No alpha channel information in Adjustment clip MediaOut

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jacklib

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No alpha channel information in Adjustment clip MediaOut

PostFri Jan 29, 2021 4:59 pm

Hi,

I think that in the Adjustment Clip the alpha channel of the MediaOut is not transferred correctly, when MediaIn node is disconnected.

When I create a new Fusion composition, there are basically these 3 main options:

1) Open a Clip In Fusion Page
2) Add a new Fusion Composition
3) Add a new Adjustment clip

The signal flow for all three options obviously starts in the Fusion Page and then goes on to the Color page and then to the main output/timeline output, which is why we don't see any changes from the Color Page in the Fusion Page.

The only difference between option (1) and (2) is that in (1) a MediaIn is connected to the MediaOut by default and that this MediaIn always represents the selected clip. With (2), there is no MediaIn by default. If you remove the MediaIn for (1) or disconnect the connection to the MediaOut, then (1) and (2) - in my estimation - behave identically. I.e. a Fusion Composition is nothing other than a empty clip-template without MediaIn.

With an Adjustment clip (3), there is also a MediaIn, as with a normal clip, which is connected to the MediaOut by default. The MediaIn represents the current output of the timeline below the Adjustment Clip. You might expect that if you remove the MediaIn here, an Adjustment Clip should behave exactly like (1) and (2). But this is not the case.

I would like to illustrate what happens with a simple example. I take any clip. One track up I create a Fusion Composition. In this Fusion Clip I create a text node with a text and then connect this node to the output. In the Edit page, the text appears in the foreground above the first clip. Now I do exactly the same with an Adjustment Clip. I separate the MediaIn, create a text and connect it to the MediaOut. In the Fusion Page everything still looks identical. When I then switch to the Edit Page, the text now appears on a black background. The text background is not transparent and the clip underneath is completely covered by the text and the black background. In the colour page I see that a small preview of the MediaIn appears in the node, although it is not connected to the MediaOut at all?

If I now place the text on a black background in the Fusion Composition and in an Adjustments Clip and make the background transparent, i.e. set the alpha channel to 0 (Black-Background(Alpha = 0)->MergeBgInput, Text->MergeFgInput, Merge->MediaOut), then I see on the Edit Page that the alpha channel in the Adjustment Clip is obviously not transferred to the MediaOut, so the alpha channel appears black again. This behaviour is irritating and incomprehensible to me. Is this a desired behaviour or a bug?
iMac Pro 2017, 3,2 GHz 8 Core Xeon W, Radeon Pro Vega 56 8 GB, 32 GB RAM, Davinci Resolve Studio
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xunile

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Re: No alpha channel information in Adjustment clip MediaOut

PostFri Jan 29, 2021 6:42 pm

It might be a bug, but I would guess it has to do with the fact that an Adjustment clip also carries with it adjustments from the Color page. If you set the Composite Mode on the Edit page to "Foreground" it seems to use the Alpha.
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jacklib

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Re: No alpha channel information in Adjustment clip MediaOut

PostSat Jan 30, 2021 10:51 am

I don't know, if you try the other composite modes, you see that here alpha background behaves exactly like a black background? I think that can't be right...

There is something else. The Fusion-MediaIn in the Adjustment clip always shows the clips below it, but in the Colour Page you can also see the clips above it, but the changes in the Colour Page only affect the clips below.
iMac Pro 2017, 3,2 GHz 8 Core Xeon W, Radeon Pro Vega 56 8 GB, 32 GB RAM, Davinci Resolve Studio

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