[mythtv-users] : Re: Artifacts [solved]

John Pilkington johnpilk222 at gmail.com
Sun Dec 23 16:11:38 UTC 2018


On 23/12/2018 13:23, jam at tigger.ws wrote:
> 
> 
>> On 23 Dec 2018, at 6:41 pm, mythtv-users-request at mythtv.org wrote:
>>
>>> Hi
>>> because some of our channels have been playing games with their names I dropped all channels and rescanned.
>>>
>>> All good EXCEPT many channels, specially HD channels, are plagued with artifacts and chirps and squeeks typical of poor signal quality.
>>> I checked frequency in sql table channelscan_dtv_multiplex and they are identical.
>>> I restored old db with mythconverg_restore.pl and problem is totally gone.
>>>
>>> What can I say or not say to the db that will affect tuning. The stations are correct just apparant signal strength is bad.
>>>
>>> I stress NO hardware or software changes or conections are changed in any way ONLY mythconverg DB changes.
>>> Whatcould be happening?
>>>
>>> James
>>
>> Was the old table created with the same tuner - its possible that a
>> field set previously to auto might need a parameter. The easiest check
>> is compare all the old and new tuning parameters.
>>
> Interedting and may well be of interest:
> 
> I live equidistant-ish to 3 transmitters and in range of another two
> 
> Perth - Willetton https://www.txaustralia.com.au/tvcoverage
> 
> Each scan is different. Trick was to scan (say) 5 times add the results and delete not-good channels.
> One transmitter site did not yield best results on every channel!
> 
> So a chance good scan once upon a time, was just luck.
> 
> James
> 
> PS a note to any developers who may be bored :-)
> 
> 1) it would be nice to be able to see signal-strengths a la scanning to easily select WHICH channels to prune
> 2) It would be nice to be able to edit channel frequencies and match frequencies to channels eg
> 
> scan choose a frequency of 663. 250000 instead  of 663 500000
> sql fiddling to get a list of frequency vs chan

Perhaps a more directive antenna would be a good investment?  And maybe 
one of the freestanding scan programs would give signal strength info.

I get this sort of output at the end of a mythtv-setup scan - and 
usually a 'rescan existing transports is OK, unless some 
spectrum-management has been happening.  It shows modulation type, 
transport freq, channel name, channel number, transmitter ident, country 
ident and dvb parameters.

Now you know which transports you want.  Make a note of them and perhaps 
delete the others?

{{{

2018-10-25 12:35:26.588671 I  Current MythTV Schema Version 
(DBSchemaVer): 1348

qam_64:538000000:5STAR:30:12323:9018:12928:12294=12294:dvb 
1030:cnt(pnum:1,channum:1)
qam_64:538000000:5 USA:21:12323:9018:12992:12294=12294:dvb 
1021:cnt(pnum:1,channum:1)

qam_64:698000000:BBC ONE E Mid:1:12323:9018:4166:4166=4166:dvb 
1001:cnt(pnum:1,channum:1)
qam_64:698000000:BBC TWO:2:12323:9018:4287:4166=4166:dvb 
1002:cnt(pnum:1,channum:1)

qam_64:737833000:ITV:3:12323:9018:8264:8200=8200:dvb 
1003:cnt(pnum:1,channum:1)
qam_64:737833000:ITV3:10:12323:9018:8294:8200=8200:dvb 
1010:cnt(pnum:1,channum:1)

qam_64:602000000:Sky News:233:12323:9018:22080:20544=20544:dvb 
1233:cnt(pnum:1,channum:1)
qam_64:602000000:Pick:11:12323:9018:22208:20544=20544:dvb 
1011:cnt(pnum:1,channum:1)

qam_64:762000000:4Music:18:12323:9018:25664:24640=24640:dvb 
1018:cnt(pnum:1,channum:1)
qam_64:762000000:Yesterday:19:12323:9018:25792:24640=24640:dvb 
1019:cnt(pnum:1,channum:1)

qpsk:514000000:Notts TV:7:12323:9018:32844:32780=32780:dvb 
1007:cnt(pnum:1,channum:1)
qpsk:514000000:POP Max:208:12323:9018:33280:32780=32780:dvb 
1208:cnt(pnum:1,channum:1)

Found 7 transports:   --------->  I can only see 6 here :-)
Channels: FTA Enc Dec
ATSC        0   0   0
DVB       142   0   0
SCTE        1   0   0
MPEG        0   0   0
NTSC        0
Unique: prog 143 atsc 0 atsc minor 0 channum 143
Max atsc major count: 0

}}}

HTH

John


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