[FFmpeg-user] decoding jpeg2000 problem

[Carles Vila]

Hi,
Resurrecting semi-old thread. Hope it's OK.

I've been struggling a long time to get the best possible conversion from
DCinema with ffmpeg. No matter what I try I always get weird color
artifacts at low levels, which I can best describe as "posterization".
I know it must be possible because a commercial software (easyDCP) exports
ProRes files which are fine.

I'd like to help in determining where exactly the problem lies, if it's the
JPEG2000 decoder, the color conversion matrix, bit depth reduction or
whatever, but I don't have the knowledge about the innards of ffmpeg to be
able to determine that.
Let me know if I can produce test patterns or run specific commands to
visualize the problem or narrow down the possible cause.
Thank you!!
PS: you can see command line and console output earlier in this thread.




On 4 September 2015 at 23:23, Marcelo Boufleur <mboufleur at gmail.com> wrote:

> >
> > Iirc, ImageMagick does not support xyz, so this is always
> > broken.
>
>
> ImageMagick does support xyz. The correct commad line for XYZ to RGB
> conversion can be found here
> <http://www.imagemagick.org/discourse-server/viewtopic.php?t=26953>.
>
> I always felt that previous versions of FFmpeg missed the Normalization
> Factor for White Point in DCinema (Luminance level 48fL for a Peak of 52.37
> cd/m2), not sure about the latest versions.
>
> Also, whenever I attempted to convert MXF DCinema files with XYZ colorspace
> into Quicktime ProRes, I always had to apply "colormatrix=bt601:bt709" to
> get proper conversion.
>
> Again, this had to be done for previous versions of FFmpeg; and after the
> colormatrix conversion, final ProRes would still miss the normalization
> Factor.
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