on
> x86-64 quad CPUs.

I am not recording x264 at the moment, meaning I have no DVB-S2 card.

Thanks for the informations.


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