Super Black/Super White Clip on Export

Hi everyone,

As far as I understand it, any blacks or white above or below 0-1024 are preserved in the export when using a codec like ProRes 4444/422. At least that's what I am experiencing, when I bring the render back into Resolve, there is data when I pull up the blacks.

For delivery qc requirements often dictate not to have blacks below 0 IRE past a certain threshold, of which we have failed a couple of times now. Is there a way to get Resolve to clip anything below 0 IRE so that it cannot be bought back? When I've used Broadcast safe it bumps up the blacks to bring the data back into range. I just want the blacks below 0 IRE removed.

Thanks!

James

Add a timeline grade and use the soft clip feature in custom curves with a high shoulder of 0.1. Won’t make any difference to the image but will clamp the signal. Alternatively make a lut that doesn’t do anything, Lut’s also clamp

You can not record 10-bit integer values lower than 0 and higher than 1023. What you're experiencing has to do with how those code values are interpreted on playback.

You could define that 0 represents black and 1023 represents white. But you could also define a more traditional interpretation where black is recorded as 64 and white is recorded as 940.

This of course results in values that are darker than black and brighter than white. They are generally invisible on a calibrated display (in most cases). But either way, they aren't meant to be seen by the end viewer. There are several reasons why these out-of-range level excursions are beneficial.

In your case, the Prores 4444 is generally expected to have black at 0 and white at 1023. Prores 422 flavors are generally expected to have values between 64-940 for black and white respectively.

Prores 4444 can not record superblack and superwhite while Prores 422 can. You can choose to disregard these guidelines and for example record black/white as 64 and 940 in Prores 4444, thus allowing it to convey superblack and superwhite, but the next person down the line interpreting the file may not know that and if they were to play back such file without taking into account your modified values it would appear lower in contrast on their display.

In fact something like that might have happened with your QC rejections in the past. If you recorded Prores 422 with data (0-1023) levels instead of legal (64-940) levels, what you consider to be black was assigned a lower value than where everyone else was expecting to see black. When read on the HD scope this value would fall lower than 0 mV. On a composite NTSC scope this value would fall lower than 0 IRE.

I am not quite agreeing with Igor.

Resolve is somewhat inconsistent.

For instance if you load a SMTE chart with a "pluge" and render it to various codecs in video levels in most cases the super blacks and whites are clipped, however not for H.264.

The most elegant solution would be to have a check mark in the Deliver page which would apply only for video levels output:

Include super white/blacks [ ]

Typically having super white and blacks as a deliverable is a mistake, however there are reasons, for instance for archiving purposes, to have those values maintained.

This clipping of pluge or any other superwhite and superblack values is a blessing and a curse.

While Resolve processes everything in floating point and allows superblack and superwhite in it's internal pipeline, at the time these values are converted to integers, i.e. when you write to a file, Resolve clamps to 0 and 1023.

This is good because it's hard to save illegal values, but it's bad because if you need to preserve superblack and superwhite, or even have a SMPTE compliant pluge, you have to bend over backwards.

Not all applications work this way. Media Composer for example is very transparent with it's use of superwhite and superblack. You can see it on the scope (which you can't on Resolve without some extra steps) and you can output it to file or tape. But for that same reason you have to use a legalizer in Media Composer if you have excess values.

Hi guys,

Thanks for your in-depth feedback, it was very useful indeed!

I did a test Igor where I exported a ProRes 4444 at data levels instead of video levels and bought it back in to Resolve. The data that was originally viewable below zero when increasing the lift had disappeared. This coincides with what you were saying, as with data levels there is no headroom for extra information,

However, I checked the DSM that is my source and this was exported originally at Data levels. How is it that a clip at data levels in Resolve has more information below zero IRE? Is there some sort of metadata in the DPX that tells Resolve that black is actually some other value than zero?

Thanks,

James

And Tom, I did try the soft clip and in the timeline it seemed to do the trick, but on export it hadn't done what I asked of it. When I pushed the soft clip really high, on export the black level was pushed higher but everything that was below it was scaled upward.

So basically the soft clip didn't seem to operate correctly on this particular DPX sequence