megui adds colormatrix avs plugin by default

[codemaster]

This is an avs script generated by megui avs script creator:

LoadPlugin("D:\InstalledApps\MeGUI\tools\dgindex\DGDecode.dll")
DGDecode_mpeg2source("E:\source\disc2\VIDEO_TS\VTS_01_1.d2v", info=3)
LoadPlugin("D:\InstalledApps\MeGUI\tools\avisynth_plugin\ColorMatrix.dll")
ColorMatrix(hints=true, interlaced=true, threads=0)
Load_Stdcall_Plugin("D:\InstalledApps\MeGUI\tools\yadif\yadif.dll")
Yadif(order=1)
crop(14, 4, -10, -4)
LanczosResize(688,514) # Lanczos (Sharp)

By default, megui included the ColorMatrix plugin. Why is this plugin or filter included by default ? What does the parameter "hints=true" represent ?

[Selur]

What does the parameter "hints=true" represent ?

hints (default false)
DGDecode v1.20 and newer versions output colorimetry hints in the video. The colorimetry info (see Colorimetry) can be viewed using

Mpeg2source("F:\TestStreams\avs\AguileraGrammies.d2v", info=1)

The hints are used when setting info=3 in Mpeg2source, setting hints = true in ColorMatrix and when using ColorMatrix directly after loading the video

Mpeg2source("F:\TestStreams\avs\AguileraGrammies.d2v", info=3)
ColorMatrix(hints=true)

When hints are not passed through (for examle because you are using a wrong dvd2avi/dgdecode version) it will output an error.
Technically (although I've never seen such streams) the colorimetry info can be different throughout your video, the hints option will handle this correctly.

see: http://avisynth.org.ru/docs/english/externalfilters/colormatrix.htm

Why is this plugin or filter included by default ?

Because whoever wrote the code responsible for it things it's a good idea to do so.
(probably because a bunch of people complained about mismatching colours)

[hello_hello]

It's generally pointless and goes back to the days when people thought DVD video used R.709 for decoding YUV video to RGB (on playback) rather than R.601. The two are slightly different "formulas" for converting YUV video to RGB. Standard definition video pretty much always uses R.601 while HD always uses R.709. So the idea was if a DVD video happened to use R.709, the colormatrix plugin would convert it to R.601 while encoding, which would result in the encoded video displaying correctly.

After the video has been indexed, DGDecode reports the colorimetry used. The "hint"s parameter tells colormatrix to use the information supplied by DGDecode, and then convert from R.709 to R.601 if necessary. If the video is already R.601 (which all DVD video will be) then no conversion takes place... hence colormatrix being used the way it is being very pointless.

I've disabled it myself (it's only added to the script for DVD or mpeg2 video) and I've suggested to one of the MeGUI developers they should just get rid of it completely, but so far they haven't. If you happen to be converting HD mpeg2 video, always disable it in the AVS Script Creator (you can use the AVS Profile configuration to disable it by default) as it can potentially convert the colours when it shouldn't, but for SD definition it doesn't really matter. It won't do anything.