auto gk resolution

[Daedalus01]

Hi,

when encoding a movie autogk (under both AUTO and MAX WIDTH resolution settings) will encode my movie (dragon squad) at 608x352 when the DVD itself is 720x480

is it just cropping the black borders? or am i missing some video?

EDIT: ok i read a tut on auto gk and i should use MIN WIDTH instead. However i stil got 1 q. Do i lose a lot of qualtiy by reducing resulution as opposed to forcing a minimuim width of 720? i am encoding 2 CDS with AC3, so would a reduction in quality% be significant?

[CWR03]

Do i lose a lot of qualtiy by reducing resulution as opposed to forcing a minimuim width of 720?
It depends on what you refer to as "quality." As you reduce the resolution, you'll begin to lose detail. If you keep the same bitrate with a larger resolution you'll introduce artifacts into the video.
i am encoding 2 CDS with AC3, so would a reduction in quality% be significant?
It's entirely dependent on your perception - the only way to really tell is to try and see how good (or bad) it looks, then take notes of what settings you used for your next attempt.

[jggimi]

All commercial NTSC DVDs have a fixed resolution of 720x480 (PAL is 720x576).

But this resolution is neither 4:3 nor 16:9. That is because DVDs do not have square pixels. They have two different shapes, depending on the DVD's Display Aspect Ratio (DAR). Your TV shape, the DAR, and the letterboxing will restore the image to the proper aspect ratio for display.

Standard AVI files have square pixels, just like your PC monitor. And standalone players know this.

Therefore, a standard conversion to AVI will require resizing, and usually, letterboxing is stripped away as it is unnecessary in AVI videos.

608x352 is 1.73:1 in square pixels, so I assume you're dealing with the 2005 release with that title, rather than the 1974 release. www.imdb.com has specs for the latter, which was 2.35:1.

[Daedalus01]

All commercial NTSC DVDs have a fixed resolution of 720x480 (PAL is 720x576).

But this resolution is neither 4:3 nor 16:9. That is because DVDs do not have square pixels. They have two different shapes, depending on the DVD's Display Aspect Ratio (DAR). Your TV shape, the DAR, and the letterboxing will restore the image to the proper aspect ratio for display.

Standard AVI files have square pixels, just like your PC monitor. And standalone players know this.

Therefore, a standard conversion to AVI will require resizing, and usually, letterboxing is stripped away as it is unnecessary in AVI videos.

608x352 is 1.73:1 in square pixels, so I assume you're dealing with the 2005 release with that title, rather than the 1974 release. www.imdb.com has specs for the latter, which was 2.35:1.

hi, thanks for your reply. so wat would happen if i forced a 720width?

[jggimi]

AutoGK will use the closest size it can get to, using modulo 16, if I remember correctly. 720x416, 720x400, 720x432 ... If mod 32 is used, obviously there will be less options for resizing. 720 is mod16, but not mod32. :)

[Daedalus01]

no but wat i meant was wat wld happen if i forced the square pixel aspect ratio? would the aspect ratio be wrong when playing on a monitor? Are there any quality gains?

[CWR03]

You can force whatever you like, and as long as you plan to play it on your PC you may not notice any adverse effects, but they'll likely be incompatible with a standalone player, and you may not be able to change the DAR to correct it. There would be no gain in quality.

Forcing a 720 width of a 4:3 video will mean stretching the height - you can't gain quality by just adding height to it. All you'll get is either a poor quality video or a larger file.

[jggimi]

I don't think you understand what I wrote above. Let me try again.

DVDs do not have square pixels. Your PC monitor does. In order to play a DVD on a PC correctly, the video image MUST be resized at some point. By resizing, I'm talking about change the shape of the rectangle, not zooming.

A Software DVD player on your PC resizes the video, on playback, into square pixels. A standard AVI file made from that DVD will have been resized into square pixels before encoding.

Now, as I mentioned above, and again here, an AVI file is designed to be played back on a PC's monitor, with square pixels.

With me, still? Two more points, then I'll give up.

1) If you want to convert a DVD video stream into an AVI file, the most common practice is to resize the video stream so that it uses square pixels. AutoGK does this, as does most every other DVD -> AVI encoding toolset. AutoGK does this automatically; you have some control over width selection. If you depart from automatic width, you may end up with a result that does not have the peak image quality possible with the tool. By limiting AutoGK's width selection, you limit the software's capability to manage the image quality for you.

2) If you wish to encode DVD video with no resizing, you can do so, but not with AutoGK. And playback will require a software AVI player that can resize to the appropriate aspect ratio: 4:3 or 16:9. Most can, but not all of them.

I keep using the term "standard AVI" as It is possible to add aspect ratio signalling to an AVI file -- a DAR, if you like -- but that is outside the scope of AutoGK discussion, and requires both special software and some unique software players to enable the capability..

As to image quality and "should I resize or not before encoding" -- there is the possibility that an unresized encoding may produce a higher perceived quality when resized upon playback, compared to an already resized video. But there are many factors that affect perceived quality, and a lower resolution video may look better to the human eye and brain, even when zoomed to fill your monitor's display. You can run multiple encodings of content "A" and get one result, then run multiple encodings of content "B" and get completely different results.

In stead of fretting about possible results, why not try a few encodings and see for yourself? You'll learn something, I'm sure. :)