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Old 11 Mar 2003, 11:44 AM   #1
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Question Judging size and crop values when encoding (gordianknot), and question about ratio

heya,
i'm using gordianknot to make my .avs files, but i'm running into some complications. when i load an .avs file in virtualdub(mod) using avisynth 2.5 alpha and the MPEG2Dec3.dll plugin, it requires that:

* crop values are even
* video width are divisible by 4

this can lead to a some problems, and i have to manually fiddle around with the settings. are there any news of possible fixes to virtualdub to get around this, or does anyone have some good tips for fixing this? gordianknot sets uneven crop values often, and when i mess with them, the aspect ratio gets a bit off (0.1% perhaps in relation to 'smart crop all'.

another question is this: when i load an NTSC DVD in DVD2AVI, it says that it's 720x480 (1.5 ratio), but when i load the .d2v project in GK, the final aspect ratio will usually be around 1.42 for a 4:3 movie, or 2.33 for a 16:9 movie. is this supposed to be that way? is there something about the ways DVD are encoded and shown that i missed? when i play the specific 4:3 720:480 movie in my DVD player, the ratio is almost 1.2!

thanks for any help
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Old 11 Mar 2003, 12:55 PM   #2
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Default Re: Judging size and crop values when encoding (gordianknot), and question about rati

Quote:
Originally posted by Pilsner

i'm using gordianknot to make my .avs files, but i'm running into some complications. when i load an .avs file in virtualdub(mod) using avisynth 2.5 alpha and the MPEG2Dec3.dll plugin, it requires that:

* crop values are even
* video width are divisible by 4

this can lead to a some problems, and i have to manually fiddle around with the settings. are there any news of possible fixes to virtualdub to get around this, or does anyone have some good tips for fixing this?
This is almost cirtainly not virtualdub's fault or problem, and I doubt any modifications to virtualdub, will be able to fix it.

As for the crop values, that is almost cirtainly either the fault of avisynth or one of it's plugin. Are you doing any filtering between cropping and resizeing ?. I have never had any such problem, but I don't use avisynth 2.5, so that probably explains that.

As for the width, I'am not sure what might be the problem, but I'am pretty sure it's not virtualdub that is at fault. And using a width and height, that is at least divisible by 4 is strongly recommended for divx encoding anyway (it's required for divx5, I'am not sure about other versions)

Quote:
Originally posted by Pilsner

gordianknot sets uneven crop values often, and when i mess with them, the aspect ratio gets a bit off (0.1% perhaps in relation to 'smart crop all'.
You worry about a 0.1% AR error ?, I seriously doubt you would be able to spot a 3-4% error.

Quote:
Originally posted by Pilsner

another question is this: when i load an NTSC DVD in DVD2AVI, it says that it's 720x480 (1.5 ratio), but when i load the .d2v project in GK, the final aspect ratio will usually be around 1.42 for a 4:3 movie, or 2.33 for a 16:9 movie. is this supposed to be that way? is there something about the ways DVD are encoded and shown that i missed? when i play the specific 4:3 720:480 movie in my DVD player, the ratio is almost 1.2!
For DVD's resolution and AspectRatio is not tied together, because the pixels are not square. All DVD's are encoded either as 16:9 or 4:3, and the 720*480 is then stretched to fit this, durring playback.
If you don't crop the movie and set GordianKnot correctly to 4:3 or 16:9, you will get a 4:3 or 16:9 aspect ratio. But since most DVD's has some black borders around the edges, GordianKnot lets you crop some of this off while keeping the correct aspect ratio.
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Last edited by khp; 11 Mar 2003 at 12:58 PM
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Old 11 Mar 2003, 01:18 PM   #3
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Default Re: Re: Judging size and crop values when encoding (gordianknot), and question about rati

Quote:
Originally posted by khp
This is almost cirtainly not virtualdub's fault or problem, and I doubt any modifications to virtualdub, will be able to fix it.

As for the crop values, that is almost cirtainly either the fault of avisynth or one of it's plugin. Are you doing any filtering between cropping and resizeing ?. I have never had any such problem, but I don't use avisynth 2.5, so that probably explains that.
ok, what version of avisynth or program do you use then?

Quote:

For DVD's resolution and AspectRatio is not tied together, because the pixels are not square. All DVD's are encoded either as 16:9 or 4:3, and the 720*480 is then stretched to fit this, durring playback.
If you don't crop the movie and set GordianKnot correctly to 4:3 or 16:9, you will get a 4:3 or 16:9 aspect ratio. But since most DVD's has some black borders around the edges, GordianKnot lets you crop some of this off while keeping the correct aspect ratio.
*SMACKS HEAD*. duh, i had forgotten all about cropping removing the black bars
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Old 11 Mar 2003, 01:39 PM   #4
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Default Re: Re: Re: Judging size and crop values when encoding (gordianknot), and question ab

Quote:
Originally posted by Pilsner
ok, what version of avisynth or program do you use then?
I use avisynth 2.0.4. and 2.07.

Last edited by khp; 11 Mar 2003 at 01:44 PM
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Old 11 Mar 2003, 10:23 PM   #5
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Default

avisynth 2.5 works like a charm for me (and i love the speed increase it provides) and sticking to those div/4 rules is a must when using de-interlacers anyway.

i apply those settings for any given conversion and neither avisynth nor vdub/vdubMOD run into trouble.
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