#11541: All NVENC encoders change bt709 color space to bt470bg when pixel
format is
not specified
-------------------------------------+-------------------------------------
Reporter: fmnijk | Owner: (none)
Type: defect | Status: new
Priority: normal | Component: avcodec
Version: git-master | Resolution:
Keywords: colorspace | Blocked By:
NVENC scale |
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
-------------------------------------+-------------------------------------
Description changed by fmnijk:
Old description:
> 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 a "16bit" 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
New description:
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 a 16bit 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
Note: I have provided an example EXR file rendered with Unreal Engine 5 as
an attachment for reference and testing purposes.
## 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
--
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Ticket URL: <https://trac.ffmpeg.org/ticket/11541#comment:3>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker
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