MPEG2 -> AVI aspect ratio

[ShakyJake]

Hello!

I have the Hauppauge PVR250 video capture card. Here is the problem I'm trying to solve:

I capture my TV shows at a DVD quality setting at 720x480. I then use VirtualDUB MPEG2 version to edit out the commercials, then recompress the video into AVI DiVX format.

However, the problem is that the AVI's aspect ratio is slightly screwed up. If you played the original MPEG full-screen it looks fine, but the AVI is usually squashed or stretched.

Any thoughts on how to adjust this? Thank you!

[neuron2]

It sounds like you are capturing with a DV codec. If so, you need to resize for transcoding to DivX. That is because the pixel aspect ratio of DV is not square while DivX is.

Bottom line: resize the width only by 10/11.

If you are not capturing in DV format, well, ignore this. :D

[Kika]

He owns a PVR250. That means, he is capturing in MPEG2. The AR-Rules for working with MPEG2 are equal to working with DV.

[ShakyJake]

Exactly what are the "Aspect Ratio" rules? Can someone point me to a FAQ?

Also, say I'm recording at 720x480. Is resizing it to 640x480 correct? This is what I did yesterday and the picture looked right. But I want to be precisely correct.

If I resize it by 10/11, it would be 654x480. But that dimension seems oddball -- I am viewing these captures on a PC outputed to a televsion.

[Kika]

I try to keep it simple: Full-D1 DVD and DV are using the same PAR with a Picture-Overscan of 16 Pixels.

If your Source is 720x480 and your Target is 640x480 and you want a perfect AR, you have to crop to 704x480 and to resize to 640x480.

OK, in "real life" the things are a bit more complicated. Do a research on AR and PAR here on the Board, i bet you will find a lot to read.

[neuron2]

Kika is spot on. This is not an easy area even for experts. :(

For a newbie, just try different horizontal resizings until you find one that looks right on your target display. :)