Videos with high dynamic range (HDR) or wide color gamut (WICG) or otherwise not standard color types are not consistently supported in MediaWiki at this time.
- thumbnails usually appear gray/desaturated due to failure to convert the colorspace in ffmpeg creating a JPEG thumb
- transcoded video output may be forced to 8-bit, damaging 10-bit content
- transcoded video output may still retain the colorspace and hdr mastering markers but browser support is hit or miss and there's no attempt to check for support
Firefox, Chrome, and Safari all have different capabilities with HDR video playback, and may differ depending on operating system, hardware, etc.
Ideally, we should detect HDR and wide-gamut input and convert it to a bt709 SDR output, as well as a bt2020/pq HDR output; ffmpeg's zscale filter can map colors and tonemap and perform clipping or tone mapping.
There are some complications; current versions of ffmpeg don't handle smpte2084 (pq) transfer function in the colorspace filter, hence recommendation to use zscale. Additionally neither filter overrides HDR light level mastering metadata, so some files may require additional manipulation before they display correctly in some playback systems that take the light levels into account.
Example of an HDR video on Commons:
- Stream #0:0(eng): Video: vp9 (Profile 2), yuv420p10le(tv, unknown/bt2020/smpte2084), 3840x2160, SAR 1:1 DAR 16:9, 30 fps, 30 tbr, 1k tbn (default)
See also T19505 which asks for still image HDR support -- AVIF would be our primary target these days over on that end, and we should produce matching thumbnails if/when needed.