Rendering background alpha channel media encoder

[suz davison]

Hi,

I can't find a way for Media Encoder to keep the composition background colour if I render it with an alpha channel (and RGB).

For example if I have a black object and I render it Quicktime-Png with the composition colour white, and render it directly in After Effects it keeps white as the background colour.

But if I do the same in Media Encoder the background reverts to black and the object can't be seen.

I don't want to put a white solid layer as then the background is not transparent.

Thanks

Suzie

[Mike_Abbott]

Am I correct in believing what you want is your object (black in colour) on a transparent background?

If so, I suspect you've got what you want in your Media Encoder render. It may look 'all back' in a media player as most media players wont show the transparency as a 'transparency grid' - they will show it as black.

Import your rendered file back into Ae or Premiere and put something underneath it to check.

[suz davison]

Hello Mike,

Thanks for taking the time to help me.

When I send the rendered file in AE, although it is transparent (with an alpha channel), the background is white. So the final (mov) rendered file has a white background.

When I render it in AME, transparent (with an alpha channel) the background is black. Which means the .mov file shows the background as black and a black object can't be seen.

I know it's a transparent file and can be used as one (I open the files afterwards and they're transparent, seen by the toggle transparency grid).

When they are uploaded to stock sites the background is black if I do it in AME (fine for white objects) but white in AE.

I can carry on in AE but it would be much quicker to do so using AME.

Thanks

Suzie

[Mike_Abbott · Accepted solution]

OK - I understand what you're after.

I think you'll find the difference is due to you outputting either a 'straight' or 'premultiplied' alpha. You have that choice in the Render Queue. I guess you've got 'premultiplied' selected in the RQ - hence the white 'background'. I don't believe you have that option in AME - the alpha will be 'straight' - giving you the black background.

So if you do want to output with a pre-multiplied alpha I believe you'll need to use the RQ.

One thing to note is that most editing software etc tends to expect a 'straight' alpha, so you might want to bear that in mind if you're uploading to a library. It might be worth having a word with them and seeing what they suggest, or at least checking their suggested upload / file specs. I can certainly see your issue.

[suz davison]

Hello Mike

Thanks for taking the time to help me,

It makes it all clear now!

Suzie

[Mike_Abbott]

Happy to help : )