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Old 17th May 2011, 14:00   #1  |  Link
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Resizing in avidemux

Ive been using gordian knot and autogk to encode dvds to avis for years and recently i began looking at avidemux. I was wondering how AutoGK determines how it resizes a video. autogk picks a resolution for you automatically and its different every time. In avidemux you have to specify it manually as far as i can tell. Is there some way to determine what would be the best resolution to resize a video to based on size, bitrate or something else?
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Old 17th May 2011, 16:21   #2  |  Link
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There is no such thing as a "best" resolution, except for the original video's "native" resolution!

Generally it is highly recommended to not resize at all. If you do resize, you should know why you need a resize. And then you also know what your target resolution is.

If you do not have a good reason to resize, then simply do not resize

Be aware: Some applications use "bits per pixel" (aka "bpp") as a metric to predict the quality of the re-encoded video.

So maybe (I don't know, I just speculate) AutoGK will lower the resolution based on the target average bitrate (target file size) until a certain minimum "bits per pixel" value has been reached.

It should be obvious that using "bits per pixel" as a quality indicator is complete nonsense, because it completely leaves out the "complexity" or "compressibility" of the individual video!

Having said that, in extreme cases, such as ultra-low bitrate encodes, it may indeed make sense to downsize the video prior to encoding. Generally that's not the case though.
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Last edited by LoRd_MuldeR; 17th May 2011 at 16:26.
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Old 18th May 2011, 14:49   #3  |  Link
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I didn't use AutoGK since 2007. but AFAIK it does compressability test using CQ2 to calculate resolution.
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