[linux-dvb] Corrupted MPEGs (DVB-C)?

Thomas Börkel thomas at boerkel.de
Mon Aug 14 08:30:46 CEST 2006


HI!

Recorded DVB-C mpeg files seem to be somehow corrupted or illegal. I can 
watch them perfectly with mplayer and MythTV, but skipping/jumping 
through them causes problems.

MythTV (using ffmpeg) reports most of the time things like this, but the 
picture is visually OK:
[mpeg2video @ 0xb73fc7e4]skipped MB in I frame at 1 29
[mpeg2video @ 0xb73fc7e4]ac-tex damaged at 0 30

Using mplayer (libmpeg2) causes pixelization for a short moment after 
the skip, but it does not report errors. When I switch MythTV from 
ffmpeg to libmpeg2, it behaves the same (no error messages, but 
pixelization).

Is this "normal"? As I said, it only happens when skipping, not when 
playing.

I am using a KNC One DVB-C card (SAA7146, budget_av driver) in a Suse 
10.1 machine (kernel 2.6.16.21-0.13-smp), DVB drivers were included with 
that kernel.

dvbscan finds all channels and I can tune to all channels with czap with 
this output for example:

using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
reading channels from file 'channels.conf'
149 DAS 
VIERTE:762000000:INVERSION_AUTO:6900000:FEC_NONE:QAM_64:2047:2048:1793
149 DAS VIERTE: f 762000000, s 6900000, i 2, fec 0, qam 3, v 0x7ff, a 0x800
status 1f | signal 9696 | snr eded | ber 00195000 | unc ffffffff | 
FE_HAS_LOCK
status 1f | signal 9393 | snr eeee | ber 00195000 | unc 00000000 | 
FE_HAS_LOCK
status 1f | signal 9393 | snr eded | ber 00195000 | unc 00000000 | 
FE_HAS_LOCK
status 1f | signal 9393 | snr eeee | ber 00195000 | unc 00000000 | 
FE_HAS_LOCK

The last line then repeats itself more or less (slight variations in snr).

According to kaffeine/xine, I have 48-62% signal strength and >90% 
signal quality on all channels.

Thanks for any insights.

Thomas






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