Using SDR clips in HDR project: Working, but have to render SDR twice?

Teagan wrote on 4/20/2021, 4:31 PM

Hi, I have things working but I'm very confused why it is working and why it makes me have to render the rec 709 clip in the HDR project settings, separately, and then put it back in the original project with the HDR files and then render it out again to have the luminance values make sense.

Ok, to back up a bit, I have only one HDR camera at the moment and I am using an SDR camera as well, so I thought why can't I just mix them both and have the HDR part of the video go above 100 nits while the SDR part caps at 100 nits and have the best of both worlds?

I first put the HDR clips (HLG rec.2020 1000 nits) and the SDR clips (rec.709) in one timeline with the HDR10 preset with Rec.2020 ST2084 1000 Nits as the view transform. What comes out is the SDR clip's luminance values are way too high, as I expected, and they go way up to about 600-800 nits and are way too bright on my HDR TV that I'm using to grade.

The next part is the odd part: I thought I'd render the SDR clip through this project settings, like a proxy, and then put it back in the first project so there's not mixing input color spaces and, to my amazement, the SDR portion maxes at 100 nits while preserving color information correctly. The HDR part goes above 100 nits to around 250 which is correct for the room I recorded both the clips in.

My question is why do I have to render the rec.709 clip twice and how can I save time by rendering the project once?

Here's one frame's luminance values from the project that I just rendered once, from the SDR part: (too bright for SDR)

And here is the same frame but rendered basically twice: I put it through the project settings for the project once and then put that rendered file back into the first project and it looks fine, colors are good, but it's not just not 600 nits like the first time: (looks just like an SDR video is on the screen, while the HDR10 flag is active on the TV)

Why is this working and how can I avoid having to render the SDR clip twice? Something about a view transform applying twice? Is it tonemapping? I have no idea but it's working for me but I have to render twice.

Comments

Yelandkeil wrote on 4/20/2021, 5:22 PM

1, take a little bit time to read my text (and give a thankme😜):
The Way2dig Video Colorspaces in Vegaspro18-ACES

2, I assume you have an HDR-Monitor as editing workspace and an HDR-TV as second preview display.
There's somebody already experienced similar situation and successfully, as he reported, edited with this setting:

3, after the project has been set properly, turn on the HDR-button for preview-window in Vegaspro. And drop your source material onto timeline.

3.1, a native HDR/HLG clip will be recognized by Vegaspro automatically, if not, do it manually.
3.2, the other clips, e.g. a SDR/Rec709 clip, must be assigned to their right color space manually. I never heard they must be rendered firstly or so.

4, edit your timeline as usual and adjust brightness with FX-Levels and color with ColorCorrector(1st) if needed.

By rendering please try both the HDR and HLG output and see which one does fit your hardware.

Thanks.

vkmast wrote on 4/20/2021, 5:32 PM

User Yellandkeil seems to want you to read one of his posts, but unfortunately for some reason forgot to give you the link for it. (Please don't forget to thank him.)

Yelandkeil wrote on 4/20/2021, 5:37 PM

@vkmast, could teach me by chance how to make that link so that next time I do it myself. Thanks.

Teagan wrote on 4/20/2021, 5:38 PM

I have all of my clips correctly set to their correct color spaces in the project media section. The HDR ones being HLG rec 2020 1000 nits and the SDR ones being Rec 709.

I'm not sure how this explains the luminance value changes in how they changed.

My main editing screen is P3 hdr400 and my preview device is a 4k TV that has most of rec 2020.

The colors are fine on everything, it's just the luminance values that I am having a problem with.

vkmast wrote on 4/20/2021, 5:44 PM

@Yelandkeil highlight and copy the address. Paste it to your comment.

Click these buttons to learn more. (not on this comment, mind, but on the bar above the comment box.)

Yelandkeil wrote on 4/20/2021, 5:58 PM

So, your editing screen is P3-DCI, then you should set your project to

View Transform: P3D65 (ACES)

This is important! Without the correct simulation of preview you can't edit your timeline.

I think you haven't read my text, therefore still didn't understand what ACES is.

Pardon me.

Let's see at first, the rendered file from Vegaspro should have these parameters, pls compare with yours:

Teagan wrote on 4/20/2021, 6:03 PM

The rendered file has those settings exactly (except 23.976 fps and the bitrate), and looks great on my 4k TV but I was under the impression that the view transform has to be the same as my output color space? When I set it to p3d65 simulation or other ones like that or even rec 709 the luminance values go all above 1000 up to 3000-5000.

Basically I'm using the rec 2020 1000 nits view transform and using my scopes and eyeing it on my 4k TV to see if it looks good. I have them all calibrated. It does look incorrect on my editing screen but I just ignore that and use the calibrated TV.

Yelandkeil wrote on 4/20/2021, 6:08 PM

question 2, a 4k-TV that has rec2020 color depth doesn't mean it supports HDR.

or does it?

I have 2 HDR monitors with the same specification.

I don't know how to deal if the edit display doesn't match the 2nd preview in color spaces.

Teagan wrote on 4/20/2021, 6:10 PM

My 4k TV is HDR 1000 and has support for rec 2020 in deep color mode. When I play back the file on the TV itself (USB drive to the internal media player) I get the HDR trigger at the top right and it looks correct.

I'm not really sure how to get vegas pro on windows 10 to trigger hdr mode on my TV.

Yelandkeil wrote on 4/20/2021, 6:16 PM

Do you mean this one?

Teagan wrote on 4/20/2021, 6:19 PM

Yes that is enabled for the TV and my editing screen and the HDR symbol on the TV only appears on HDR sources like HDR10 from the file on the USB flash drive and built in apps or other HDMI in sources like blu ray players.

It does not activate for vegas pro on windows 10.

I'm not even sure if the brightness values are correct on the TV without the TV being in HDR mode.

I just use the scopes and render and it looks perfect.

Yelandkeil wrote on 4/20/2021, 6:23 PM

the vectorscope follows the preview window in vegaspro. Perhaps you could try:

1, open vegaspro on the TV-screen and you can use the Nit-indicator.

2, forget your TV and set your preview to P3D65 (and use the traditional waveform for brightness/luminance that confusing you permanently).

you still haven't shown me the file parameters you rendered.

Teagan wrote on 4/20/2021, 6:26 PM

Format                      : MPEG-4
Format profile              : Base Media / Version 2
Codec ID                    : mp42 (isom/mp42)
File size                   : 79.1 MiB
Duration                    : 46 s 755 ms
Overall bit rate            : 14.2 Mb/s
Encoded date                : UTC 2021-04-20 20:08:32
Tagged date                 : UTC 2021-04-20 20:08:32Video
ID                          : 2
Format                      : HEVC
Format/Info                 : High Efficiency Video Coding
Format profile              : Main 10@L5@Main
HDR format                  : SMPTE ST 2086, HDR10 compatible
Codec ID                    : hvc1
Codec ID/Info               : High Efficiency Video Coding
Duration                    : 46 s 755 ms
Bit rate                    : 14.0 Mb/s
Width                       : 3 840 pixels
Height                      : 2 160 pixels
Display aspect ratio        : 16:9
Frame rate mode             : Constant
Frame rate                  : 23.976 (24000/1001) FPS
Color space                 : YUV
Chroma subsampling          : 4:2:0
Bit depth                   : 10 bits
Bits/(Pixel*Frame)          : 0.070
Stream size                 : 78.0 MiB (99%)
Language                    : English
Encoded date                : UTC 2021-04-20 20:08:55
Tagged date                 : UTC 2021-04-20 20:08:55
Color range                 : Limited
Color primaries             : BT.2020
Transfer characteristics    : PQ
Matrix coefficients         : BT.2020 non-constant
Mastering display color pri : BT.2020
Mastering display luminance : min: 0.0001 cd/m2, max: 1000 cd/m2
Codec configuration box     : hvcCAudio
ID                          : 1
Format                      : AAC LC
Format/Info                 : Advanced Audio Codec Low Complexity
Codec ID                    : mp4a-40-2
Duration                    : 46 s 741 ms
Bit rate mode               : Constant
Bit rate                    : 192 kb/s
Channel(s)                  : 2 channels
Channel layout              : L R
Sampling rate               : 48.0 kHz
Frame rate                  : 46.875 FPS (1024 SPF)
Compression mode            : Lossy
Stream size                 : 1.05 MiB (1%)
Language                    : English
Encoded date                : UTC 2021-04-20 20:08:34
Tagged date                 : UTC 2021-04-20 20:08:34

This was a test, so I used a low bit rate. Looks great, the HDR has the punch and the SDR parts are not blown out.

What is the nits indicator in vegas? You mean the luminance waveform and histogram scopes?

Yelandkeil wrote on 4/20/2021, 6:36 PM

Yes that is enabled for the TV and my editing screen and the HDR symbol on the TV only appears on HDR sources like HDR10 from the file on the USB flash drive and built in apps or other HDMI in sources like blu ray players.

I have no idea. But it seems OK.

It does not activate for vegas pro on windows 10.

If vegaspro is active and set to HDR-mode, the TV must show a HDR-symbol, because the signal is already there. See:

I'm not even sure if the brightness values are correct on the TV without the TV being in HDR mode.

so to repeat:

1, open vegaspro on the TV-screen and you can use the Nit-indicator.

2, forget your TV and set your preview to P3D65 (and use the traditional waveform for brightness/luminance that confusing you permanently).

I just use the scopes and render and it looks perfect.

Sure, first your eyes, then the scopes.

Yelandkeil wrote on 4/20/2021, 6:41 PM

your output is perfect. And here the difference of scopes:

Teagan wrote on 4/20/2021, 6:55 PM

I never knew about the HDR output option and the HDR button, that's cool.

Thanks for the help, but this old Samsung tv just isn't popping up the HDR icon even with those settings enabled.

And yes, I'm using the HDR 10 bit scopes.

Yelandkeil wrote on 4/20/2021, 7:01 PM

doesn't matter if you're sure it just on receiving the HDR-signal.

so, case closed?

thank you.