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Level 1

18 points

Importing and Exporting Alpha Channel

Hi,

I have a Flash video (FLV) with an alpha channel (I don't have access to the original QT video). I used Adobe Media Encoder to convert it to Quicktime to import into FCP X to make a quick edit and export back out. How do I ensure that the video imports into FCP X with the alpha channel and exports back out with the alpha channel? I set Adobe Media Encoder to encode the alpha channel, but how can I tell if it imports into FCP with the alpha and exports back out with the alpha? Is there a way to check that in FCP? After I exported it out of FCP, converted it back to FLV and imported it into Flash, it no longer had the alpha channel. Not sure where I lost it along the way. When I exported out of FCP, I chose Apple ProRes 4444.

What things do I need to make sure I do in each of these converts, imports and exports and how can I tell if the alpha channel is there in FCP X?

Thanks,

Brian

Posted on Mar 27, 2012 2:09 PM

Best reply

dredcomm

Level 2

360 points

Posted on Mar 27, 2012 2:29 PM

The top right corner of the Viewer in FCPX has a dropdown menu where you can select what Channel to view. You can choose the Alpha Channel there. ProRes 4444 and Animation are both codecs you can use within the .mov format to retain an alpha channel.

View in context

32 replies

Mar 28, 2012 11:31 AM in response to Sullyville

Sullyville wrote:

> I just opened it in Photoshop as you suggested, and all I see is white - no foreground or background.

So now we know that Final Cut is not the problem.

Mar 28, 2012 12:04 PM in response to Sullyville

Sullyville wrote:

http://www.sullyville.com/intro.flv

This file is encoded with the On2 VP6A codec, which is the only legacy Flash encoder that supports alpha. I was able to load the .flv file into Flash and view it with transparency, but the greenscreen key is not that good. You would do better to get the original footage and do the chromakey again, this time with a garbage matte to block the man's shadow on the screen.

I was unable to retain the alpha information using QuickTime 7 or MPEG streamclip. Then I realized that Perian doesn't support VP6A.

In conclusion, if you're not able to obtain the original greenscreen footage, I would suggest you ask on an Adobe forum. Maybe someone there can explain how to export VP6A to a QuickTime format with alpha.

fox_m

Level 6

12,244 points

Mar 28, 2012 2:57 PM in response to Sullyville

I've got it converted to ProRes 4444 (403MB) -- I'm uploading it now... It will take another 90 minutes or so (if it doesn't fail). I'll post a link here when it's done. It's tested in FCPX...

[Turns out: Motion 4 handled your original FLV like a champ... not Motion 5, not FCPX, not even QT7Pro... However, I created an SD 720x480 4:3 project to import the video into and that's how it got exported. I think the "odd size" (276x433) made it incompatible with ProRes (the reason why QT7Pro failed to export to ProRes, but it did export to Animation+, but the alpha wasn't recognized in any other app.)]

fox_m

Level 6

12,244 points

Mar 28, 2012 4:23 PM in response to Sullyville

Ok -- it's available at http://sight-creations.com/fxexchange/intro.flv.prores4444.mov (right-click and Save Link As...)

I double checked QT7 by trying to add a "green screen" layer to the file, there was no alpha to work with...

Anyway, hope this helps. (let me know when you get this downloaded so I can remove it from my site - thanks.)

Sullyville Author

Level 1

18 points

Mar 28, 2012 6:00 PM in response to fox_m

That is awesome. Thanks so much for going to all that trouble. I have motion 5, QT7 and Adobe Media Encoder but never thought about the size of the video being an issue, so I never would have gotten there. I am downloading it now. I will let you know when it's down.

fox_m

Level 6

12,244 points

Mar 28, 2012 6:28 PM in response to Sullyville

It really was no trouble at all - I took a chance and it worked out (Motion 4 will handle quite a few more and different types of codecs than Motion 5 -- but I was still surprised when it handled the On2 VP6A format without issue!) It didn't take long for me to get there! If I had stayed with my original concept of using QT7, I would have gotten stuck, but I noticed right away the your .flv file was enabled for import, so I decided to try that one first... Glad I did because QT never would have worked.

Sullyville Author

Level 1

18 points

Mar 28, 2012 6:33 PM in response to Sullyville

I downloaded the file, fox_m. Thanks again. One thing though, I noticed that the video looks like it's in slow motion but the audio track is normal. I opened it in QT7 and it looks like the video is at 15 FPS instead of 29. I tried changing it to 29.97 but it didn't change it. After I imported it into FCP, I chose to double the video speed and it matched up great at the start, but then about half way through it's noticeably off. Doubling it doesn't quite work. Anything else I can do to make the audio and video tracks match back up?

fox_m

Level 6

12,244 points

Mar 28, 2012 8:50 PM in response to Sullyville

The original FLV file is 15fps. I saved it with the same frame rate so as not to create frame blending trying not to alter the original too much. I'm sorry! I didn't really think about issues in FCPX. However: in FCPX -- detach the audio. Select the clip. Go to the Retiming dropdown (clockwise arrow / speedometer icon) and select Conform Speed. It looks like it should sync up ok.

Mar 28, 2012 9:45 PM in response to fox_m

fox_m wrote:

Motion 4 handled your original FLV like a champ... not Motion 5, not FCPX, not even QT7Pro...

Interesting...cool how everybody worked together on this. Lesson learned: Don't trash your FCS installs!

Sullyville Author

Level 1

18 points

Mar 29, 2012 5:09 AM in response to Sullyville

Thanks a bunch. I tried the conform speed option, and it marks it at Fast 160%, but it isn't synched at all. It needs to be close to 200% but not quite there. When I put it at 200%, it is synched for about the first half of the video and gradually gets further off. I would imagine FCP is thinking 29.97 and the footage was at 15 fps, so double isn't quite right - I obviously don't know enough about this, but guessing. I don't see a way to choose any percentage you want. Ideas?

fox_m

Level 6

12,244 points

Mar 29, 2012 12:16 PM in response to Sullyville

I found out that the audio "stretched" further than I allowed for the motion project (so the last couple of seconds did not make it through - my bad!) so I'm reworking on resync'ing the audio with the video.

Sullyville Author

Level 1

18 points

Mar 29, 2012 1:01 PM in response to fox_m

Wow. Thanks so much. You really follow through. Very nice of you.

fox_m

Level 6

12,244 points

Mar 29, 2012 4:54 PM in response to Sullyville

Ok - it's uploaded: http://sight-creations.com/fxexchange/Fix-intro.mov (again, right click on the link and save as).

The beginning of the video takes a few frames before the subject walks into view. Since the original video is 275x433 mapped onto 720x480 (4:3) it kind of looks like he's walking in through a (black) doorway. You will need to crop the video in FCPX to match the original dimensions (or overlay something to make it look like he walks into view from behind something recognizable.)

Good luck with it -- it should all be there this time, and in sync.

Sullyville Author

Level 1

18 points

Mar 29, 2012 7:09 PM in response to fox_m

You are awesome. Thanks for the help. Sorry to be a pain, but I am getting a 404 error trying to link to the file and when I do a save as it downloads a file as HTML and then gives a 404.

fox_m

Level 6

12,244 points

Mar 29, 2012 8:04 PM in response to Sullyville

http://sight-creations.com/fxexchange/Fix_intro.mov ( I need to pay more attention when I'm typing! Missed the shift on the - for the underscore ...)

Importing and Exporting Alpha Channel