how do I get 29.97 frame rate with Virtual Dub??

[mojo]

Ok, I've tried everying!

I'm trying to cap at 29.97 at 640x480 with a USB 'AlterTV' device.

I've disabled all previews, made sure DMA is on, rebooted and turned off all other apps. I'm running a 1.2 gig Athalon with a gig of ram and VD reports that my proc during cap isn't being pushed past 50%.

I've got plenty of HD space and using Huffy (oh and Win2k) but I still only capture just over 29 fps, so my resulting files are very choppy.

Any suggestions?


Mojo

[kinneera]

The Huffyuv codec is very bad at playback, but it doesn't necessarily mean anything is wrong with the video. It is popular as a lossless intermediary to be encoded to another format. Try encoding a part of your video to MPEG and you'll probably be pleasantly surprised.

[mojo]

I tried what you suggested, but the MPEG played back equally as choppy.

My frame rate averaged around 29.2.

One thing I don't understand - is the framerate actually changing constantly, as Virtual Dub displays during capture? Doesn't that make it more or less impossible to get smooth playback? I would think that, if it realized it couldn't cap at 29.97, it would pick (or suggest) a lower frame rate and stick to it.

Still, I don't know why I can't encode at 29.97. My CPU isn't being taxed. Also, when I pick another form of compression (like DiVX) the frame rate goes way down, to maybe 15.


Mojo

[kinneera]

Upon re-reading, I noticed you are using a USB device...so my question is this: is it a USB 2.0 device? If not, I suspect your problem might be one of data rate. USB 1.0 can only handle about 12 Mbits/sec, which works out to about 1.5 MB/s. Huffyuv, on the other hand, produces a data rate of 6.5 MB/s when I use it to capture at 480x480, which is less than what you are attempting. I can't think of any other explanation, maybe someone else can help out here.

As for Divx, you really shouldn't use it for capturing - the level of processing required is extremely high, and doing it realtime will simply never produce very good results (also responsible for the substantial framerate drop).