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Compro T300 scan problems
http://forum.linhes.org/viewtopic.php?f=15&t=15099		 Page 1 of 1
Author:  nmcaullay [ Wed May 02, 2007 7:59 pm ]
Post subject:  Compro T300 scan problems
Hi there,

I'm almost completely sure that this is not the right forum to post this question, but i cant find a similar forum for the V4L drivers (www.linuxtv.org doesnt seem to run a forum?)

Anyway, if someone can point me in the right direction feel free to ignore the rest of this post.

I have 2 Avermedia 777 cards, working fine within knoppmyth. I have added a third being a compro t300. As the channels were all scanned by the avermedia cards, the compro just takes those settings to watch/record tv in mythfrontend.

My problem is that it will lock onto all but one channel (9-nine digital). I've tried to scan again on the compro card, but it only finds half the channels that the avermedia cards found.

I then used scan (dvb-utils)
Code:
scan /usr/share/doc/dvb-utils/examples/ scan/dvb-t/auPerth

to try outside of myth, with the same results.. not locking on half the channels i know to exist (the same scan using the avermedia cards gets all channels).

I then modified the au-Perth file by increasing and then decreasing the frequency by 166667 to see if that picked up the missing channels... still no luck.

The weird thing is that the compro t300 locks onto all but one channel (9) in mythfrontend, but the scanning cant lock onto many more channels (SBS, 7 etc).

Has anyone got any ideas?

You may be asking yourself, why is he posting, it mostly works... well, if this card gets selected by myth to record on channel 9 nothing gets recorded. I have put the compro card to be the third card, so the likelihood of the third simultaneous recording being on channel 9 is not high. Its just not ideal.

Regards,

Nathan
Author:  bruce_s01 [ Thu May 03, 2007 8:26 am ]
Post subject: 
Does that channel share a mux with any other?
If you had problems with the other channels on that mux, it could be that is being broadcasted at a slightly lower power, or there is some kind of interference on that specific frequency.
If you are having problems with only that channel on that mux it could be that there is something wrong with the particular transmission (if you are anything like the UK now, there is a sever lack of on air monitoring now), or the station bandwidth is too much/little for the reception quality.

It might be worthwhile checking connectors/cables/amplifier/aerial to ensure you are not introducing a possible source of interference.

Bruce S.
Author:  nmcaullay [ Thu May 03, 2007 6:48 pm ]
Post subject: 
Hi Bruce,

Not sure about the mux situation, im not down to that level of understanding just yet. Whats the best way to determine the "mux sharing" nature of my new card?

As for the signal strength/quality, i dont think it could be that, as the two avermedia 777 cards both scan (mythtv-setup) and watch/record (mythfrontend) on the offending channel.

Not sure if its a red herring, but the fact that the compro t300 actually does watch/record most channels (apart from nine), means that it is getting a lock. Why would it be able to lock when watching/recording, but not be able to scan and lock using mythtv-setup or dvb-utils(scan)?

Thanks for your help,

Nathan
Author:  bruce_s01 [ Thu May 03, 2007 8:00 pm ]
Post subject: 
nmcaullay wrote:
Not sure about the mux situation, im not down to that level of understanding just yet. Whats the best way to determine the "mux sharing" nature of my new card?
That's the signal coming from the transmitter. In most DVB broadcasting, each channel is not transmitted on its own, it usually is transmitted in a stream along with several other channels. This is called a Multiplex or mux or in MythTV parlance, a Transport.

nmcaullay wrote:
As for the signal strength/quality, i dont think it could be that, as the two avermedia 777 cards both scan (mythtv-setup) and watch/record (mythfrontend) on the offending channel.

Not sure if its a red herring, but the fact that the compro t300 actually does watch/record most channels (apart from nine), means that it is getting a lock. Why would it be able to lock when watching/recording, but not be able to scan and lock using mythtv-setup or dvb-utils(scan)?
Each different type of tuner has different sensitivities, so if a signal is marginal, one receiver may pick it up well, an other may have real difficulties.
This may lead to problems while scanning, as the tuner is being thrashed it may have problems in tuning in quick enough. If you are using R5E50, there is a setting for amount of delay for each tuner, it may be worthwhile increasing this value. You will need to go into the backend setup, and go into the setup for this tuner, one the buttons (which I can't recall the label for at the moment, not the DiSQ one) should bring up a dialog to allow the setting of this value.

If you are not using some kind of amplification, perhaps an amplifier may help, if you are already, perhaps trying out one with higher power.

But as I said before, it might be worthwhile having a look at your cabling, plugs etc.

Bruce S.
Author:  nmcaullay [ Thu May 03, 2007 8:14 pm ]
Post subject: 
Hi Bruce,

Good Australian sounding name by the way! :)

Ok, so the transport is the key, and the frequency is the main bit from what i can tell.. i have have looked at the transport section of the scanning, and changed from the broadcasters value (191.625 MHz) by +/-166667 to see if that helps. Nothing. Channel nine probably send a bunch of channels (SD/HD/Guide etc) on the same mux.

Just remembered that i read somewhere that the Compro T300 drivers honours the other settings in the transport. Might try setting them to auto just incase some of the other settings are causing the scanning to fail?

I have tried the delay setting (put it upto 50), but cant remember if i did it on the correct card.. will try it again tonight.

I remember that the card didnt seem to fit 100% right into the PCI slot, but seems to be recognised ok... will double check that also.

Thanks for your advice, really appreciate it

Nathan
Author:  Ralphthedog [ Thu May 03, 2007 10:11 pm ]
Post subject: 
I found with my Compro T-300 it didn't like doing a "full" scan when I set up my MythTV box(R5E50).

Try it on "tuned" and enter the frequency of the multiplex you're after (767500000 is my local channel 9 :) ) and set the frequency range (7MHz), might have to scan a few times to lock on if your reception is a bit marginal.
Author:  nmcaullay [ Fri May 04, 2007 2:01 am ]
Post subject: 
Sounds like a plan, will give it a crack...
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