[linux-dvb] Hauppauge WINTV Nova-T 500 PCI

Sid Boyce sboyce at blueyonder.co.uk
Sat Sep 1 12:19:14 CEST 2007


Maillist wrote:
>>> Joacim wrote:
>>>> I executed dvbsnoop (with -s singal) during a scan and when finding channels
>>>> I
>>>> got:
>>>> Sig: ~46000
>>>> SNR: 0 (?????)
>>>> BER: 0
>>>>
>>>> Can I trust the values from dvbsnoop?? Any better tool??
>>> I use femon from the dvb-tools package (or the VDR-plugin named the same).
>>>
>>> /Richard
>> I tested 'tzap' and 'femon'
>>
>> root at frodo:/home/joacim# tzap -a 0 "Nickelodeon"
>> using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
>> tuning to 594000000 Hz
>> video pid 0x03bf, audio pid 0x03be
>> status 0b | signal 8fff | snr 0000 | ber 001fffff | unc 00003c4c |
>> status 1f | signal 9036 | snr 0000 | ber 00000000 | unc 00002347 | FE_HAS_LOCK
>> status 1f | signal 9040 | snr 0000 | ber 00000000 | unc 00003e98 | FE_HAS_LOCK
>> status 1f | signal 902e | snr 0000 | ber 00000000 | unc 00003c57 | FE_HAS_LOCK
>> status 1f | signal 9014 | snr 0000 | ber 00000000 | unc 00003efe | FE_HAS_LOCK
>>
>> root at frodo:/home/joacim# femon -a 0
>> using '/dev/dvb/adapter0/frontend0'
>> FE: DiBcom 3000MC/P (TERRESTRIAL)
>> status 1f | signal 8e6e | snr 0000 | ber 00000000 | unc 00003ef9 | FE_HAS_LOCK
>> status 1f | signal 8e6e | snr 0000 | ber 00000000 | unc 00003ef9 | FE_HAS_LOCK
>> status 1f | signal 8e6e | snr 0000 | ber 00000000 | unc 00003ef9 | FE_HAS_LOCK
>> status 1f | signal 8e6e | snr 0000 | ber 00000000 | unc 00003ef9 | FE_HAS_LOCK
>> status 1f | signal 8e6e | snr 0000 | ber 00000000 | unc 00003ef9 | FE_HAS_LOCK
>>
>>
>> I get SNR 00000 with both apps, singal varies a bit between them.
>> Is it possible to get SNR info out of Nova-T or could it that bad ???
>>
>> --
>> Regards
>> Joacim
>>
> 
> One other question (since I don't have total grip of this area).
> I have also 2 Dreamboxes and those are showing:
> SNR: 99%
> AGC: 60%
> BER: 0
> 
> SNR, I understand quite well I think. Higher values means better quality and
> less noise. I should not only focus on high values but also a stable value.
> 
> AGC, I don't understand. Can someone explain this??
> 
> BER, I think I understand this, Bit Error Rate means errors in the signal that
> could not be interpreted by the receiver. Should be as low as possible.
> 
> Please correct me and/or fill in to increase my knowledge :)
> 
> Regards
> Joacim
> 
> 

In a nutshell, AGC (Automatic Gain Control) attempts to present a 
constant signal output, it's a compensation loop. If the received signal 
rises beyond a certain level, AGC acts to attenuate it, if the signal 
decreases, e.g due to fading AGC acts to amplify the signal. Constant 
voice/video output for a large variation in received signals.
Regards
Sid.
-- 
Sid Boyce ... Hamradio License G3VBV, Licensed Private Pilot
Emeritus IBM/Amdahl Mainframes and Sun/Fujitsu Servers Tech Support 
Specialist, Cricket Coach
Microsoft Windows Free Zone - Linux used for all Computing Tasks




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