Virtual dub probs (6 to be exact)

[solipsismx]

Okay somebody directed me to virtual dub (can't remember who but THANK YOU) and it saved me the cost of a new tv card. Anyway, I have a couple simple questions.

1. Is the benchmark test pretty accurate with you guys? Because when I run it, I can do some pretty hefty capturing, yet when I actually try this kind of capturing, my computer skips over tons of frames.

2. What the heck is a video buffer limit? My default settings were set on 10 for buffer limit and it dropped frames like crazy. But when I bumped it up to 1000 it ran smoother. Should I keep it at 1000 or should I try to keep it as low as possible without a frame drop? Also, what would be a good audio buffer limit if I'm only capturing in 44hz 8 bit mono (it's a skate video so the audio isn't too important)?

3. The I/O also confused me. It has chunk size and chunk limit I think. What should I have these at? Keep in mind when I capture I use the capture (compatible) option (f5).

4. My comp is 1ghz p3 with 340 megs of RAM. I know that this isn't exactly top of the line anymore, but it seems like I should be able to capture some above average video. Yet capturing at higher resolutions is very inconsistent Sometimes it runs beuatiful, and sometimes it's terrible even though I swear I had the same settings. Judging by my computer specs, would you guys say the settings I'm using are the problem, or that this is pretty normal for a computer in this range?

5. Can you guys recommend the most efficient compressor?

6. Keyframes: I read the help file on it and I'm still a little confused. The amount of keyframes defaults on 15, so this means every 15 frames is a keyframe right? So that means that if I lowered it to 2, it should be higher quality right? If this is true, how come it takes longer to process captured video when I put "2" in the keyframe option? Wouldn't it mean that the computer has to generate less delta frames? Because if I capture without any compressors (which means no delta frames right?) I don't have to process anything at all.

thanks for taking the time to answer these newbie questions

[sommersby]

you should keep your capture limit to 90% cpu usage, close all background running apps, especially antivirus software, DO NOT touch the keyboard or mouse to do anything except stop the capture. This should result in more consistant captures.

[sommersby]

As far as compressor, I use huffuv most of the time but also like picvideo and the encoding runs a bit faster using picvideo and uses about half the disk space but to get good quality with picvideo you need to be able to capture at 640x480 at a quality setting of 15 or higher, you can good results with huffuv with a smaller capture resolution since it is a lossless codec.

[dattrax]

Just to answer keyframe issue (6) Keyframes are often more expensive in terms of bits used, so bandwidth to the disk would be increased at this point. There are issues with the compressor you have chosen, for example MPEG4 would reinit AC/DC tables at a keyframe (I would guess, as I've only ever written decoders). Try to use an MJPEG codec, as effectivly all frames are keyframes, but there are some very good software codecs out there.