That video doesn't look hdr, but more like an hdr video converted to rec709 without tonemapping
for example with hable tonemapping for 1000 nits
Code:
import vapoursynth as vs
core = vs.get_core()
c = core.lsmas.LibavSMASHSource(source= "C:/Users//Desktop/4kbs_trim.mp4")
c=core.resize.Bicubic(clip=c, format=vs.RGBS,filter_param_a=0.0,filter_param_b=0.75, range_in_s="limited", matrix_in_s="2020ncl", chromaloc_in_s="left", chromaloc_s="center", transfer_in_s="709", transfer_s="linear",dither_type="none")
#insert here tonemapping 1000nits
#exposure_bias=10
#tm = core.std.Expr(c, expr="x {exposure_bias} * 0.15 x {exposure_bias} * * 0.05 + * 0.004 + x {exposure_bias} * 0.15 x {exposure_bias} * * 0.50 + * 0.06 + / 0.02 0.30 / - ".format(exposure_bias=exposure_bias))
#w=((exposure_bias*(0.15*exposure_bias+0.10*0.50)+0.20*0.02)/(exposure_bias*(0.15*exposure_bias+0.50)+0.20*0.30))-0.02/0.30
#tm = core.std.Expr(clips=[tm,c], expr="x 1 {w} / * ".format(exposure_bias=exposure_bias,w=w))
c=core.resize.Bicubic(clip=c, format=vs.RGBS, transfer_in_s="linear", transfer_s="709",dither_type="none")
c=core.resize.Bicubic(clip=c, format=vs.YUV420P8, chromaloc_in_s="center", chromaloc_s="left", filter_param_a=0.0, filter_param_b=0.75, range_in_s="full", range_s="limited", matrix_s="709",dither_type="none")
c.set_output()
it gives me this
