aspect ratio slightly unexpected

[boaby]

i have an mpeg i captured with my dvb-t card which im trying to xvid so i can archive it. with the mpeg in media player classic, the properties dialog reports 720 x 576 (AR 16:9).

so, using vdub-mpeg2 i took the mpeg, cut out the commercials, set audio to mp3, set video to xvid two pass, used a de-interlace filter (blend) and encoded out an avi.

the resulting avi was good except the aspect ratio was off, it lost its widescreen attributes - in mpc the properties dialog still reported 720 x 576 but minus the 16:9. now, within mpc/vlc i can force it to stretch to 16:9 and it looks like the source but im wondering why it isn't like the source by default.

question: does the above mean my source mpeg is using non-square pixels? and how can i encode it so my xvid appears in the same ar by default (i.e. no need for stretching through playblack)?

any help with this would greatly appreciated....thanks

[jagabo]

AVI doesn't really support aspect ratios. But individual codecs can include aspect ratio data that players can use. If you set the Xvid codec's picture aspect ratio to 16:9 many software players will display it properly. Most set-top players will not.

If you want a 16:9 picture on all display devices use VirtualDub's resize filter to resize the frame to a 16:9 ratio -- like 640x360. Then players that assume square pixels (most of them) will display with the proper aspect ratio.

[boaby]

cheers for the reply jagabo, ill try the resize.

just a couple more questions tho:
- in vdubs filter dialog, when using both the de-interlace and resize filters, would it matter what order they were placed in?
- and would you recommend a specific resize mode eg. lancoz, bicubic, etc?

cheers.

[jagabo]

- in vdubs filter dialog, when using both the de-interlace and resize filters, would it matter what order they were placed in?

Yes, you should deinterlace first. But I don't recommend deinterlacing if you can avoid it. VirtualDub's blend deinterlace gives a fuzzy picture and when there is a lot of motion everything looks like a double exposure. Try a smart deinterlace filter like this one:

http://neuron2.net/smart/smart.html

with the Edge Directed Interpolation option. It works much better on most material.

- and would you recommend a specific resize mode eg. lancoz, bicubic, etc?

You almost always want to use Lanczos3 in VirtualDub.

Nearest Neighbor simply subsamples pixels. For example if you reduce the size by half (in one dimension) it will simply use every other pixel. This leads to a sharp picture but very bad moire patterns.

Bilinear is better than Nearest Neighbor but leads to a little blurring and a fair amount of moire. The results of Bilinear resizing compresses a little better than the others though.

Bicubic gives a sharp result but lots of moire patterns when shrinking.

Lanczoz3 gives sharp results and very little moire.

[boaby]

thanks jag. thumns up