[FFmpeg-devel] Native jpeg2000 encoder produces random color artifacts with 12-bit YUV422P12 HDR content

[FFmpeg-devel] Native jpeg2000 encoder produces random color artifacts with 12-bit YUV422P12 HDR content

[Domenico Del Monaco via ffmpeg-devel]

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## Description
The native `jpeg2000` encoder produces random green/red pixel artifacts 
when encoding 12-bit YUV422P12 HDR content via AviSynth input.

The issue is reproducible regardless of:
- dithering settings (error_diffusion, ordered, none)
- q:v parameter (with or without)
- FFmpeg limiter filter

The same pipeline using `libopenjpeg` produces correct output with no 
artifacts.

## Command that produces artifacts
ffmpeg -i input.avs -c:v jpeg2000 -q:v 1 -pix_fmt yuv422p12le 
-colorspace bt2020nc -color_trc smpte2084 -color_primaries bt2020 
-color_range limited -y -f mxf output.mxf

## Command that works correctly
ffmpeg -i input.avs -c:v libopenjpeg -compression_level 6 -pix_fmt 
yuv422p12le -colorspace bt2020nc -color_trc smpte2084 -color_primaries 
bt2020 -color_range limited -y -f mxf output.mxf

## Input pipeline
AviSynth script with Dolby Vision FEL content processed via DoViBaker 
plugin.
Output is RGB converted to YUV422P12 via z_ConvertFormat:
colorspace_op="rgb:st2084:2020:full=>2020ncl:st2084:2020:limited"
dither_type="error_diffusion"

## Expected behavior
Clean 12-bit output identical to libopenjpeg output.

## Actual behavior
Random green/red pixel artifacts scattered randomly across frames.
Artifacts are visible in DaVinci Resolve and media players.
Artifacts change position randomly between frames.

## FFmpeg version 8.01

I am attaching an image of the bug detected.

Thank you

Domenico





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