So, to me the most obvious thing about this clip is just how
little tone mapping is actually happening here. I mean, have a look at this screenshot:
This is the output of conversion to SDR BT.709 via libplacebo. Tone-mapping is completely disabled (the cyan regions show areas where the source shadow detail falls below the 1000:1 contrast black floor target), so it does not influence anything here. Gamut-mapping is replaced by a no-op which simply highlights out-of-gamut pixels and leaves in-gamut pixels completely untouched.
So, for areas of this image which are "preserved" (not clipped) this is basically a direct conversion from the HDR BT.2020 source to the SDR BT.709 target. This is the skin tone
exactly as it would appear on a HDR/BT.2020 reference monitor, for those parts of the image. So it represents a
definitive baseline for artistic intent. Any deviation from this by the tone/gamut mapper is a perceptual distortion of the image.
Attached below this is a version of the same output configuration (BT.709 SDR) but with libplacebo default tone/gamut mapping settings in use (which, for this clip, consults HDR10+ metadata for tone-mapping), and finally, a version that ignores HDR10+ metadata and uses only our own built-in HDR scene evaluation and dynamic tone-mapping (spline). (Note for the curious: the reason spline is so much brighter here is because I am running it on only the single exported frame, which does not contain any bright highlights, whereas the dynamic HDR10+ metadata is calculated for the whole scene. In a fair comparison, this would be less of a factor, so take the brighter image with a grain of salt)
So, what's the take-away here? It seems obvious to me that libplacebo's tone-mapping is
exactly on the money with respect to what the shot is supposed to look like in HDR. It may not subjectively reproduce that SDR "hollywood graded" feel that madVR apparently produces, but personally, I think it's rather silly to introduce such extreme aesthetic choices into what should be an as-objective-as-possible piece of software. If anything, libplacebo gives you the tools to recreate any such distortion yourself if you want to, by doing all tone/gamut mapping in a perceptually uniform color space.