Doom9's Forum - View Single Post - Gamma-aware, dithered colorspace conversion and resizing

Sapo84 · 26th December 2011, 22:53

This is probably is a bug report.

I was evaluating various resize methods with an anime source.

Dither_y_gamma_to_linear()
Dither_resize16(1280, 720)
Dither_y_linear_to_gamma()
http://img37.imageshack.us/img37/7812/mawarugamma1.png

ResampleHQ(1280,720,srcmatrix="TV.709",dstmatrix="TV.709",dstcolorspace="YV12",kernel="SPLINE36")
http://img851.imageshack.us/img851/4...warugamma3.png

Spline36Resize(1280,720)
http://img832.imageshack.us/img832/6...warugamma4.png

The PNGs are taken with AvsPmod (Rec.709 matrix).

The luma plane is correct with dither_resize16 and ResampleHQ, which is what I expected.
The chroma planes, instead, look very different with ResampleHQ, the reds are much "darker".

http://img42.imageshack.us/img42/69/mawarugamma5.png
The source frame.

Moreover if we convert to RGB and then resize with ResampleHQ (just use the last png as source, if you want to test), the result is again very different.
http://img42.imageshack.us/img42/6609/mawarugamma6.png

I think there is a bug in how ResampleHQ handles chroma in YV12 mode.

26th December 2011, 22:53	#186 \| Link
Sapo84 Registered User Join Date: May 2008 Posts: 40	This is probably is a bug report. I was evaluating various resize methods with an anime source. Dither_y_gamma_to_linear() Dither_resize16(1280, 720) Dither_y_linear_to_gamma() http://img37.imageshack.us/img37/7812/mawarugamma1.png ResampleHQ(1280,720,srcmatrix="TV.709",dstmatrix="TV.709",dstcolorspace="YV12",kernel="SPLINE36") http://img851.imageshack.us/img851/4...warugamma3.png Spline36Resize(1280,720) http://img832.imageshack.us/img832/6...warugamma4.png The PNGs are taken with AvsPmod (Rec.709 matrix). The luma plane is correct with dither_resize16 and ResampleHQ, which is what I expected. The chroma planes, instead, look very different with ResampleHQ, the reds are much "darker". http://img42.imageshack.us/img42/69/mawarugamma5.png The source frame. Moreover if we convert to RGB and then resize with ResampleHQ (just use the last png as source, if you want to test), the result is again very different. http://img42.imageshack.us/img42/6609/mawarugamma6.png I think there is a bug in how ResampleHQ handles chroma in YV12 mode. Last edited by Sapo84; 26th December 2011 at 22:56.