How to export keyed green screen video using 4444 or 4444 XQ for alpha channel (i.e. transparent bkg) without creating massive 75 GB video files?

I think you may be being too impatient and the process is not as quick as you expect. The conversion from PR 4444 to HEVC is quite a lengthy process.

I exported a 63 second video called "TEST ALPHA" using PR 4444 to the desktop with a file size of 4.3GB

Next I right clicked and selected Services>Encode Selected Video Files

I then selected the following settings and clicked Continue . . .

Shortly after the following 2 files appeared on my desktop. The upper one contained Zero bytes. These 2 files are only temporary.

I had to wait almost 2 minutes and the above 2 files disappeared and were replaced by the one below which is HEVC, contains an Alpha Channel and is only 235MB in size.

So assuming your computer is around the same speed as mine, a 15 minute video would take about 30 minutes to complete.

OK, I feel your pain and frustration at being left in the dark, so just for you I will show you the simplest way of creating an HEVC file with transparency, whilst having a progress bar to gaze upon fondly.

Export your PR 4444 file from FCP and open it in QuickTime Player whereupon you select File>Export As>1080p (or whatever else you desire).

You will then be presented with this window where you select Smaller File Size (HEVC) and ensure Preserve Transparency is ticked. You can also change the destination and title if you wish.

Click Save and this window will appear showing a beautiful shade of blue progress line wending its way gracefully across the screen whilst simultaneously displaying an estimated finish time in elegant text.

What could be a more satisfying way of creating a tiny, high quality HEVC video with transparency?

That's all, folks!

The zero byte file appears while the process is being run. QuickTime doesn’t show transparency. Oddly QuickLook does. Select the 4444 in the Finder and press the spacebar. You should see ghosting of the desktop in the transparency areas.

HEVC. H.264. ProRess 4444 are all codecs that have different properties. In ProRes each frame is encoded separately at a high data rate to create very high quality recordings. The other two codecs encode in groups of frames with only a complete frame every 15 frames. HEVC OS a newer version of H264. It gets better quality at a lower data rate and can do transparency. Not all systems and devices can play it back however. It not as widely used as H264.

You do the conversion to HEVC in the Finder. Once the file has been exported with a proper alpha channel you can convert it in the Finder as I described. Once the file is converted and the alpha channel verified, you can trash the large 4444 file of you wish.

There is a much simpler way to achieve your goals without using alpha channels and saving tons of space.

Export your green screen video as a normal H.264 (extremely small file size) and use it with any future background of your choice and the FCP Keyer.

Export it like this . . . such a 15 minute video would be under 2GB

Right click on your exported ProRes 4444 file and select Encode Video file. Select HEVC and check on Preserve Transparency.

That’s the only way you can export transparency from FCP. (Make sure you haven’t rendered the project first in PR422.)

HEVC, H.265, is the only GOP compressed format that can do an alpha channel. You can’t do it directly from FCP.

Click the background task button or press Cmd-9.

For an excellent introduction to FCP start with Steve Martin’s 60 minute intro https://www.youtube.com/watch?v=HqUP7Zgeuck. For a more in depth introduction use the IzzyVideo tutorials. The version is a bit dated but the principles are the same. 

Ripple has excellent courses for FCP and other applications and many free videos on YouTube.

https://www.youtube.com/c/rippleguys

There's no need to open the Background Tasks window as Final Cut Pro like its professional sister iMovie has a progress pie chart to give you a visual indication of the exporting process.

Here you can see it is 25% completed.

Isn't technology great?

Dolmetscher wrote:

You are absolutely correct. I was being impatient. Well... in my defense... Apple does an absolutely dreadful job of telling its users what is happening... if anything.

All it would take is to add these two words... "In progress..."

But if you go back and do the same process that you just described, you will notice that there is ZERO indication from the software that anything is even happening.

Sorry, but you are wrong. Whenever you launch a Service (aka "Quick Action") that does not otherwise have any user interface, THERE IS a visual indication that it is working. In the menu bar, this thing appears (and it is rotating, too - I could have posted a gif, but now that you know it's there you can see for yourself).

That's a new one for me, Luis. Thanks.