Different Color, Different Codec?

[Mooho Bae]

I’m not sure that here is the best forum for these questions…, anyway..

I have EX1, Premiere pro CS3, and the cineform NeoHD.
The CS3 can edit the mp4 file of EX1 directly, so I almost stopped using NeoHD after I bought CS3. However, recently, I found some curious things.

I compared two clips in CS3: One is the original MP4 file, and another is converted AVI file by using NeoHD. I guess these files look almost identical, bit I found the colors are slightly different.

So I compared color bar clip generated by EX1. Please examine attached screen capture images, they are composite video of the original MP4, Vector scope of the original MP4, composite video of the converted cineform AVI, and Vector scope of the converted cineform AVI, respectively.

The vector scope shows the difference clearly. Is it normal, or problematic? What makes this difference? Would anybody please reproduce these images?

Please comment on my questions.

MooHo.

[Swen Goebbels]

Some codecs work different at my knowledges.

I had in SD the same problems with my Canopus Codec. They used not only black, they used super black during capturing my videos... the Microsoft codec was different to this.

At all the Canopus Codec worked allways without any problems and I used it for years. Suddenly somebody request Colorbars and there I realized that black was not broadcast black.

[Marlon Martins]

this is a "classic" problems of wrong conversion of coefficients.

the mp4 version is doing a correct conversion (bt.709)

the cineform version is not (bt.601)

if you convert from bt.601 to bt.709 you will get the same colour.

if i remember, cineform has the options to specify the colorimetry of a file, in the options of the codec.

im not 100% sure, but HD shoud be bt.709 from begining to finish.

[Mooho Bae]

Thank you Swen and Marlon.

Marlon, More questions for you.
XDCAM-EX only supports HD video, so I guessed the color bar from it should be in bt. 709 color space.
And I used XDCAM-EX HQ 24P preset in the Premiere, so I guessed that the premire timeline and vector scope are already in bt. 709 color space.
If these two guesses are true, then I think the vector angle shoud point the marked position.
So, which guess of mine is wrong? please let me know..

[Marlon Martins]

Originally Posted by Mooho Bae

XDCAM-EX only supports HD video, so I guessed the color bar from it should be in bt. 709 color space.

the videos from EX1/3 have bt.709 coefficients, premiere works correctly with that. (i assume ;) )

the "problem" (that is not a problem) is probably in codec configuration.

when converting from YUY to RGB the codec uses the coefficients to do the correct color conversion, if it assume the wrong type (like bt.601) the colors get wrong.

cineform have the option to use bt.709, so is just a config problem.

i dont have premiere neither cineform (my computer is very old, do not have sse2)

also be sure if premiere have the option, to set vectorscope to "full levels" (not studio levels), as i whas testing some videos from this camera, and looks like it record in full levels, so the vectorscope can show wrong values.

vectorscope should be like this:

[David Newman]

CineForm is the correct output. Premiere's native mode gets most of the HD camera color-spaces wrong, as it is inherently 601 (SD only colorspace for YUV) and they never seems to do 601 to 709 conversion (I guess for speed concerns.) If you capture color bars from any of the HDV cameras as well, Premiere gets the color wrong. We are suprised that most users aren't upset by this (likely they are not aware,) because it would be another bonus for our business. We handle camera YUV in its native color space, then manage the color space through Premiere, although we do even more with Prospect HD over NEO HD, but both color decode the camera's 709 colorspace.

[Marlon Martins]

EWWWWWWWWWWW.. i was assuming premiere was the correct one... (so cineform was the bad one)

now that ive seen the vectorscopes of colorbars with cineform, i see. the cineform is the correct one...

sorry David to swap the guilty ;)

[Mooho Bae]

Thank you very much David and Marlon.

David, You halp me a lot. Now I restart to use NeoHD. But still there are some issues left for me. I need your halp more. Thanks again.

[Bill Ravens]

Not only that, but, if you do many multi-generational renders of your footage, Cineform will hold its values MUCH better than any interframe compression codec.