AutoGK: 640x480 vs. 720x544

[rezonat0r]

Hi! I'm backing up an NTSC DVD (4:3 non-anamorphic TV show) with AutoGK.

I'm confused as to whether or not I'm actually losing any real horizontal resolution if I force AutoGK to 640x480, instead of it's default 720x544.

I will be watching these Xvid's on a 720p projector fed from Xbox Media Center (component output). My instinct is that it is best to keep the vertical resolution same as source, since the projector will be resizing to 720 anyway. Is there really any advantage in encoding to 720x544 for this purpose?

Thanks.

[kentar]

What final file size are we talking about ?
AutoGK will always try to find the highest quality for the choosen file size (1cd/2cd,etc).
Another very important factor is compressibility. Different video sources will have different compressibility ratios. When testing for this AutoGK might have to lower the resolution in order to achieve an acceptable quality for the choosen file size.

[rezonat0r]

These episodes are 45 minutes long and there will be 413.84 Mb allocated to video for each. I'm getting comptest values around 80% @ 720, and 70% @ 640.

After more googling, I came across some more solid information. Since the pixel aspect ratio of NTSC is .91, if you multiply 720 x .91 = 655. So theoretically, if I encode at 640x480 I am discarding about 15 pixels of horizontal resolution.

The 720 encodes do look ever so slightly sharper, but of course you trade some compression effeciency.

Right now I'm just having some issues with jerkiness. It's better with forced normal IVTC mode but still occurs in some spots. I'll have to experiment more and maybe try dvd::rip on linux to see if it can do better.