#11541: All NVENC encoders change bt709 color space to bt470bg when pixel
format is
not specified
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Reporter: fmnijk | Type: defect
Status: new | Priority: normal
Component: avcodec | Version: git-
Keywords: colorspace | master
NVENC scale | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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When using any NVENC encoder (av1_nvenc, hevc_nvenc, h264_nvenc) with
zscale or scale filter to set color space parameters, the color space gets
incorrectly set to bt470bg instead of bt709 when not explicitly specifying
a pixel format.
## Steps to reproduce:
1. Use an EXR file with linear transfer characteristics
2. Use zscale or scale to explicitly set matrix/color space to bt709
3. Encode with any NVENC encoder without specifying pixel format
## Expected behavior:
Output video should have color_space=bt709 as specified in the filter.
## Actual behavior:
Output video has color_space=bt470bg despite explicitly setting
matrix/color space to bt709.
## Problem examples:With zscale:
ffmpeg -i input_%04d.exr -vf "zscale=matrix=bt709:transfer=iec61966-2-1"
-c:v av1_nvenc output.mp4
With scale:
ffmpeg -i input_%04d.exr -vf
"scale=out_color_matrix=bt709:out_transfer=iec61966-2-1" -c:v av1_nvenc
output.mp4
Output properties for both cases:
"color_space": "bt470bg", # Should be bt709
"color_transfer": "iec61966-2-1"
## Working example (without NVENC):
ffmpeg -i input_%04d.exr -vf "zscale=matrix=bt709:transfer=iec61966-2-1"
output.mp4
Output properties:
"color_space": "bt709",
"color_transfer": "iec61966-2-1"
## Workarounds:
1. Adding any format filter to the chain fixes the issue:
ffmpeg -i input_%04d.exr -vf
"zscale=matrix=bt709:transfer=iec61966-2-1,format=yuv420p" -c:v av1_nvenc
output.mp4
2. Explicitly specifying pixel format as a parameter also works:
ffmpeg -i input_%04d.exr -vf "zscale=matrix=bt709:transfer=iec61966-2-1"
-pix_fmt yuv420p -c:v av1_nvenc output.mp4
Either way correctly outputs:
"color_space": "bt709",
"color_transfer": "iec61966-2-1"
## System Information:
ffmpeg version N-119165-gf3f1a48a07-20250407
OS: Windows 10 22H2
GPU: RTX 4090
NVIDIA Driver: NVIDIA Studio Driver 572.83
--
Ticket URL: <https://trac.ffmpeg.org/ticket/11541>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker
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