You don't have to anything. An alpha channel means it has transparency. It's about as no-brainer simple as it gets -- you just use it.
If you want to see the checkerboard you need to enable the transparency background in the composition panel.
The easiest way to tell if the video has an alpha channel is by selecting the video in the project panel and then look at the info displayed at the top just to the right of the thumbnail.
If you purchased that trombone clip it should have transparency. You can check it in a composition by dropping another layer below it.
You can also check the footage panel or the composition window and just view only the alpha channel. It should be black-and-white.
These are real basic AE skills that you should have. If you are confused about the user interface or how to use the various panels please check the help files.
Thank you for your reply Rick.
A selling point for the animation was that it has an alpha channel, however when I drop it into the comp over the rest of my animation it still has a background and covers all other imagery. When you say "enable the transparency background", how do I do that?
This piece of footage may not have an alpha channel. You can check it -- highlight it in the project pane and go File>Interpret>main. In its alpha channel setting, let AE guess -- it's REALLY good at guessing this.
Then place the footage in the comp. if you still can't see the layers below it, you do not have an alpha channel and you'll have additional work to get rid of the background. What kind of work? No clue -- we can't see what you're working with.
I want you to take a screenshot of your entire AE project. Make sure that the footage you're having problems with his selected in the project panel. Select the footage in the timeline and press the u key twice to reveal any modified properties to that layer.
If you do not see RGB and Alpha next to the thumbnail of the footage in the project panel select file> Interpret footage>Main to bring up the file interpolation panel and see if there is an option to enable the aloha channel. If there is not your footage does not contain an alpha channel. Check with the folks that supplied the footage. Sometimes they send you two copies of the footage, one of them is black-and-white and you use that for a track matte.
When you checked all the options and taken a screenshot of your whole app then just drag it into the reply field on this forum so we can see what's going on.
By the way the enable transparency grid switch is at the bottom of the composition panel, it's a little icon that looks like a checkerboard, you should have a tooltip the pops up when you hover over it, and it's fully described in the help file along with screenshots.
That movie does have an alpha channel but it is also filled with blue pixels that make the sky. Therefore there is no transparency.
You can check the movie by loading the movie in a new comp or by just opening the footage panel by double clicking. Right at the bottom of the Composition Panel, sixth from the left is a little red, green, and blue icon. Click that and choose alpha only (something like that) and you'll see there are no white pixels. White is transparent...
The transparency grid will also show you any transparency in the footage. That switch is just to the left of the Active Camera switch in the Comp Panel.
I don't know what the description of that clip is on the site where you got it, but unless they have a version with only the sun or only the sun and the clouds you don't have transparency. There is not enough unique color in the movie to key anything out and I don't know what happens when it plays but I don't think it's going to work for you.
You might want to check out the AE help files on transparency: Use alpha channels, masks, and mattes in After Effects
One more thing, the movie is 24 fps which is not a standard frame rate for video. If you are mixing live video from any camera you should verify the proper frame rate and make your purchased assets match the frame rate. If you are doing animated graphics then you are asking for a lot of problems working at 24 fps that will happen if you are not very careful with the speed of the motion in your frame. I do not know what all the fascination is with 24 fps. Movie projectors have butterfly shutters in them that give you 48 flashes of light each second when the film is played back at 24 so you don't get a headache. The lower the actual frame rate the higher the possibility is that you will get stroboscopic motion artifacts on things that move in the frame because that's just the way things work. I wrote an article on that that is in the FAQ. If you really want to do video at 24 fps you have to be aware of all those problems, avoid critical speeds, and be prepared to have the frame rate react badly with the scan rate of computer displays. These effects can kind of be mitigated by interlacing your 24 fps (23.976 really) video and adding 3:2 pull down so that it plays back at 29.97 (video standard for most of the world).
Sorry for the rant... Just things that anyone doing video should be aware of so their hard work is not spoiled.
Okay thank you gentleman! I ditched that animation and will contact the company who sold it. Otherwise the project turned out great
Rick, I appreciate your advice on the frame rate. I was actually producing the commercials in 23.976, I think it accidentally switched when I clicked on the preferences tab before taking the screen shot. I am surprised to hear that you don't recommend 24fps (what many videographers refer to 23.976 as), as it seems to be the modern industry standard. I'm not familiar with what a 3:2 pull down is, but my understanding of the fascination with 24fps is that it looks closest to film, giving it a romantic, nostalgic feel. As a professional videographer of 5+ years (I'm new to animation), I find it jarring when someone uses 30fps (29.97)- am I just seeing this wrong? It seems like most up and coming videographers are using 24fps or 60fps on a 24fps timeline. No?
Here's the deal. Any cinematographer that's ever worked with filmic with him at those about critical panning speeds when shooting 24 frames per second. You have to be extremely careful or just a simple plan will turn into an unwatchable shot. The American cinematographers handbook has several fedicated to clinical panning speeds. You search any of the cinematography or videography forums that are frequented by amateurs or people that have never worked in film you will find all kinds of questions about how come my shots look horrible in the action is not smooth.
Feature films since the advent of sound have been shot at 24 frames per second and the projectors run 24 frames per second but the butterfly shutter gives you the same effect as seeing duplicate frames Sean at 48 frames a second. Is the same effect that interlacing gives to television.
Another fact. In broadcast television there is no such thing as non-interlaced playback at 29.97 frames per second. If you originate at 24P your crew frame rate is 23.976 and broadcasters and cable companies use hardware to encode that signal at 29.97 frames per second interlaced (approximately 60 fields Per second) and you end up with a combination of identical fields for two frames and then one frame that has one field from one point in time and another field from another point in time which has the effect of slightly blurring that frame. They call this 3:2 pull down. It's the only way to get 24 frames per second video into a format that can be broadcast universally.
All television sets run interlaced. If you send progressive footage on the broadcast channel then you just have identical slices of time on the pairs of fields that make up a frame. It's exactly the same affect as the butterfly shutter they put in motion picture projectors so that you're a highball and your brain is shown 48 individual images per second and those images are in pairs of identical images.
Only on computer monitors or on television sets that are receiving signals from a device like a Blu-ray player or a cable box with the capability of broadcasting 24 frames per second video do you actually get 24 frames per second with individual frames. 99% of your audience, if you are making commercials for television are watching at interlaced signal.
When we first started to be able to do 24P video everybody got excited that 20 4P would make video look like film
Thank you for the breakdown, I have a better understanding through your knowledge. However, I think there must be a widespread misunderstanding about this as many, almost all, jobs I am hired for request 1080/24p as the deliverable format. I rarely do broadcast/cable videos anymore as many local stations use station crews to produce commercials, and almost everything I do produce, as well as almost every one of my peers, is solely shared online. I would be floored if I client asked me to turn in work at 29.97.
That's because most of them are young and never worked in film and don't understand how television works.
There is such a huge misconception that 24P video looks like film and it doesn't. And very few people understand that everything that is broadcast over the air goes out at 29.97 frames per second interlaced. Cable, when you pay extra for the premium box and the premium service is the only way to get a different frame rate.
By the way some broadcasters send out HD 720 P. Everything else is set out at 1080i and it's because of the bandwidth requirements for and interlaced signal are half that of progressive.
If you want more flexibility in your motion design use the higher frame rate. Otherwise you have to be very very careful about judder.