export with transparency

[Ludde]

Hi
I would like to know if I can export a chroma key sequence, that is if I have a blue screen shoot, and then have the blue as transparency when you export sequence, ?

[GrassValley_KH]

You can't export an alpha channel out of EDIUS, but you can export a second file which simply has a two-colour Key for compositing in another application.

Within the Chroma Key control panel, you should see an option called "Show Key". Use this to create a mask.

[Ludde]

Hi
I don´t have any option " Show Key " but I have something called Key display, is that the same ? anyway, so how is the workflow, I check the key display and then export movie as 32 bit targa seq ?`or am I missing something here ?

[Claire]

Hi
I don´t have any option " Show Key " but I have something called Key display, is that the same ? anyway, so how is the workflow, I check the key display and then export movie as 32 bit targa seq ?`or am I missing something here ?

If this works how I think it does, since it's only Black and White there is no need for more than 24 bit codec on export. It could be HQ AVI.

In After Effects, use the B&W AVI as a luma track matte for the original tga sequence so the matte is on the top layer. This will produce your 32 bit video which can be saved from AE in various 32 codecs. Alternatively you could combine the two in Edius bin by making an alpha matte with them.

[Ludde]

I don´t have AE, however, seems interesting, your suggestion to combine them in the bin, but how do I do that ?

[Claire]

I don´t have AE, however, seems interesting, your suggestion to combine them in the bin, but how do I do that ?

Okay, well what you do is to first export your chroma keyed sequence, no need for TGA frames, a 24 bit AVI will do. This should appear in the bin.

Now select the "Key display" in the chroma key window, the image should change to a B&W image, this is your mask. Export this as an AVI and now you have two rendered files in your bin.

Select both of them (control/click) then from the right click menu choose "Convert" > "Alpha matte".

In this dialogue, for Fill Key select the mask as the key. For "Convert format" select Luminance matte.

Render in HQ codec as it can hold the alpha channel.

The resultant 32 bit video file now has transparency where the blue background was. This is the alpha channel, you can overlay other video with this in the same or another sequence or another project.

[Ludde]

Thanks !! works great :)