Hardware Downscaler: UHD HLG to FULL HD SDR

[FranceBB]

Hi,
I'm looking for an hardware Downscaler.
The streams I'm trying to get from the satellite have the following specs.

Input:
Codec: HEVC H.265
Resolution: 3840x2160 UHD
Bitrate: 25 Mbit/s
Frame rate: 50fps progressive
Color space: 4:2:0 planar (I don't know whether they are type1 or type2)
Type: Limited TV Range 64-940
Color Curve: HLG
Color matrix: BT2020nc HDR
Bit depth: 10bit planar
Nits: 1000

I don't know the level of the encoded HEVC stream, but I don't think it matters.

Desired output:
Resolution: 1920x1080 FULL HD
Frame rate: 50fps progressive
Color Space: 4:2:0 planar (yv12)
Type: Limited TV Range 16-235
Color matrix: BT709 SDR
Bit depth: 8bit planar

I would like the hardware Downscaler to take that signal from the decoder in input via HDMI and to output a signal with the "desired output" specifications via HDMI. Audio input is gonna be Dolby Surround 5.1 AC3 384 kbit/s 48'000Hz and I'd like it to be passed through HDMI as it is.

I was looking at products online on eBay and I found a few of them, but none of them says anything about bit depth, nits, color curve and so on, so not only I don't know whether what I wanna do is supported or not, but I don't even know which resizing kernel is gonna be used, whether 10bit is gonna be truncated to 8bit or a dithering algorithm is applied and so on, which worries me a bit...

For instance, will something like this do what I want?
https://www.ebay.com/itm/Ultra-HDMI-4K-1080p-Video-Scaler-With-HDMI-Pass-Through/323226081347?hash=item4b41c69843:g:A2YAAOSwdjha6P2c

[Blue_MiSfit]

AFAIK, one of the whole points of HLG is that it looks okay on SDR displays without any conversion. However, you'd still need to do the colorspace conversion from 2020 to 709. I don't think you'll find anything cheap that can do this. Your ebay scaler definitely won't.

https://www.aja.com/products/fs-hdr

This will absolutely do it, but it's $8k. ;)

Maybe you can find a cheaper LUT box that can do this job.

I also think MadVR should be able to do this for realtime playback on a Windows PC as long as you have a good GPU. Ask here: https://forum.doom9.org/showthread.php?t=146228

[FranceBB]

Well, yes, HLG can be displayed on both HDR and SDR displays, so it shouldn't be so hard to go from BT2020 SDR to BT709 SDR, is it? At least, it should be easier than tonemapping a PQ source.
I do have a few professional hardware converter at work in which I can use my LUTs and so on but I don't want something professional that works in SDI, I just want something that downscales for personal home use. After all, MPV does it, Potplayer does it, MPC-HC with MadVR does it, why can't a powerful enough yet cheap hardware converter do it?

[Asmodian]

I wonder if Envy (https://mailchi.mp/c7615e96b103/28ktk2x74t/) will be able to accomplish this?

If tone mapping HDR one can see how downscaling to 1080p could be useful at the same time.

[Blue_MiSfit]

I'm sure a cheap FPGA could totally do this in real-time, but it's a very specific use case and I don't know if anyone has made a product for it :)

[kolak]

Those cheap boxes won't do it well most likely. HLG meant to look good on SDR display? This is more theory than practice. You still need to do some correction (on top of gamut conversion) as it looks very dull and lifeless. BBC has some LUTs for it, so maybe look for a box wich supports LUT processing. Otherwise you need a proper box from AJA or other company (eg. ex Snell, now GrassValley). There is this: https://www.studiodaily.com/2019/04/lynx-technik-says-hdr-evie-better-live-hdrsdr-converter/ or maybe this cheap HDFury box: https://www.hdfury.eu/hdfurydiva.html
On software side you can always do it easily and reliably for free with eg. Resolve.

AJA box uses ColorFront's conversion engine, which is probably one of the best out there (http://www.colorfront.com/index.php?page=COLORFRONT%20ENGINE)

[Blue_MiSfit]

Great advice ^^

[FranceBB]

you need a proper box from AJA or other company (eg. ex Snell, now GrassValley). There is this: https://www.studiodaily.com/2019/04/lynx-technik-says-hdr-evie-better-live-hdrsdr-converter/ or maybe this cheap HDFury box: https://www.hdfury.eu/hdfurydiva.html

AJA box uses ColorFront's conversion engine, which is probably one of the best out there (http://www.colorfront.com/index.php?page=COLORFRONT%20ENGINE)

Thanks! That's exactly what I was looking for!