[Bug]: Previews of HDR videos being generated are washed out (needs tonemap?) about server

[invario]

Have been researching the proper parameters to pass to FFMPEG to generate previews properly. Came across this link:
https://superuser.com/questions/1732301/convert-10bit-hdr-video-to-8bit-frames/1732304
It suggests that this parameter passed in would generate a proper preview/thumbnail for a HDR video. I tested it manually by generating a single frame and it appears to work. Interested in discussing this with anyone, thanks!
-vf zscale=t=linear:npl=100,format=gbrpf32le,zscale=p=bt709,tonemap=tonemap=hable:desat=0,zscale=t=bt709:m=bt709:r=tv,format=yuv420p

edit: AAAAAND, boom goes the dynamite. zscale isn't on every ffmpeg version so this won't work for everyone. Hmm...

edit2: Wow this is turning out to be more complicated than I thought. So FFMPEG needs zscale but not every FFMPEG is compiled with zscale enabled. Then, even with zscale, you can not use the same parameters for HDR source video as you would for SDR source video because if you do, the resultant image/preview file is very, very dark and generated wrong. So in order to properly do this, the source video must be read, and then if, and only if it is HDR should the proper parameters get added to the command line for FFMPEG. Maybe a config.php parameters needs to be added to indicate if the FFMPEG installation has zscale available, otherwise default to no?