Change Aspect Ratio?

[Yo]

I use AutoGK (and have tried a couple other of the automated all-in-one DVD-DIVX programs) to create small videos to watch on my Pocket PC, with the resolution being the same as that of the full PPC screen, 320x240 (film rotated on the screen, of course). That is an aspect ration of 4:3.

When I have done this with video in 16:9 letterbox format, I don't like the result as much. I don't mind watching letterbox on the TV or on my computer screen, but the PPC screen is so small I would prefer the video to fill the screen, and not leave those black bars at the top and bottom.

Is there any way to change the aspect ratio of a 16:9 DVD to create a resulting AVI that is 4:3? Any setting in AutoGK? (If not, that would be a nice addition to the program.) (I guess that would probably involve some cropping at both sides. Is that what they do to change a letterbox movie to fit a standard TV screen, and not have the black bars?)

If not, is there a simple way to make that change afterwards, perhaps in VirtualDub or VirtualDubMod, or some other program?

I think I read in one of these posts about how someone did that by altering a .d2v file that was an intermediate step in the AutoGK process. I am still a newbie at this, and don't understand all the different processes and programs that AutoGK uses, I guess that's why I only have used such automated programs. Since AutoGK runs from start to finish automatically, I don't see how one could change an intermediate file sometime in the middle of processing.

Is there a simple way to do this?

[len0x]

There is no simple way to do it afterwards and AutoGK will probably never produce 4:3 output out of 16:9 input. Nothing stops you from using regular GK though...

[Yo]

Originally posted by len0x
There is no simple way to do it afterwards and AutoGK will probably never produce 4:3 output out of 16:9 input. Nothing stops you from using regular GK though...

One could do it with cropping and resizing in Vdub or vdubmod, no? But yes, not real simple--involves calculations, etc.

It seems it could be automated easily, no? Divide the height of the current video size by 3, and multiply by 4, to get what you want the width to be. Subtract that number from the current width. Divide the result by two, and crop each side by that amount. After cropping, resize to the size you want. It would save the user the trouble of going through the calculations, if a program had a checkbox "change aspect ratio 16:9 to 4:3", and did the cropping automatically.

I notice that the only choice for setting resolution in AutoGK is setting a fixed width--no setting to set height. Is that to keep the aspect ratio the same? (Since, when shown on a computer screen the video size (in pixels) is the same as the resolution--quite different than if it was shown on a TV screen, correct?) So that a user wouldn't mistakenly set a different aspect ratio (without cropping) and thereby distort the picture? Does the program always keep the aspect ratio exactly the same, when resizing to fit a fixed width? (Perhaps some kind of cropping capability would be nice to have at that stage, in case a user wants to do that.) (Better to do it beforehand than have to do it afterwards in another program, which I think would involve re-encoding, no?)

As far as me using the regular GordianKnot, I haven't tried it yet, but I'm still very new at this stuff, don't understand a lot of the terminology, I think it would probably be above my head at this point. Perhaps I'll try it one day.

[Yo]

Found a way to deal with this on the playing side.

I was playing the video created with AutoGK on my Pocket PC, with the new player program "Betaplayer". (A good new freeware player, BTW, for anyone who uses a Pocket PC. I think for Smartphones as well. Look at www.corecodec.com (http://www.corecodec.com) (not sure if .com or .org.), and you'll find it.

I saw under options, it had one called "Zoom". It was set to the default, "Fit Screen". That fit the length to the screen, leaving the two black bars at top and bottom. (320x240 screen, 320x176 video).

I tried another option--"Fit Height". That increased the size of the video so that the height filled the 240 pixel height of the screen, and made the length longer than the screen, which acted the same as if I cropped off the edges to make it fit. (Also a "Fit Width" option, but of course that would have been the same as "Fit Screen", in this case.)

Really a much better and simpler solution than cropping the video. One still has the full wide screen video, in case one wants to see it wide screen, and can zoom it to "fit height" in order for the movie to fill the small screen. A good thing for any PPC movie watcher to know! :)

I'm curious, how did AutoGK come up with the resolution of 320x176? I set the fixed width to 320 (hoping for 320x240), but I guess due to the 16:9 aspect ratio of the movie, it decreased the height to make 320x176. Taken strictly mathematically however, a 16:9 ratio starting with 320 would be 320:180. Why were four pixels taken off the 180 to make 176? How exactly is the height figured by AutoGK, when a fixed width is given?

Of course, when I switched the "Zoom" to "Fit Height", and the movie increased in size, so that the 176 pixel height of the video stretched to 240, that involves some degradation of the video quality. (It wasn't bad though.) But I'm thinking of perhaps encoding the movie again, and this time trying to get the height fixed at 240. (Which would of course, make the width longer than 320, to get the 9:16 aspect ratio.)

Unfortunately, there is no option in AutoGK to fix the height, only to fix the width. (Suggestion--this is something you might want to add. If you don't want to give the user the option to set both the width and the height, let them fix one or the other.)

So--I could try to estimate what the width should be, in order to make the width 240, and put in that number for the fixed width option. Figured out on a calculator what number should be the larger number in a 9:16 ratio, with the smaller number being 240, the larger number would be 426.666667. Well, of course I cannot set the width to that number! :p (And I'm not sure exactly how it's figured anyhow, since with the 320 width the height ended up at 176, rather than the mathematically accurate 180, in this case an even whole number.)

So, what number would I set the fixed width to, in order to end up with a fixed height of 240, in a video with the aspect ratio 16:9?

Thank you for your input. :)