Cropping too much... even when disabled...

[MaxPowers]

Hi,

I used to use DVDx, but whilst searching for software for a difficult dvd to encode to Xvid (now I know because it's a hybrid, thanks to AutoGK :-),
I've tried AutoGK, but when I compare the cropping to the custom cropping I did with DVDx,
I noticed that it croppes a little too much at the X-coordinates (left & right)... see for yourself:

converted with AGK:
click to enlarge:
http://i25.tinypic.com/2s7i1yx.jpg (http://img235.imagevenue.com/img.php?image=08259_AGK_122_381lo.jpg)
720x416

converted with DVDx (720x576 - adjust output resolution to correct 4/3 gives 720x404):
click to enlarge:
http://i26.tinypic.com/2ro6txk.jpg (http://img225.imagevenue.com/img.php?image=08260_DVDx_122_443lo.jpg)
720x404

this one did not need any cropping, just the 16:9 aspect,

I've tried it with cropping disabled and automatic in AutoGK (no difference),

I'd also have a comment on the autocrop function, I think it would be better if autocrop was done further inside the video,
since many dvd's have intro's where the cropping is different than the actual main movie
(but I think it still does it correct if settings are unchanged, not sure),

is there a way to loose nothing of the movie by cropping?

I'm keeping the resolution fixed at 720, cause that's the resolution of all dvd's and
I don't see the point in reducing it to 640...

I also tried to manually crop, I used values derived from the custom manual cropping with DVDx,
but that did not do it correct either...

anyone?

thanks in advance for any help/info :-)

[yetanotherid]

I have a vague memory that DVDs can be either 720 or 704 pixels wide, but 704 are all that's displayed? But my understanding is that the correct resize for DVDs is 704 pixels wide.
Then there's the resizing factor.... from what I've worked out AutoGK always resizes width and height in multiples of 16, although I'm not exactly sure why. Usually resizing to either 720 or 704 will give you a height of 400 pixels, but I remember converting some episodic DVDs not long ago and every so often one would be 416 while most were 400. It's probably something to do with the fact that AutoGK crops the sides rather than the top and bottom to maintain aspect (as I understand it) so in order to resize correctly without cropping the top or bottom it might have needed to crop a bit more from the sides to give you 720.

One thing I've learned about AutoGK is that to me it seems very good at maintaining aspect, or keeping it as close as possible. By that I'm not referring to the aspect ratio in respect to the dimensions of the video, but the aspect of it's contents (if that makes sense). For example if you convert a DVD containing video of a circle, then the circle in the resulting AVI will still be as close to a circle as possible. So I guess depending on the aspect ratio of the source and the dimensions you choose to resize to, along with the length and width limitations, sometimes it crops a bit. That's much better than distorting the image in my opinion.

Which brings me to your two captures. It's a bit hard to tell, but to me it looks like one of them is a little distorted by being stretched in width, or the other is a little squashed in height. The question then would be, which one is closer to the original? If it's the one AutoGK produced, then I'd be grateful for the extra cropping.

I don't know how accurate any of the info in my post is. It's just what I've concluded from observations. Maybe someone who knows better will come along....

[BigDid]

Hi

...from what I've worked out AutoGK always resizes width and height in multiples of 16, although I'm not exactly sure why
If I recall correctly, for compatibility issues with external programs/filters used...

I missed the initial post, see How-to in tutorial:
- Sometimes auto crop used with default parameters by AutoGK cannot totally remove black bars or removes too much of a movie material. In this case "Tune auto crop parameters" is very handy. Threshold defines how sensitive auto crop will be: the higher the value the more cropping will be done. To completely disable audio crop you can set threshold to 0. "Number of frames to examine" is useful parameter to change if movie is a mixture of full screen/wide screen shots, so by selecting different frames that auto crop examines you can improve cropping process. "Starting frame" can help auto crop in situation when you have a full screen logo as a part of widescreen movie, in which case autocrop might decide that the whole source is full screen. By selecting a different starting frames you force auto crop not to examine irrelevant starting movie sequence. "Force cropping" option allows you to crop additional pixels after autocrop operation (if you find that you need to always crop several more pixels you can use this option). If you disable autocrop with threshold 0 then "force cropping" option becomes fully manual crop. Remember always to check how movie looks like after you set new auto crop parameters using Preview function of AutoGK

The last sentence => "using preview" will tell you if the resulting crop is screwed up and/or if, at least for preview, it works as intended.

Did

[yetanotherid]

Here's an experiment I tried today. Mainly because I've been trying to get my head around the whole aspect ratio thing myself. It's also one of the reasons I posted in this thread.

I took the same video, which has an aspect ratio of 2.35:1 and converted it twice. Once to 704 and then to 720. For the 704 conversion AutoGK game me a display aspect ratio of 2.32:1 (704x304) for the 720 conversion a display aspect ratio of 2.25:1 (720x320).

In order to determine what was cropped from the 720 conversion, I then loaded the videos into Media Player Classic. After a lot of fiddly resizing and moving I finally had the images the same size while one window sat in front of the other... so I could switch between each window and look to see if the shape of the objects (people's heads) appeared to be changing. As best as I could tell, within any resizing limitations MPC itself may have imposed, the shapes of objects within the image didn't change at all once I had the sizes matching.

It may be hard to put a visual on all that, and I couldn't capture the video itself in an image, but this one may help anyway. The window on top was the 720 conversion, with the one underneath being the 704 conversion, only that window was resized until the objects within the image lined up as far as size and shape goes. As you can see the 704 width video had to be enlarged noticeably more than 720 in order for the actual object size to match. Therefore, by resizing to 720 (the top window) rather than 704, the amount of cropping AutoGK was forced to do in order not to distort the original image is the amount by which the bottom window protrudes from from underneath the top one.

I hope I explained all that well enough for it to make sense. :-)

http://s5.tinypic.com/1xz1qd.jpg

For some reason the image wasn't loading with my post, although I think I fixed it.
But just to be sure:
http://s5.tinypic.com/1xz1qd.jpg

[manono]

converted with DVDx (720x576 - adjust output resolution to correct 4/3 gives 720x404):
AutoGK, quite correctly, resizes to Mod16. It sometimes crops into the active video in order to maintain the aspect ratio and keep the aspect error low. If you don't like how it crops and resizes, you can go into the Hidden Options and switch to ITU resizing to see if you like it any better.

[tamilan09]

You need to disable hardware acceleration to screenshot videos
Here's an experiment I tried today. Mainly because I've been trying to get my head around the whole aspect ratio thing myself. It's also one of the reasons I posted in this thread.

I took the same video, which has an aspect ratio of 2.35:1 and converted it twice. Once to 704 and then to 720. For the 704 conversion AutoGK game me a display aspect ratio of 2.32:1 (704x304) for the 720 conversion a display aspect ratio of 2.25:1 (720x320).

In order to determine what was cropped from the 720 conversion, I then loaded the videos into Media Player Classic. After a lot of fiddly resizing and moving I finally had the images the same size while one window sat in front of the other... so I could switch between each window and look to see if the shape of the objects (people's heads) appeared to be changing. As best as I could tell, within any resizing limitations MPC itself may have imposed, the shapes of objects within the image didn't change at all once I had the sizes matching.

It may be hard to put a visual on all that, and I couldn't capture the video itself in an image, but this one may help anyway. The window on top was the 720 conversion, with the one underneath being the 704 conversion, only that window was resized until the objects within the image lined up as far as size and shape goes. As you can see the 704 width video had to be enlarged noticeably more than 720 in order for the actual object size to match. Therefore, by resizing to 720 (the top window) rather than 704, the amount of cropping AutoGK was forced to do in order not to distort the original image is the amount by which the bottom window protrudes from from underneath the top one.

I hope I explained all that well enough for it to make sense. :-)

http://s5.tinypic.com/1xz1qd.jpg

For some reason the image wasn't loading with my post, although I think I fixed it.
But just to be sure:
http://s5.tinypic.com/1xz1qd.jpg