Staxrip Image Output Mod: What does it affect?

[rgDino]

Other than allowing me to encode at resolutions divisible by 2, 4, 8, 16, etc., what does changing the image output mod affect?

Does it make processing a video faster? Does it affect image quality? Are some mod numbers better choices for certain programs that hook into Staxrip (any of the video tools that Staxrip calls upon)?

[jagabo]

Other than allowing me to encode at resolutions divisible by 2, 4, 8, 16, etc., what does changing the image output mod affect?

It limits frame sizes to integer multiples of 2, 4, 8, 16, etc. Some codecs don't work with odd frame sizes, mod 2, etc. Also, some playback devices don't work with odd, or mod 2, etc. Interlaced video usually needs to be mod 4 or higher. You should select the lowest mod supported by both your codec and all your intended playback devices. Mod 4 is safe for most modern codecs and devices. Some old codecs and devices required mod 16.

Does it make processing a video faster?

Not significantly.

Does it affect image quality?

Not significantly.

[Selur]

rough explanation:
mod2 <- is always needed when 4:2:0 color sampling is used
mod4 <- is needed when interlaced + 4:2:0 color sampling is used
mod16 often gives the most speed gain since macroblocks that make up an image are often 16x16
mod8 often is a first try to get 16x16 macroblock codecs to support more resolutions
That said, with modern codecs the modX choice shouldn't make much of a difference as long as the mod satisfies the color sampling (+ interlaced) restriction, since modern codecs are often optimized to handle the appropriate resolution for the chosen color sampling with much of a consequence in regard of speed and quality.

-> I agree with jagabo, mod4 should be a save choice for not too old codecs and hardware