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Nebula dropout when recording


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Very new at this so apologies for dumb questions. I've found this forum invaluable in researching what to buy and now I've purchased it's also helped me sort out some setup issues!

I'm after some help on isolating a problem I'm having when recording any broadcasts (SD or HD). My setup is far from ideal as you'll see below but I'm trying to work out which bit is causing me the issue. The issue is that any recordings (either silent or otherwise) are very scratchy. I can watch the broadcast without recording fine (with dropouts every now and then) but as soon as I record it becomes reasonably unwatchable.

Here is my setup...

Athlon XP 1800, 256MB RAM

16MB Nvidia video card

DigiTV v3.12b3

Reception for 7 SD is about 75%, 25 SNR, BER 0.226. My PC is about 10m from the antenna outlet and I'm using crappy extension COAX to run to the PC.

I've got a wireless router on the desk with the PC under it. I turned this off and it didn't seem to make any difference so I don't think it's interfering.

Again, I'd appreciate any help on which is the best part to fix first. Is it my old video card, or the CPU or the reception strength? I plan to build a whole HTPC and this is the first step.

Thanks

Nick

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Reception for 7 SD is about 75%, 25 SNR, BER 0.226. My PC is about 10m from the antenna outlet and I'm using crappy extension COAX to run to the PC.

Hi Nick,

I would try and improve your reception first, starting witht the "crappy cables"

Bring the BER down to around 0.01 or so and see how you go.

Cheers

Renura

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Welcome to the forum.

I'll second Renura's comment about your antenna cable. :blink:

What motherboard model and hard disk are you using? If you hit the 'i' key to bring up the statistics overlay, are you seeing large number of H/W FBUS errors - particularly when recording?

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Try using a good quality RG6 cable between your antenna outlet and PC.

You may also want to adjust your antenna.

If you have a good quality analogue reception it doesn't necesserily means that your digital reception will be good.

I had to move my antenna by 45 degrees before my channel 10 BER dropped down to a reasonable level.

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Sholefn

As the others have stated reliable reception is likely at BER's down around 0.01. In some of my best cases a BER of less than 0.007 can be achieved.

It's odd that you have SNR at 25 and BER at 0.226. There may be interference or multipath reception etc

One thought also is make sure your power cables to the PC are separated from the antenna fly lead as much as possible. If as you say the coax is 'crappy' this may be one source of interference. The PC itself could be the source of interference as well

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Thanks.

I pressed the 'i' key and the number of h/w FBUS and h/w FDSR errors increased dramatically when I started recording.

My motherboard is an MSI K7T266 Pro 2A. I've got 2 hard drivers, 1 a 40gb Maxtor and the other a 120gb WD. I have DigiTV installed on the 40gb and have tried saving to locations on both the 40gb and the 120gb with no difference.

I'll definitely look at a better cable to try and get a better reception as well but I presume the large number of h/w errors point to something other than reception for the recording issue?

Nick

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NIck

Sounds like you have hardware conflicts between the card and your motherboard

What types of disk controller are built into the board ?

Problems with Promise ATA and SATA, and Silicon Image RAID Controllers are reported elsewhere in the forum

Look at that as a start. and also look to move the card to different PCI slots and see if it improves.

If you use XP's System information function look to see how the interrupts are allocated and shared. Something may be obvious there

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OK - fixed the reception. Went to DSE and bought a 10m RG6 cable and the BER is now just over 0.01 which is much better!

Still having the choppy recording problem. It sounds like what MurrayT is describing, eg. a conflict somehow between the disk and the DVB card. I don't think I've got SATA disks. I've checked everywhere I know how and it looks like the controller is a 'Standard IDE ATA/ATAPI controller'. The transfer mode is 'DMA if available'. I haven't changed it to 'PIO only' to see if that makes any difference.

There's no obvious conflicts in the device manager either.

I'm starting to get a bit out of my depth....any other suggestions? Thanks again for the help to here!

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Which IRQ's are assigned to HDD controller? It should be 14 for Primary and 15 for secondary IDE controller.

Do you use 80 wire IDE cables? If you use only 40 wire ones, the HDD transfer rate will be limited to UDMA 33 only.

Which IRQ is assigned to the Nebula card? Is it shared with another device? Check the System information tool in Accessories/System Tools.

Do you have the latest VIA Hyperion drivers installed?

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OK....

The primary IDE controller is on 14 and the secondary on 15. Both the disks are on 14 as one is a slave of the other. I'm only using the master at the moment now anyhow for DigiTV.

The NebVideo is on 17 (there are 2 - Video capture & audio/mpeg2 capture). It was shared with my Firewire card but I've disabled this through the device manager and rebooted. It's now on its own. Do I need to actually uninstall the firewire card or move its PCI slot rather than just disabling?

Not sure about the IDE cables. I just looked at them and they seem to have about 40 wires I suppose?

I have installed the latest VIA hyperion drivers but that didn't help.

Thanks again for the help.

Nick

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In the Device Manager/IDE ATA Controllers/Primary IDE channel/Advanced Settings, does it say Ultra DMA 5?

If not it means that you don't have 80 wire IDE cable or it's not correctly detected by the BIOS.

What does the BIOS say?

Sometimes hard disks don't like to work in master/slave configuratio n.

Try disconnecting the HDD and DVD/CDROM you don't use. Try also removing the firewire card and all other cards you don't use.

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  • 2 weeks later...
Guest utedog1503559859
Thanks.

I pressed the 'i' key and the number of h/w FBUS and h/w FDSR errors increased dramatically when I started recording.

My motherboard is an MSI K7T266 Pro 2A.  I've got 2 hard drivers, 1 a 40gb Maxtor and the other a 120gb WD.  I have DigiTV installed on the 40gb and have tried saving to locations on both the 40gb and the 120gb with no difference.

I'll definitely look at a better cable to try and get a better reception as well but I presume the large number of h/w errors point to something other than reception for the recording issue?

Nick

Hi I had a similar problem than you. When I watched a live broadcast on the projector, I had no glitches, but as soon as I started to record in parallel, it was starting to drop frames ocassionally. This still happened after I replaced it with a new higher aerial and cabeling. However, I fixed it just last night. The only two things I've changed are upgrade to DigiTV 3.12b4 and also tick high priority in the video engine settings. See if that helps you. I've run a couple of trials now, not a single dropped frame while recording and watching simultaneously.

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Thanks utedog. My problem's more serious than that. I'm getting a conflict between the hard disk controller and the Neb card that I've tried everything to fix to no avail. Basically whenever there's any disk activity I lose lots of signal and get lost of h/w errors.

Time for an upgrade anyhow so I'm looking at picking up a new m/board and Athlon 64 this weekend! I think this approach is called 'the tail wagging the dog!'.

Nick

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Thought I'd close this story off!

I've now got a new motherboard (Giga-byte GA-K8VM800M based on VIA KM800 chipset) and chip (Athlon 64 2800). Apart from getting the 'cannot attach to hardware surface display error' when I first installed it (at which stage I was ready to cry), everything's working great. I fixed the 'surface display error' by changing the hardware overlay format (although this setting change doesn't work in 3.12b4 - see my post in the Beta 4 thread).

So - good trigger to upgrade everything!!

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Thought I'd close this story off!

Not so fast!

everything's working great

That's not normal; let's see if we can fix it :blink: Have you enabled the clockspeed/voltage throttling feature (aka "Cool 'n' Quiet") of the CPU?

One person has reported issues between this feature and DigiTV. Thinking of getting the an A64 myself (CnQ being one of the main reasons) and I'm interested in whether this is an isolated problem or a more general incompatibility.

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One person has reported issues between this feature and DigiTV. Thinking of getting the an A64 myself (CnQ being one of the main reasons) and I'm interested in whether this is an isolated problem or a more general incompatibility.

As I mentioned here we're also interested in finding out what exactly the source of the problem is - I suspect that whatever is going on, it may not be isolated to DigiTV but may well be a general RFI issue that impacts tuner cards in general. I'm also interested to know if people with DVB-T USB devices observe similar behaviour with CNQ enabled.

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Hi

I think you're asking whether the AMD Cool n' Quiet functionality is working?

I've now installed the updated CPU drivers as per the Giga-byte link (thanks for that!). I can't get the AMD software (PowerNow Dashboard) to work and show me the speed changing but there is a graphical tool that came with the motherboard that reports the CPU speed.

When DigiTV is running the CPU is running at 1800MHz (which is the standard). When I shut DigiTV it drops to around 1000MHz. I'm not having any issues with dropouts etc. in DigiTV. So, it would appear that it's working.

Hope that helps.

Thanks

Nick

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