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 Post subject: Third Tuner Problems
PostPosted: Mon May 28, 2007 6:46 pm 
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Joined: Thu Apr 20, 2006 10:06 pm
Posts: 7
Location: Newcastle, NSW, Australia
Well I think I have search just about everywhere without any success, so it's time to make a post. I have been trying from ages to get a third tuner going in my system and have gotten nowhere.

My setup is as follows.
AMD 2500+
1Gb RAM
2 x 200Gb IDE HDD
3 x BT878 Tuner Cards (Avermedia 771/Twinhan Mini Ter)
Nvidia Video Card
Epox 8RDA3+ Motherboard
Onboard Sound.

The system work perfectly with 2 tuners, no problems at all. When I configure the 3rd Tuner it still works until all three cards become active. For example I can be watching a channel with PiP on and the system is working fine, as soon as I start the third card recording all three cards start to flake out, break up like if it had poor signal. Also does this if all three cards start to record something. Usually the backend will crash after 5-10min, the error logs show nothing unusual.

I purchased the 3rd card well over 12 months ago and put my initial problems down to the version of knoppmyth that I was running as I had not upgraded in awhile, being a production box it's taken me this long to do something about it, I upgraded to R5F1 with high hopes that it would solve my problem, alas it has not.

The twinhan cards were showing some error messages is syslog relating to PCI issues (something like irq FDSR). I have tried swapping PCI slots around, and I have even managed to make all three cards identical in make (all Avermedia 771's) by borrow some friends cards. This eliminated the errors in syslog but didn't resolve the problem.

I have eliminated signal strength as the issue, I am using an active splitter, the cards are reporting 98% strength and I can tune 3 cards if I move one of the cards to a Windows PC.

Using the RRD monitoring in the latest release I can see that the CPU, Memory, etc are not being overloaded as they barley move at all.

My thought after checking these was that maybe the HDD's were not able to keep up with the speed of three DVB streams being dumped, but running Bonnie on the system peaks the HDD monitor allot higher than it goes when all 3 cards are active, so much so that they become small blips in comparison.

The only other thing I could find any reference to was possible PCI Bus contention, I am not able to rule this out, but I am running the latest BIOS for the motherboard and I can't really test this any further without purchasing a new motherboard (not something high on my list todo).

Anyway, thanks for reading, I am just hoping someone out there run into this problem that they might not have posted about and is able to offer some form of solution or advice.

Cheers,
Beau


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 Post subject:
PostPosted: Mon May 28, 2007 9:14 pm 
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Joined: Tue Mar 22, 2005 9:18 pm
Posts: 1392
Location: Brisbane, Queensland, Australia
Whilst I can't offer any direct advice, I would like to suggest to you this. The problem (What I think anyway) is a problem with IRQs in that with two cards they are on separate IRQs and when you add the third card it is sharing its IRQ with another one of the cards.

In some BIOSes you can set the IRQs for the PCI slots and what you may find is that some of the slots may be shareing IRQs. Unfortunately due to the limited number of IRQs it can sometimes be difficult to free up to have enough unique available for what you need.

Also in the BIOS turn off things that you don't use, such as serial and parrallel, games and midi ports. This will hopefully free up an IRQ or two and allow you to set a unique IRQ for each of your PCI slots.

I am going to download the manual and have a look and see if these options are availabe. I will post back what I find for you.

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 Post subject:
PostPosted: Mon May 28, 2007 9:48 pm 
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Joined: Thu Apr 20, 2006 10:06 pm
Posts: 7
Location: Newcastle, NSW, Australia
Hi Girkers,
Thanks for the reply, I have played around with the IRQ's, I’m a computer tech for a living so have a good knowledge of most things hardware. There are a couple of "shared" PCI slots on the board and I was able to get all three tuners using unique IRQ while testing PCI slots, they are however sharing IRQ with some "other" devices. I have also disabled any onboard device that was not needed.
I can't say with certainty that it is till not IRQ related, but I am fairly sure they are not interfering with each other, any because they all work individually I am fairly sure they are not having any issues with sharing IRQ's with other devices.
I can’t remember what the hardware IRQ assignments are from memory, I will check when I return home tonight, the software assignments for the tuners are IRQ 19, 20 & 21.
Thanks for the advice and looking into it for me, if you find something that I am missing it will be most appreciated.

Thanks,
Wob


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 Post subject:
PostPosted: Mon May 28, 2007 9:50 pm 
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Joined: Tue Mar 22, 2005 9:18 pm
Posts: 1392
Location: Brisbane, Queensland, Australia
Looking at page 4-21 of the manual you will see that Slot 1 shares with Slot 5 and Slot 2 shares with the AGP port. Could I suggest as a test put the tuners in slots 3,4,5 and have nothing in slots 1 & 2.

This way it would appear that non of the devices will conflict with each other. good luck.

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 Post subject:
PostPosted: Mon May 28, 2007 9:59 pm 
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Joined: Thu Apr 20, 2006 10:06 pm
Posts: 7
Location: Newcastle, NSW, Australia
I'll give it a try tonight, I have tried most combinations of slots with my previous release of Knoppmyth, but it may well have been a combination of problems so I'll try again tonight and let you know the result.

Cheers,
Beau


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 Post subject:
PostPosted: Tue May 29, 2007 6:10 am 
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Joined: Thu Apr 20, 2006 10:06 pm
Posts: 7
Location: Newcastle, NSW, Australia
Unfortunately no success with that, all three cards are now in slots 3,4,5 and all have different hardware IRQ's. I will try some more testing but I don't think it is an IRQ conflict between cards. All cards work individually fine and any combo of two will work, but just not all three.

I am thinking maybe it could be a issue with the BTTV drivers, I noted the following line in the syslog.

"bttv: using 8 buffers with 2080k (520 pages) each for capture"

Does anyone know if this is across all the cards, and if it can be tweaked at all? Is there anyone else out there running 3 BT878 based cards successfully?

Cheers,
Beau


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 Post subject:
PostPosted: Tue May 29, 2007 10:35 pm 
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Joined: Tue Mar 22, 2005 9:18 pm
Posts: 1392
Location: Brisbane, Queensland, Australia
[deleted]

[Edit] The orginal post was drival and added nothing of value[/edit]

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 Post subject:
PostPosted: Tue May 29, 2007 11:42 pm 
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Posts: 1206
Location: Silicon Valley, CA
Could this be a CPU problem? As I recall those cards rely on software to create MPEG files on the fly since they have no hardware assist. Maybe the CPU is just too busy to handle three streams?

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 Post subject:
PostPosted: Tue May 29, 2007 11:53 pm 
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Joined: Thu Apr 20, 2006 10:06 pm
Posts: 7
Location: Newcastle, NSW, Australia
Hi Liv2Cod,
Thanks for the idea but it's defiantly not CPU related, these cards are hardware based cards and have little to no effect on CPU usage, I have monitored CPU usage with both TOP and the new RRD monitor in the latest Knoppmyth and both show the CPU doing very little work during recordings.

Keep the ideas coming people.

Cheers,
Beau


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 Post subject:
PostPosted: Wed May 30, 2007 4:26 am 
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Joined: Tue Mar 22, 2005 9:18 pm
Posts: 1392
Location: Brisbane, Queensland, Australia
Wob,

Just a thought, would it be possible to try and get the cards to work outside of MythTV just as a test. What I mean could you use something like xawtv to access one card, open another terminal and open another session of xawtv.

This way you could check if it was mythtv or more like a driver issue. I don't know of an application as such that can do what I am suggesting, maybe xine, mplayer?

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 Post subject:
PostPosted: Wed Jun 06, 2007 5:11 am 
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Joined: Wed Mar 03, 2004 7:43 pm
Posts: 745
Location: Sydney, Australia
Wob76 wrote:
"bttv: using 8 buffers with 2080k (520 pages) each for capture"

Does anyone know if this is across all the cards, and if it can be tweaked at all?

Untested, but try adding something like this:
Code:
options bttv num_buffers=24 buffer_size=65536
into /etc/modules.conf or /etc/mythtv/modules/bttv*

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 Post subject:
PostPosted: Thu Jun 14, 2007 3:03 am 
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Joined: Thu Apr 20, 2006 10:06 pm
Posts: 7
Location: Newcastle, NSW, Australia
Hi Guys,
Thanks for the suggestions, I finally got around to testing some of them but without success.

I was able to get an external tuning application working (Kaffine) and used it to tune the third card while mythtv was using the first two. My problem is still evident. So I am assuming from these results it is either a driver or a hardware issue.

Nigel, I tried you suggestion but it also had no effect.

Still open to any suggestions, I am endeavouring to get my hands on some other hardware that may help me narrow down my problem.

Regards,
Beau


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