colormatrix question

[colinb]

Is it only necessary to use colormatrix() if you are calling a color conversion routine in AviSynth?

I'm currently using a script which takes DVD mpeg (via mpeg2source() ), crops and LanczosResize-es it the outputs to the HC encoder. I don't do any ConvertXXX() calls and the whole script stays in YV12 so can I forget about using colormatrix() ?

I guess the resize must have to interpolate the chroma values but can't it do this independently of whatever color matrix the source had.

[communist]

It is not for colorspace conversions but to 'correct' coefficients - read up here:
http://forum.doom9.org/showthread.php?s=&threadid=82217

[colinb]

OK, so it would seem that the DVD source will likely be using rec.709 (or one of the "nearly identical" matrices), and HC seems to assume rec.709.

In that case I would conclude that I do NOT need to use colormatrix().

To be absolutely sure I guess I could check the color matrix setting of the DVD source file, and in the unlikely event that it happened to be one of the rec.601 matrices then I would need to use

colormatrix("rec601->rec709")

[Wilbert]

To be absolutely sure I guess I could check the color matrix setting of the DVD source file, and in the unlikely event that it happened to be one of the rec.601 matrices then I would need to use

colormatrix("rec601->rec709")
Yes, and that can be checked with:

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

[Boulder]

And you could also use ColorMatrix(mode="rec.601->rec.709",d2v="path\clip.d2v") if you use an encoder which assumes rec.709 coeffs. The d2v parameter should point to the project file you load with MPEG2Source. In this way ColorMatrix is automatically applied if needed, if not, it only calls Limiter().

[danpos]

@Wilbert

I've readed the documentation out and I would like a additional clarification: My "The Day After Tomorrow" - R4 DVD presents SMPTE 170M colorimetry (DGIndex/DGDecode 1.4.5) and as I've understood:

1 - If I use CCE as encoder, I should use the line

colormatrix("Rec.601->Rec.709")

to provide the corrects coefficients to CCE. But

2 - If I use a libavcodec based encoder as AQE (AutoQmatEnc by SAPSTAR),

I shouldn't any colormatrix() statement in AVS script ?

TIA,

[Boulder]

Check the coefficients of a file you have encoded with a libavcodec based encoder with DGIndex. If it's the same as with CCE, you need the line there. Alternatively, use the d2v file as a reference to ColorMatrix as I wrote earlier.