[Fatal bug?] Rec.709 attribute is missing after export

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Vit Reiter

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[Fatal bug?] Rec.709 attribute is missing after export

PostFri Aug 30, 2019 10:51 am

After export to ProRes HQ "transfer_characteristics BT.709" is missing.

Exports from DaVinci 16.1b1 were ok.
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Vit Reiter

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Re: [Fatal bug?] Rec.709 attribute is missing after export

PostTue Sep 03, 2019 11:35 am

I have found that if I set Managed Output Color Space to anything other than Rec.709 Gamma 2.4, the Transfer Characteristics attribute is included in the video export.

If I want Transfer Characteristics = Rec.709, I change Output Color Space to Rec.709 (Scene). See figure.
I still talking about ProRes, BT.709 video.


Maybe it will help someone before the Blackmagic bug fixes.
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Rohit Gupta

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Re: [Fatal bug?] Rec.709 attribute is missing after export

PostTue Sep 03, 2019 3:33 pm

This is an intentional change. We are tagging the files as 2.4 gamma to make the QuickTime Player show them correctly.
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Cary Knoop

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Re: [Fatal bug?] Rec.709 attribute is missing after export

PostTue Sep 03, 2019 3:57 pm

Rohit Gupta wrote:This is an intentional change. We are tagging the files as 2.4 gamma to make the QuickTime Player show them correctly.

Good move!
That will avoid a lot of "my video looks different when I export from Resolve" situations. :)
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Jean Claude

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Re: [Fatal bug?] Rec.709 attribute is missing after export

PostTue Sep 03, 2019 4:41 pm

Rohit Gupta wrote:This is an intentional change. We are tagging the files as 2.4 gamma to make the QuickTime Player show them correctly.


No more QT with Windows? Can you confirm if it is also applicable?
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Vit Reiter

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Re: [Fatal bug?] Rec.709 attribute is missing after export

PostWed Sep 04, 2019 12:06 pm

Rohit Gupta wrote:This is an intentional change. We are tagging the files as 2.4 gamma to make the QuickTime Player show them correctly.
I understand your effort, but the Transfer Characteristics attribute is necessary for further processing in television and film pipelines. The technicians are returning videos as damaged with the message that there is no Transfer Characteristics in Color Space!

Even the QC tool Interra Baton does not detect this attribute. Without the Transfer Characteristics attribute, you cannot use the video to make a package to the iTunes Store.

This is the wrong way. I did a test and QuickTime Player or macOS Quick Look still show a different picture result than DaVinci.
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Rohit Gupta

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Re: [Fatal bug?] Rec.709 attribute is missing after export

PostWed Sep 04, 2019 1:26 pm

Vit Reiter wrote:
Rohit Gupta wrote:...
This is the wrong way. I did a test and QuickTime Player or macOS Quick Look still show a different picture result than DaVinci.


Are you on 10.14.6 which is the minimum required? Older macOS has bugs due to which the color management will not work properly.

You should be able to render as 709 gamma I think as well and that should produce 709 transfer characteristics. Just don't choose 2.4 gamma.
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Vit Reiter

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Re: [Fatal bug?] Rec.709 attribute is missing after export

PostThu Sep 05, 2019 12:19 pm

Vit Reiter wrote:I did a test and QuickTime Player or macOS Quick Look still show a different picture result than DaVinci.
Rohit Gupta wrote:Are you on 10.14.6 which is the minimum required? Older macOS has bugs due to which the color management will not work properly.
Hmm, I did a test on macOS 10.14.6 and QuickTime Player still show a different picture result than DaVinci.

Can Somebody confirm that picture in QuickTime Player is the same in DaVinci?
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Joern Friedrichs

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Re: [Fatal bug?] Rec.709 attribute is missing after export

PostThu Nov 14, 2019 2:42 pm

Hi there, yes i can confirm. Looks like resolve 15 writes an quicktime atom "transfer characteristics" BT.709 to the rendered files. All files exported by resolve 16 are missing this atom. I guess this is why quicktime shows darker colour. The files reimported to resolve are looking ok and also imported to premiere for example. So the color data is correct. It is a viewing problem. And our whole company is going nuts because they cannot send the files to our customers.

And yes we are on the latest version of macos 10.14.

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Re: [Fatal bug?] Rec.709 attribute is missing after export

PostThu Nov 14, 2019 2:45 pm

Sorry, verything was said before. I should read before writing. :roll:
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Vit Reiter

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Re: [Fatal bug?] Rec.709 attribute is missing after export

PostMon Feb 03, 2020 10:40 am

Rohit Gupta wrote:You should be able to render as 709 gamma I think as well and that should produce 709 transfer characteristics. Just don't choose 2.4 gamma.
But how can we render the BT.709 with 2.4 gamma and to keep the attribute transfer characteristic?

Don't you just want to solve this problem normally? It is no longer possible to export videos with another gamma just because DaVinci cannot do it. It's nonsense to advocate it. It is not possible to solve the QuickTime Player capabilities by removing the required parameter. Stop the madness, please!
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Vit Reiter

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Re: [Fatal bug?] Rec.709 attribute is missing after export

PostWed Feb 05, 2020 6:01 pm

Source video:
Prores 422 HQ, 1920x1080p

DaVinci Output Color Space:
Rec.709 Gamma 2.2

After export from DaVinci is Transfer characteristics:
BT.470 System M


Why?
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Re: [Fatal bug?] Rec.709 attribute is missing after export

PostWed Feb 05, 2020 10:07 pm

Vit Reiter wrote:Source video:
Prores 422 HQ, 1920x1080p

DaVinci Output Color Space:
Rec.709 Gamma 2.2

After export from DaVinci is Transfer characteristics:
BT.470 System M


Why?

Was the source video BT.470?
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Vit Reiter

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Re: [Fatal bug?] Rec.709 attribute is missing after export

PostThu Feb 06, 2020 11:25 am

Cary Knoop wrote:
Vit Reiter wrote:Source video:
Prores 422 HQ, 1920x1080p

DaVinci Output Color Space:
Rec.709 Gamma 2.2

After export from DaVinci is Transfer characteristics:
BT.470 System M


Why?

Was the source video BT.470?
No, Rec.709 Gamma 2.4
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Re: [Fatal bug?] Rec.709 attribute is missing after export

PostWed Feb 19, 2020 2:48 pm

Hi,
We're having the same problem - client returned episodes with a failed QC from Vidchecker.
I would like to request a fix for this problem.
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Re: [Fatal bug?] Rec.709 attribute is missing after export

PostFri Feb 21, 2020 6:45 am

Vit are you still having issues? I'm getting correct Gamut: Rec.709 / Gamma: Rec.709 BT.1886 (1-1-1) tags exporting as Rec.709 (Scene) from Resolve 16.1.2 on macOS 10.15.3
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Re: [Fatal bug?] Rec.709 attribute is missing after export

PostFri Feb 21, 2020 3:01 pm

Christopher Dobey wrote:Vit are you still having issues? I'm getting correct Gamut: Rec.709 / Gamma: Rec.709 BT.1886 (1-1-1) tags exporting as Rec.709 (Scene) from Resolve 16.1.2 on macOS 10.15.3
Rec.709 (Scene) has gamma curve 1.96 (approximately). Try export Rec.709 gamma 2.4 then Transfer characteristic will be missed. Try export Rec.709 gamma 2.2 then Transfer characteristic will be BT.470 System M.

It just Rec.709 gamma 2.4 and 2.2 are important. I don't remember when it need export gamma 1.96?
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Re: [Fatal bug?] Rec.709 attribute is missing after export

PostFri Feb 21, 2020 6:50 pm

Resolve encoded files are correctly tagged and recognized in macOS as Gamma 2.2 and 2.4 by clicking info on the file showing (1-4-1) and (1-2-1) [undefined] respectively. Though I see what you mean by the missing attributes when exporting to Gamma 2.2/2.4 and cross checking with MediaInfo v19.09 as seen from the attached image.

For SDR content, macOS is looking for a standard (1-1-1) file i.e. (Color Primaries: BT.709 - Transfer Characteristics: BT.709 - Matrix Coefficients: BT.709).

As far as 'QT and macOS show a different picture than Resolve' - this topic is brought up on the regular and is currently being discussed here

To add to the confusion - Netflix on their specs page states 'For video mastering, gamma 2.4 was standardized in ITU-R BT.1886'.

SpectraCal on the other hand notes that there is a difference between BT.1886 and Gamma 2.4.

I haven't experienced a Rec.709 Gamma 2.4 (1-2-1) file out of a camera, it always comes in as Rec. 709 (1-1-1) but it sounds like your project calls for it.
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Last edited by Christopher Dobey on Sat Feb 22, 2020 11:43 pm, edited 1 time in total.
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Vit Reiter

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Re: [Fatal bug?] Rec.709 attribute is missing after export

PostFri Feb 21, 2020 9:23 pm

Christopher Dobey wrote:Resolve encoded files are correctly tagged and recognized in macOS as Gamma 2.2 and 2.4 by clicking info on the file showing (1-4-1) and (1-2-1) respectively. Though I see what you mean by the missing attributes when exporting to Gamma 2.2/2.4 and cross checking with MediaInfo v19.09 as seen from the attached image.

For SDR content, macOS is looking for a standard (1-1-1) file i.e. (Color Primaries: BT.709 - Transfer Characteristics: BT.709 - Matrix Coefficients: BT.709).

As far as 'QT and macOS show a different picture than Resolve' - this topic is brought up on the regular and is currently being discussed here

To add to the confusion - Netflix on their specs page states 'For video mastering, gamma 2.4 was standardized in ITU-R BT.1886'.

SpectraCal on the other hand notes that there is a difference between BT.1886 and Gamma 2.4.

I haven't experienced a Rec.709 Gamma 2.4 (1-2-1) file out of a camera, it always comes in as Rec. 709 BT.1886 (1-1-1) but it sounds like your project calls for it.
As you can see on your figure, all three exports are unusable.

Rec.709 Gamma 2.2 export has wrong transfer characteristic.
Rec.709 Gamma 2.4 export has no transfer characteristic.
Rec.709 Gamma (Scene) export has the right metadata, but I don't want deliver 1.96 Gamma video.

"QT and macOS show a different picture than Resolve" is an irrelevant argument. It is Apple decision on how their OS and apps work, but it can not be fixed so that DaVinci exports wrong metadata or omits one parameter. Who wants make grading inside DaVinci viewer without reference monitor is crazy but he can to do it with good Color management no matter how result shows QuickTime or other macOS applications.

Tell me this: How can I export Rec.709 Gamma 2.4 or 2.2 from DaVinci so that video has all three parameters and all three parameters will be right? Everything else is an odd discussion.
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Re: [Fatal bug?] Rec.709 attribute is missing after export

PostFri Feb 21, 2020 11:02 pm

Hey Vit could you please link to a downloadable clip with the correct tags you're looking for? (before imported to Resolve) From your experience when all goes well does Gamma 2.4 show up as 'Gamma 2.4' for its Transfer Characteristics or 'BT.709' in MediaInfo? Thank you.
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