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Re: avi writing ? (xsize) [message #40017 is a reply to message #40010]

Tue, 06 July 2004 15:33

Mark Hadfield
Messages: 783
Registered: May 1995

Senior Member

R.G. Stockwell wrote:
> "Mark Hadfield" <m.hadfield@niwa.co.nz> wrote in message news:cc9t5r$2vg$1@newsreader.mailgate.org...
>
>> R.G. Stockwell wrote:
>
> ...
>
>>> What are the valid xsizes for building AVIs?
>>
>> It depends on the codec. Many require that both dimensions be multiples
>> of 2, some require multiples of 4. The latter works for all codecs I
>> have tried (and I have tried quite a few).
>>
>>
>> --
>> Mark Hadfield "Ka puwaha te tai nei, Hoea tatou"
>> m.hadfield@niwa.co.nz
>> National Institute for Water and Atmospheric Research (NIWA)
>
>
> Thanks Mark,
> i'll run some code to verify the factor of 4 in size, and it
> should be easy enough to code around. After I had seen that
> it was not a factor of 2 that was the problem, I hadn't thought
> that 4 would be the factor. I was guessing that is only came in
> typical screen sizes or something like that.

I believe it's mostly to do with the requirements of the compression
algorithm. These algorithms use mathematical techniques like discrete
cosine transform that tend to work in blocks of 2^n, where n is some
small integer.

You can see the requirements of each of the codecs installed on your
system with VirtualDub, a free AVI-writing program:

http://www.virtualdub.org/

Go to the "Select video compression" dialogue and scroll through.

After writing the reply above, I did just this and noticed that one of
the codecs that I've installed requires the width and height to be
multiples of 8. But the codec in question (ASLC) probably isn't on your
system. The one you're most likely to have trouble with is DivX, for
which width must be a multiple of 4 and height a multiple of 2.

--
Mark Hadfield "Ka puwaha te tai nei, Hoea tatou"
m.hadfield@niwa.co.nz
National Institute for Water and Atmospheric Research (NIWA)

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[Message index]

		Re: avi writing ? (xsize) By: David Fanning on Wed, 07 July 2004 08:33
		Re: avi writing ? (xsize) By: Haje Korth on Wed, 07 July 2004 07:56
		Re: avi writing ? (xsize) By: Mark Hadfield on Tue, 06 July 2004 15:33
		Re: avi writing ? (xsize) By: R.G. Stockwell on Tue, 06 July 2004 09:09
		Re: avi writing ? (xsize) By: Mark Hadfield on Sun, 04 July 2004 14:34
		Re: avi writing ? (xsize) By: R.G. Stockwell on Sat, 10 July 2004 12:49
		Re: avi writing ? (xsize) By: Haje Korth on Wed, 07 July 2004 13:20

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