Relative pros and cons of Overlay() and mt_merge()

[fvisagie]

To an Avisynth novice like me it appears that Overlay() and mt_merge() do much the same job.

But I'm sure they both exist for a reason. What are their relative strengths and weaknesses and when is it better to use which?

Thanks in advance,
Francois

[Didée]

Overlay is a filter of the Avisynth core. Mt_merge is an external plugin from MaskTools.

Briefly:
- mt_merge is exclusively for YV12 video, YUY2 can be done only with additional tricks, RGB is not supported at all. It is fast. It is easy to use.

- Overlay is very versatile, working with any colorspace, even mixed colorspaces between input clips. It is slow. It has lots of parameters, lots of options, lots of operating modes. It is rather easy to make something wrong, perhaps without even noticing it.

(Personal) recommendation: use mt_merge whenever possible. Use Overlay in cases that are not supported by mt_merge.

[fvisagie]

Thanks, Didée, your response is most appreciated.

[Gavino]

To add to Didée's excellent summary, don't forget that Layer (http://avisynth.org/mediawiki/Layer)() provides a more efficient alternative to Overlay() for RGB and YUY2 clips, especially useful for RGB32 where it uses the alpha channel as a mask.

[fvisagie]

Thanks, Gavino :).