[linux-dvb] How does bad reception influence quality of macroblocks?

timecop timecop at gmail.com
Fri Feb 16 00:42:02 CET 2007


> > >Does the type of device influence the qualtity of the recieved stream?
> > >(Why do
> > >devices differ in prices so much?)
> > The only difference would be a more sensitive tuner.
> > If your C/N ratio is high, BER is low/or zero, and no continuity
> > errors in the stream, you're getting everything at full quality.
>
> 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
>
> dvbsnoop -s signal -pd 9 -n 9 -timeout 1000
> dvbsnoop V1.4.00 -- http://dvbsnoop.sourceforge.net/
>    DEMUX : /dev/dvb/adapter0/demux0
>    DVR   : /dev/dvb/adapter0/dvr0
>    FRONTEND: /dev/dvb/adapter0/frontend0
>
> ---------------------------------------------------------
> Transponder/Frequency signal strength statistics...
> max cycle count: 9
> Capabilities: BER: 1  SNR: 1  SIG: 1  STAT: 1  UBLK: 1
> ---------------------------------------------------------
> cycle: 1  d_time: 0.001 s  Sig: 33912  SNR: 0  BER: 0  UBLK: 0  Stat: 0x1f [SIG CARR VIT SYNC LOCK ]
> cycle: 2  d_time: 1.017 s  Sig: 34416  SNR: 0  BER: 0  UBLK: 0  Stat: 0x1f [SIG CARR VIT SYNC LOCK ]
> cycle: 3  d_time: 1.020 s  Sig: 33891  SNR: 0  BER: 0  UBLK: 0  Stat: 0x1f [SIG CARR VIT SYNC LOCK ]
> cycle: 4  d_time: 1.020 s  Sig: 33933  SNR: 0  BER: 0  UBLK: 0  Stat: 0x1f [SIG CARR VIT SYNC LOCK ]
> cycle: 5  d_time: 1.020 s  Sig: 33933  SNR: 0  BER: 0  UBLK: 0  Stat: 0x1f [SIG CARR VIT SYNC LOCK ]
> cycle: 6  d_time: 1.016 s  Sig: 33945  SNR: 0  BER: 0  UBLK: 0  Stat: 0x1f [SIG CARR VIT SYNC LOCK ]
> cycle: 7  d_time: 1.016 s  Sig: 33959  SNR: 0  BER: 0  UBLK: 0  Stat: 0x1f [SIG CARR VIT SYNC LOCK ]
> cycle: 8  d_time: 1.016 s  Sig: 33956  SNR: 0  BER: 0  UBLK: 0  Stat: 0x1f [SIG CARR VIT SYNC LOCK ]
> cycle: 9  d_time: 1.016 s  Sig: 33939  SNR: 0  BER: 0  UBLK: 0  Stat: 0x1f [SIG CARR VIT SYNC LOCK ]

C/N is carrier to noise ratio,
BER in your case seems to be 0, so it probably is so, unless your
driver doesnt support quering that. If BER is 0, you shouldn't be
getting any stream errors, usually.
Windows apps usually don't list BER, at least not for any cards I've used.



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