@Cary Knoop... of course, making Rec.709 in PQ won't make it look better; what I needed was different. I had mixed sources: a legacy SDR with Rec709 and an HDR with Rec2020 PQ.
I needed to encode them together in a single video file as Rec2020 PQ, so I had to scale the SDR Rec709 parts to be displayed correctly in Rec2020 color space using the PQ curve.
This way, they are gonna look exactly identical to the original Rec.709 SDR file, but they will be encoded in a Rec2020 PQ file.
In other words, I can encode the scenes of the journalist interviewing the player (real HDR Rec2020 PQ), and the footages of the old games that were in SDR Rec709 all together in Rec2020 PQ.
Scaling them is not gonna add any additional information, but the "goal" is to encode legacy contents together with new contents in an HDR Rec2020 PQ file.
