[Feature]: Add Dolby Vision fallback and HDR-to-SDR tone mapping options

[sgill09]

Area (tag)

Playback

Problem statement

On some displays, especially macOS devices, Dolby Vision and HDR content can appear extremely dark or have incorrect brightness when the playback path does not handle the HDR metadata properly. This can make some newer movies and TV shows difficult or impossible to watch.
It would be useful to have built-in playback options that allow users to force a compatible SDR output when HDR or Dolby Vision playback is problematic.

Proposed solution

Add two optional playback settings:

1. Dolby Vision Fallback
   When enabled, ignore or strip Dolby Vision metadata/layers where possible and play the compatible HEVC base layer instead.
2. Force SDR / HDR Tone Mapping
   Tone-map HDR10 or Dolby Vision content to SDR/BT.709 while preserving correct brightness, contrast, and colours.
   These settings should be disabled by default so normal HDR/Dolby Vision playback remains unchanged for users whose systems support it correctly.
   Ideally, the options could appear under something like:
   Settings → Playback → HDR / Dolby Vision

Are you planning to implement this yourself?

Maybe, but only if approved first

Alternatives considered (optional)

No response

Additional context (optional)

No response