Before buying G400TV, Q's on dropped frames

[Blaq]

After many days of research throughout the year, I decided my next computer would be Marvel G400-based. When I buy it next month. I want to make absolutely sure there will be no dropped frames. I have several dealers willing to test the assembled system, tweaking it until a 30-minute hi-res, hi-quality capture shows _zero_ dropped frrames.

In another thread dealing with massive frame drops, the user wrote "The Matrox PC/VCR Remote (as always) reports 0 dropped frames." This means I won't be able to use PC/VCR statistics at the store to test whether any frames were dropped. What utility should I use, then? What parameters are available when digitizing (so I know exactly what to have them write on the invoice as acceptance test) And are there any other aspects to dropped frames I should be aware of? Thanks.

[Dr Mordrid]

With analog video a drop here and there is almost inevitable, so expecting none is unrealistic. Even so, my system can often capture over 100,000 frames with no more than a few dropped frames, and even then AVI_IO covers those nicely. More on AVI_IO later....

Frame drop problems are most often related to four major factors;

1. bus contentions

Bus contentions most often come into play when you see IRQ conflicts or ISA emulation turned on with PCI audio cards. Also problematic are PCI cards that may contend for resources at critical times like a modem or NIC. The best way to handle these things is to create an editing-only profile with these devices disabled.

2. Windows limitations:

The Win9x optimizations found on Matrox's site are very helpful;

http://www.matrox.com/mga/support/fa.../video4.cfm#33

3. VIA chipsets

VIA chipsets come into play mainly with Super7 systems because of proven bugs in these chipsets. ALi chipped boards are a bit better, but still have problems as these two chipsets are very closely related. The problem comes down to low PCI bus performance and problems in their cache pipelines.

Unfortunately VIA chipped boards of all types tend to lower PCI performance than their Intel equivalents.

4. low performance drive subsystems

Drive speed isn't usually a problem with MJPeg when using the newer ATA66/100 7,200 rpm drives. Where I see it crop up is when attempting to capture uncompressed (YUY2 or RGB) video on a single drive. There just isn't enough extra performance to do this. Consequently RAID0 arrays are very helpful when using these modes (Fasttrak100 + 2-2 ATA100's works great).


Now for the rest....


Capture modes:

The capture modes for the Marvel G400-TV are;

MJPeg: 176x120, 352x240, 352x480, 704x480

MJPeg has several quality settings for each linear resolution. These range from 6.6:1 to 16:1 compression for 704x480.

YUY2: this is a capture mode that (for now) requires a patch program to activate, but is rumored to be on the full-support list for future driver releases. This makes sense as YUY2 is the native capture mode of the card. Its available resolutions are the same as for MJPeg.

RGB: 320x240, 640x480. RGB is derived from the native YUY2 capture mathematically.

CPU performance comes into play when capturing uncompressed using an alternate compressor. I recommend a PIII/Athlon of 750-800mhz minimum if you want to do full frame realtime encoding.

Capture programs:

As far as capture utilities go most of us don't use PC-VCR. AVI_IO is the capture proggie of choice for several reasons;

1. it copies the previous frame into a dropped frames slot so the frame count stays right. This keeps the audio in synch.

2. even though it does #1 it still reports the drop.

3. it can get around the 2/4 gig capture limit by capturing serial files without loosing a frame between them. This makes long captures easy.

4. it can use alternate compressors. If one has YUY2 captures enabled this means capturing in YUY2 uncompressed, YUY2 + Huffman encoding or even MPEG-4/DivX.

5. it can also play back serial captures from a playlist.

Dr. Mordrid



[This message has been edited by Dr Mordrid (edited 24 September 2000).]

[Pytkin]

BLAQ.. If i capture in MJPEG , Im everytime getting drops .. If I capture YUY2 or RGB , then no drops here ..

[rei]

Still trying to find someone with a used Marvel G400TV who wants to sell...(sigh)

[Riddek]

rei,
Did you try cjyo~ in this forum with the post "Marvel to RT2000 Upgrade Questions"? Now that he'll soon have the beautiful RT he might be looking to sell his Marvel.