[Bug] Thumbnails look wrong for HDR videos

[Igetin]

Description

I use ffmpegthumbnailer as the video thumbnailer on my Fedora system, and I usually view those thumbnails via Nautilus. I noticed the thumbnails look wrong for HDR videos (at least for dvhe.05.03 and dvhe.08.03/HDR10 videos).

Steps to Reproduce

Test files:

• dvhe.05.03.mp4
• dvhe.08.03-HDR10-compatible.mp4

ffmpegthumbnailer -t 00:00:00 -s 0 \
    -i dvhe.05.03.mp4 \
    -o dvhe.05.03.thumbnail.jpeg

ffmpegthumbnailer -t 00:00:00 -s 0 \
    -i dvhe.08.03-HDR10-compatible.mp4 \
    -o dvhe.08.03-HDR10-compatible.thumbnail.jpeg

Expected Behavior

Thumbnails for HDR videos should show the correct colors.

Actual Behavior

The thumbnails either look too dark (dvhe.08.03) or have a heavy green & purple tint (dvhe.05.03). The problem occurs on both the JPEG and PNG output formats.

Thumbnail Comparison Table

dvhe.05.03.mp4

ffmpegthumbnailer	mpv screenshot (how it should look like)

dvhe.08.03-HDR10-compatible.mp4

ffmpegthumbnailer	mpv screenshot (how it should look like)

Software information

• OS: Fedora 40
• fmpegthumbnailer version: 2.2.3 (tested both on the RPM available on RPM Fusion and a self-built binary)