[linux-dvb] Why is telitext not complete although BER is 0

lynx.abraxas at freenet.de lynx.abraxas at freenet.de
Sun Feb 18 10:05:42 CET 2007


On 16/02/07 19:54:45, Richard Scobie wrote:
> 
> 
> lynx.abraxas at freenet.de wrote:
> 
> >This  is  very valuable to know. Sadly I couldn't find any info on this in 
> >the
> >net.
> >What would You recon is ment with "signal strength" and  "signal  quality" 
> >in
> >the  M$  windows  dvb-t  programme?  Would  it  be  SIG and SNR as 
> >reportet by
> >dvbsnoop or tzap?  What  do  the  other values discribe? SNR is never 
> >changing although it is reported. Here is  some  output  of usbsnoop and 
> >tzap:
> >
> >tzap ard
> >using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
> >reading channels from file '/home/lynx/.tzap/channels.conf'
> >tuning to 191500000 Hz
> >video pid 0x0201, audio pid 0x0202
> >status 03 | signal 8675 | snr 0000 | ber 001fffff | unc 00000000 |
> >status 1f | signal 8435 | snr 0000 | ber 00000000 | unc 00000013 | 
> >FE_HAS_LOCK
> >status 1f | signal 8455 | snr 0000 | ber 00000000 | unc 00000000 | 
> >FE_HAS_LOCK
> >status 1f | signal 844e | snr 0000 | ber 00000000 | unc 00000000 | 
> >FE_HAS_LOCK
> 
> The crucial ones here are ber and unc.
> 
> Ideally both should be zero. BER is a measure of bit errors in the 
> stream and up to a certain point, these errors are fully corrected with 
> the original data able to be recovered by using the error correction 
> code which is part of the encoding.
> 
> Once the number of errors exceeds the error correction capability, the 
> picture/sound starts to show visible/audible artifacting and this will 
> show up in the unc - uncorrected errors column.
> 
> I am a little puzzled as to why the second entry in your example is 
> showing uncorrected errors and yet has a ber of 0.
> 
> The ber numbers can be quite useful for fine tuning your dish alignment, 
> particularly LNB skew.

Thanks for all Your answers.

What is the difference between SNR and CNR?

I  also  wonder  why my telitext pages are often not complete although BER and
UNC are zero.
Is telitext in its own stream as subtitles would be?


Thanks again
Lynx





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