VideoStudio 6 MPEG "buffer renders"....

[Dr Mordrid]

When VS6 does a DV->MPEG capture and it stops to render the video this is because of a buffer under-run.
When the buffer fills up VS6 stops the device control, renders the buffer and then picks up the capture where it left off; continuing to capture until the buffer fills up again and the process repeats.

When you think about it this is a pretty good feature.

Now....there are two ways to avoid a buffer under-run;

1. a fast CPU, preferrably an AthlonXP or P4, so the encoding is faster than the frame importation.

2. instead of using the canned DVD profile use one of the "user defined" capture profiles to create a custom setup.

I set up MPEG-2, Performance = 1 and a VBR bitrate at about 5r00 kbps. Otherwise the advanced settings were the same as with the normal DVD profile. Slightly lower quality, yes; but no halts for buffer under-runs and a true realtime MPEG capture.

I used this setup to capture >85,000 frames without stopping to render the buffer on a PIII/850. There were NO dropped frames either. The resulting MPEG file was about 1.8 gigs in size.

In BitRate View the Q and bitrate graphs were about what one would expect for VBR but without wide swings out of the playground, peaking at about 6 and 4900 kbps respectively. The DC Coefficient was reported as being 9.

Dr. Mordrid

[fberger]

Doc,

I was intrigued by your comments and decided to give VS6 a try. I chose a PAL 8 mm tape that I wanted to convert to VCD or SVCD using my Marvel G200 under Win98. I tried two things:

1. VCD: I selected the VCD PAL template and set the MPEG performance to 15 (I have a fast system and it's MPEG 1 anyway at low res). This should have given me the highest quality, but the result was a disaster, I get large squares even in scenes without motion.

2. SVCD: the Matrox driver does not allow me to select a capture size compatible with SVCD PAL (480x576). VS6 rejects all attempts to capture and convert to MPEG on the fly.

Is there another solution I am missing? I was hoping to take advantage of the new Ulead "on the fly" MPEG compression to quickly convert all my tapes.

Fred

[Dr Mordrid]

I think using a Performance setting of 15 out of the box was a bit of a stretch

Try using 2-3 first and see how that goes. Then try going up a step at a time 'til you have problems then back off 1 step. Methodical is the way to go in these things.

When doing SVCD import the footage and set up the project as 704x480/576 MPEG-2, then when done editing export it as an SVCD file.

The resulting MPEG will *seemingly* play as full width video in MediaPlayer and VS6, but that's because it's anamorphic. That means it's actually 480x480/576 but plays full screen.

I can import these into DVD MovieFactory and they are accepted as SVCD formatted files. When I load them into BitRate View they are also identified as 480x480/576.

Why not capture to 480x480/576 to start with? First of all your Matrox card doesn't support a 480 capture width as a standard feature.

Even so some software (AVI_IO, VirtualDUB) can do this using the YUY2 704x480/576 mode (has to be activated by using a driver patch) and by setting a custom frame size. You can get the driver patch here;

http://www.murc.ws/Utils.html

Look for Flying Dutchmans YUY2 patch.

Even if VS6 could do custom frame sizes the rub comes in the amount of time it takes to encode MPEG. This is not so short and very resource heavy. This makes scaling to an odd width like 480 (2/3 the full frame width) too time consuming to work in realtime when you're trying to encode MPEG on the fly too.

Scaling captures to VCD is no problem. All you do is drop a field (this does the vertical scaling) then drop half the horizontal color samples (each is 2 pixels wide, so you don't lose anything) before encoding the result. This can be done very fast just by shifting bits and thus can be done in conjunction with realtime MPEG capture.

Dr. Mordrid

[fberger]

You are right, in fact I started with performance=7, then since I wasn't satisfied with the quality I tried 10 and did not see any difference, so I moved it up all the way to 15 and still I could not see any difference at all. I thought I might have it wrong so I also tried with 1 and did not notice any difference. The trial version is supposed to be the real thing, except for the 30 days expiration, right? Or is the MPEG engine "crippled"? How is quality supposed to vary when going from 1 to 15? What should I look for?
The VCD video looks ok on the computer, but I see all those squares when playing it on my Pioneer DV343.
My goal here was to avoid a conversion step from full frame PAL to the SVCD or VCD resolution.

Another problem I found when capturing full frame and then letting VS6 convert to SVCD is that it creates lots of lines in the output file. My guess is it's a field order issue, but VS6 does not seem to give you the option to change that like in MSPRO.

Thanks for the suggestion on VirtualDub and YUY2, that's what I have been using until now to avoid a full frame capture. If only I could add a realtime MPEG compressor it would be perfect. But from what you say since all this processing is done in software it can't be done in real time yet.

In conclusion there does not seem to be a way to process my 8mm tapes to VCD or SVCD in one step with a Matrox G200. The limitation seems to come from the Matrox card. Do you know of any other analog capture card that would provide an affordable way to capture directly at a width of 480?

Fred

[Dr Mordrid]

NTSC DV uses field A. PAL may be different, but since I'm not in PAL land.....

In either case you can change this by using a user defined setup, which allows you to set all factors including field order.

480 wide captures can easily be done with the WinTV cards using their VfW drivers and AVI_IO's custom frame feature.

Dr. Mordrid