Does anyone do RGB captures with Marvel G400?

[JTurner]

Hi everyone,

Here's the scoop, which you may find strange.

I can't seem to capture 640x480 30fps RGB video -- either in 16bit (18Mb/s) or 24bit (27Mb/s). Even 8bit Grayscale 640x480 30fps (9Mb/s) doesn't work. All formats drop between 45-55% of the frames, both with PC-VCR and Ulead Capture.

What is strange is that I can capture 640x480 29.97fps uncompressed YUY2 without a single dropped frame (20Mb/s). And HuffyYUV works fine too (8.5Mb/s).

So my hard drives are fast enough, but the Marvel isn't supplying the video fast enough.

Am I alone here, or is it possible to do RGB captures?


HuffyYUV is great, but doesn't play back well even on my TB800. And uncompressed YUY flickers green and causes my system to reboot if I try to play it back. I've got enough space to capture RGB, which plays back fine (640x480 30fps plays back OK -- I have rendered this in Ulead as a test).

My system currently has only my 4 hard drives and a Marvel G400 AGP in there (no other cards). I've got an Abit KT7-RAID mobo and am currently NOT using the RAID controller. I seem to be able to read/write to my Maxtor 30GB 7200RPM drives at 30Mb/s without bothering with the RAID -- according to HDTach and playback of raw RGB video. I can't capture large-size RGB, though.

I'd appreciate any ideas. Thanks,
-- JTurner

[JTurner]

FYI...

I should probably add that I've tried the RAID0, and with both Maxtors HDTach benches the array around 40Mb/s average sequential read speed. Sandra2001 reports 40Mb/s write and 45Mb/s read (sequential). Even with the RAID0, I still drop 45-55% of frames.

[Dr Mordrid]

First, video capture 101:

just because your drives check out at 30 mb/s doesn't mean you can capture 27 mb/s video. You need some extra capacity, perhaps 20-25% extra, in order to give you a safety margin. Therefore, if you need 27 mb/s for a given format then you really need something north of 35 mb/s to be safe. 40+ mb/s is where I'd start feeling complacent.

Actually YUY2/HuffYUV is normally captured at 704x480, not 640x480.

RGB capture is very bus and CPU intensive, so if your board is hobbled by marginal bus performance or a slow CPU or both you're screwed. You have a fast enough CPU, but otherwise you have problems.

In your case marginal bus performance is the likely problem. Why? Because of your mainboard.

I know it's a highly touted board, but the KT7-RAID has problems regardless of what you read in review sites. If you check the ABIT newsgroup a LARGE percentage of the messages are calls for help on this one board alone. In my cache it's 263 out of 886 posts. That level is way out of proportion.

Key illustration of above: it's on Matrox's "don't even go there" list for the RT-2000. This does not bode well for for editing analog either. The marginal bus performance and other issues related to compatability and its onboard RAID controller just kill it.

First of all it's VIA chipped, so some loss of bus througput vs. AMD or Intel chipped boards is to be presumed. This is a fact of VIA life.

Also, the KT7-RAID's HighPoint 370 chipset doesn't help matters either. Highpoint chipsets have problems with consistancy of thorughput, regardless if you're setting up the drives as RAID or not. Just the presence of the HighPoint is enough because of design and BIOS problems.

BIOS problems? Yup. Both with the HPT BIOS and that it has problems with its own mainboards ACPI functions. Because of this disabling ACPI might help you a bit. Of course that would also mean installing Win2K in StandardPC mode when the time comes.

Back to its performance. When you graph a HighPoint's throughput using DiskSpeed32 the data rate is all over the map, varying up and down, often 20% or more, in a matter of seconds.

Such things can make a card that tests at acceptable peak levels dip into dangerous territory numerous times per second. A drive that tests at 30 fps peak would mean <23 mb/s during these dropouts. This is a prescription for dropped frames when using high enough data rates.

Also;

HuffYUV is NOT a playback codec!! It is a transitional codec for lossless capture and editing before encoding it another format (MPEG-1/2/4, DV, etc.) for playback.

Dr. Mordrid


[This message has been edited by Dr Mordrid (edited 05 April 2001).]

[JTurner]

I knew I could count on you to fully address every point, Doc.

You are quite right when you say that the HighPoint controller gives unstable performance. The Maxtor 30GB ATA100 7200RPM drives benchmark at 32Mb/s average speed with a minimum of 26Mb/s in HDTach.
When two of them are assembled into a RAID0, the average speed increases somewhat, but the minimum speed stays at 26Mb/s. To me, this does not justify using the RAID0 at all, since I gain little in actual performance and increase my risk for data loss.

Further tests reveal that the Highpoint controller seems to overheat easily. I haven't confirmed this sufficiently, but using HDTach on the RAID0 immediately after starting up my system produces a stable graph. Running HDTach 5 minutes later produces an erratic graph. After shutting the computer off for awhile, running HDTach will produce a stable graph right after booting. I repeated this 3 times. I'm not sure yet if one or more of my drives are heating up or if it's the HPT chip -- but I'm betting on the HPT chip.

As for whether bus performance is the main issue, I'm not so sure. I'm sure you're quite right that the KT7-RAID has bus issues, but can you explain why I can't record 9Mb/s grayscale RGB yet I can play back 27Mb/s 24bit color RGB video? Are reading and writing so radically different from the PCI bus' perspective? Seems to me that this might be more of a Matrox driver compatibility issue.

Oh, and for the record, disabling ACPI in Win98 -- I installed the "fail-safe BIOS driver" -- didn't make a difference.

By the way, what Mobo is currently in your system?

Thanks,
--JTurner