I know that I am not supposed to go over 100% and am supposed to stay as close to 100% as possible with the W-Zoom and H-Zoom values in Gordian Knot. I'm, however, not sure what the H-Zoom and W-Zoom values mean. What do they refer to and why is it important to keep them equal to or below 100%? Thanks for all replies in advance.

It is how much you resize the picture. Your standard PAL DVD will have a resolution of 720x576. The zoom values are calculated after aspect ratio correction and cropping.

Resizing to more than 100% will not give you more details and will make encoding take longer.

There may be reasons to upscale though. Most of the time you will loose (true) vertical resolution when correcting the AR which perhaps you want to keep and so you have to horizontally stretch the movie to obtain a correct AR. Or perhaps the movie is just so compressible, that you want to spend some extra resolution to have a larger number of macro blocks per frame so that the on-screen area of one macro block gets smaller. Thus a glitch in one macro block will be less obtrusive. On the other hand you will probably have more glitches than with a lower resolution. I don't think there has been a conclusive result. I'd say most people go the lower resolution route because it is faster to encode.

On the few recent DVD rips I've done, I just cropped the black bars and encoded anamorphically. Usually this will demand for more bitrate but since I allways want to keep the ac3, I go for 2+ cds anyway.

So I'm not hurting the quality of the video any by exceeding 100% in the H-Zoom and W-Zoom values? I have one video that when I use a 640x272 resolution the H-Zoom value is 103%. I have to use a 624x272 resolution for the H-Zoom value to become 100%. I thought I was hurting quality by going over 100% in the H-Zoom or W-Zoom value.

I generally encode my movies using a width of 640 or 512 depending on the movie. So my standard resolutions are usually 640x272/352 and 512x288, etc. And, it may sound stupid, but I would like to keep my resolution for this movie uniform with that of the rest of my movies.

So like I asked above, would I hurt quality any by using a W-Zoom or H-Zoom value over 100%?

I'm wondering about a couple of things... Why not use 720 for the horizontal value? Personally I can see almost all artifacts of the encoding and don't want to lose any resolution, especially since I'm already destroying the shady areas and action of a film. My problem is that I can't get it to the standard NTSC res of 720x480, or the 720x540 that dvd burning programs use.

Gecko, how can you resize to fix the AR?

Last and foremost, WHY CAN'T YOU JUST ENCODE IN ORIGINAL RESOLUTION? Shouldn't the codec be designed to fit either 4:3 or 16:9?

It's pissing me off because I am making backups and I notice the 1.3% difference as well as the -0.8%. I know it may seem like 1.3% or -0.8% should be unnoticable but I can definitely tell the difference somehow. For some reason I can see compression artifacts much more than most of the people I know... and I wish everything was 60FPS instead of 24 or 30 (something that erased on a TV because of the interlace) because I can see that difference on my computer screen and some HDTV's.

My visual acuity has been tuned by playing games at 1600x1200 on a 19" monitor at 60FPS or higher. My audio acuity has been tuned by my father's $30,000 stereo system since birth.

I don't want to resize, I want to encode in the best settings for zero loss. Don't you wonder why there is no setting for 720x480, or 720x576 for PAL?

Because of the way mpeg4 encoding works, it is highly advisable to encode at dimensions that are exact multiples of 16. Depending on the codec, other dimensions will work, but you lose efficiency. (I don't know what techniques are used to enable arbitrary dimensions, but I guess it is just some form of padding). The colorspace YV12 requires the dimensions to be multiples of 2.

So there is your basic problem.

You can of course encode in the original resolution. The problems there are the black bars and that the AR will be quirky with most movies (of course you will also need a higher bitrate). You can fix the AR by doing anamorphic encodes with XviD for example an specifying the AR there. The decoder will then correctly resize upon playback.

Hope that helps.