Why black level difference - HW vs SW export?

[Filmlinjen]

When exporting from a h264 timeline. It seems that hardware encoding makes the export darker than the software encoder. Why is this?

Watching in VLC makes the blacks crushed. But if exporting using software encoding the result looks like in premiere's preview window.

Looking at metadata the software encode says "limited range" i.e. 16-235 wheras the hardware encode does not. Making me think premiere's inherent color range in the preview might be 16-235. But this does not make sense in lumetri scopes which have 0-255 levels.

It just seems very inconsistent. Why is it and how to fix it?

Thanks 🙂

[R Neil Haugen]

H.264 is limited (video) range ... period. I'm not getting the issue you are, but then ... my settings in the Nvidia controls are that Rec.709 media is set to limited/16-235 so my system will handle all Rec.709 correctly in or out of Premiere.

I'm wondering about the metadata question ... maybe I'll have to test this. In MediaInfo, see if the hardware encoding also has the appropriate file information. Huh.

Neil

[Filmlinjen]

Thank you for the reply. I will further investigate.

Sorry for a late response.

I have not noticed any change by adjusting the setting in nvidia, I will try it again. All that did was making quicktime player cohere to the setting when playing back. VLC did not honor it at all.

Will do some more testing. Also we are on windows 10 win studio drivers, for the knowledge.

Thanks.

[Filmlinjen]

And yes, I checked in mediainfo. (Sorry I can not see anywhere to edit my post. If it is under "more" it is not showing for me, only a white blank popup" - no adblockers), 

[Filmlinjen]

Here are what mediainfo says:

The export settings are the same. Difference is HW vs SW encoding.

The software encoded file has some metadata that the hardware encoded does not.

[Filmlinjen]

GOP and reference frames are also different. But I have changed nothing in the settings. Although this has nothing to do with color.

[R Neil Haugen]

Which GPU do you have? I have an Nvidia card, and made sure to correctly set it so that video is treated as limited 16-235. Many people get it wrong, assuming they want 'full' 0-255. That isn't about how the monitor shows the image, but how it 'recognizes' the file.

Much standard video, all Rec.709, is not actually 'tagged' as 'limited', the cameras assume any player should 'understand' what Rec.709 media is. If the computer OS/GPU are set to 'full' 0-255, it can take normal Rec.709 media and crush the darks.

My colorist friends are always having to explain what 'full' and 'limited' really mean and how to properly set them. I had it wrong when I started out too.

This may be part of the problem.

Neil

[basil1891]

The software encoded file has some metadata that the hardware encoded does not. - this is it, imo