[linux-dvb] Re: Continuity Errors with tda10021 (Re: Distorded video with Cinergy1200 DVB-C)

Markus Schulz msc at antzsystem.de
Fri Feb 18 02:39:43 CET 2005


Am Mittwoch, 16. Februar 2005 16:32 schrieb slickhenry:
> Robert Schlabbach:
> > Is it possible that the "distortions" you are seeing are _not_ the
> > result of reception errors, but rather the result of incorrect DMA
> > transfers from the SAA7146A to the PCI bus? If you have no issues
> > with QAM64 channels, that might only be due to their lower data
> > rate.
>
> All my channels are QAM64.

same here

> I've gotten around to play with dvbsnoop. And indeed,
> Transport_error_indicator remains 0 all the time, while the
> continuity counters seem to indicate lots of lost ts-packets for the
> garbled channels.

i have the same problem with same card.(but significant less packet loss 
rate, ~150 packets during a 90 minutes movie)

> Is there any way of rectifying this or reasearch where they are lost?

The packets are lost in dvb_dmx_swfilter_packets cause of sync byte 
(0x47) can't be found at next "Modulo 188" address and so the whole 
packet (next 188 bytes) are skipped. 
i've build some debug code to search from this position for sync byte 
and in my case the missing sync byte was everytime one byte behind 
original position and the packet from this position one byte to small 
(after 187 bytes the next sync byte is found).

Like Robert say'd i think too that errors come from (timing) problem 
while writing via dma into memory. But i don't familiar with saa7146 
programming to fix it.

here you can read my previous results:
http://thread.gmane.org/gmane.linux.drivers.dvb/13431

what hardware are you using?
i'm using an asus a7v333 (via kt333 chipset) amd system.

-- 
Markus Schulz




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