Hey everyone, one of the questions I get
from time to time is what's the difference between an upstream key and a
downstream key, and then another question I get is, Wwhat is an upstream key and
what is it downstream key? Likewise, what is a key? Let's start by answering that
one. So, hey, everyone my name is Doug, I run a video production company in Orem, Utah called DJP, and we do live events of all sorts. And I've had this YouTube
channel now where I've been talking about video production-related topics
for about three and a half years. And I have people ask me questions all the
time about how to get started, and about some of the basic concept, and asking for some explanations, so do my best to try and
explain this. This is a very-much unplanned video -- I just happen to be in
the trailer and I thought I'd put this together. So first of all, what is a key?
So a key is basically any graphic or any video source that you overlay on top of
one another. So the most common example you probably seen, that would be a lower
third where you see someone's name placed at the bottom of the screen using
a computer graphic. You might also be familiar with the term 'green screen,'
where that's actually a key where they're removing the background by
removing anything that in the video that happens to be green. That's done with a
key so the Blackmagic ATEM switcher that I'm gonna be using and demonstrating on
here -- It's to do those as most other switchers are. The terminology here
may differ from your own switcher but conceptually these things are fairly
standard, so the video production industry has kind of
standardized on this portion of the workflow, so even though the names might
be a little bit different and you might go about setting these things up a little
bit different one manufacturer to the next, conceptually this is going to apply
to pretty much every switcher that's out there. So, okay, we've got key defined.
What is the difference between upstream key and a downstream key? Well, before I
can really define that we need to talk about transitions. So if you look at my
screen here, I'm going to do a transition between two different shots.
So I've got a shot of me and the shot of my computer and I'm doing a dissolve
one to the other. In order to do that you've got your preview and you got your
program. A transition switches between those. And at a simple level that's
that's the fundamental of what's happening there.
However, there's actually more going on there than than, that so if we take a
look at the software here, (this is the ATEM Software Control for controlling
switcher) this section of the software right here is used to set up your next
transition, and normally we just have Background turned on, and what that
really means is when I'm going to do a transition from one shot to another. It's
going to transition from whatever's currently live -- whatever is currently on
program, to whatever is on the Preview bus, so think of this Background button
being the Preview bus. It could actually even write Preview on there, because
that's exactly what's happening. So whatever is selected in this box is what
we're going to be transitioning to when we hit our transition button. Next to that
we have buttons for key one and key two now these are upstream keys, and what do
we mean by Upstream? Upstream essentially means that these are keys that are
included as part of the transition, so in the transition from whatever's
on Preview to Program, anything that's on an Upstream key is going to be
transitioned with it. The downstream key happens after that, so whatever you place
on a Downstream key is going to stay on screen no matter what you're doing with
your transitions. I very often use downstream keys for things like logos --
company logos, so I place a bug in the lower right corner of the screen that
just stays up the other for the entire program. It doesn't go on and off with
changes in shots. So that's really the difference between Upstream
Key and Downstream Key at a fundamental level. As far as implementation from one
switcher to another, it varies. Like, for example, this Blackmagic switcher
that I'm using, the Downstream Key has a lot fewer capabilities than the Upstream
Key does. The Downstream Key won't do what we call chroma keying, which is
where you have a green screen, where you're taking out the
green to place an object in front of it in front of a background. That can be
done with an upstream key, but it can't be done with the downstream key.
Okay, so let's actually take a little more of a look at this, so if you look
at my Preview window in the upper left corner of the screen there, when I press
this Key One button it's going to show this sample graphic that I've
put, and it's showing it on top of what's on the Preview, so the background and the
Preview has Key One added on top of it, and if I press Key Two you're going to see
that Key Two is added on top of that, and if I do a transition those will all be
included as part of that transition. The transition back. Now, the other thing you
can do here is, you don't have to include that background as part of your
transition, so we'll turn off the Background button, and that means that
the Preview is not included of part of the transition, so if I do that
transition, you'll see that it's just adding the graphic on top of what was
already there. Now, likewise, if we hit the Background
button now -- here the transition and it does actually include the background in
that transition. So with that we can create layers, and we can do some pretty
cool things. In a minute I'm going to dig into a little more about the input specific
implementation that Blackmagic has here with the keys, but that's kind of the
fundamental idea. So we've got a section here of whatever is going to
be included in the next transition. Above that we actually have some buttons to
take those on and off of air without having to do a transition. So if I press
this one, it's going to take Key One and put that on air without having to do a
transition. Likewise Key Two and take those back off again. Now one thing
that's a little strange here (I'll put these back on screen) you'll notice that
these two are lit and the Key One and Key Two are lit but they're not included in
that preview window. That's just a little quirk about the way this particular
switcher is implemented. So, effectively, instead of meaning this is
what's going to be on screen after the transition, it means we're going to
change the state of that as part of the transition. So if I turn those off (you
always have to have at least one selected by the way) so
In order to turn those off you have to have Background selected. So you notice
here that even though Key 1 and Key 2 are not lit, they're actually included in
that preview window. And if I do the transition, they will stay on screen. So
effectively what we have here is pressing these two buttons toggles
whether that layer is included as part of the transition. Now, that's kind of a
Blackmagic thing -- you won't necessarily find that other switcher manufacturers do that
that way. So it's a little counter-intuitive if you ask me, but
that's but that's how it works. So I'll do the transition again. There we
go. You can see that we have our background, key 1 and key 2 all on
screen. Now, I'm going to actually do a downstream key here. I need to change the
graphic, so bear with me. Okay, so I've got -- I what I've done is I've placed a lower
third in Media Player 2, and then you see that I have selected -- Let's see, there's a
upstream key, there, okay, there we go Downstream Key, so fill source this is
media player 2. You also have to use media player 2 for the key. By the way, fill source -- that's the foreground, and the Key is basically the
transparency information. So you can have graphics that are partially transparent.
In this case I'm using a file that doesn't have any transparency in it, so
I'm using what we call a Luma key. I can get to more than or that in a minute.
I'm using a Luma key, so everything that's black actually becomes transparent
in the image. The workflow here is left to right, so you've got your your Preview
and Program, you've got your transition (the t-bar is part of the transition) and
then you've got your Downstream Key here. So that's kind of a left-to-right flow
of what's actually going on inside the switcher. Now, this section right here is
for those downstream keys. Downstream key 2 is actually the lower third that I set
up here, so if I press-- In this case, I'm gonna press the auto button, you'll see that
adds the lower third on top of that graphic. Now -- actually, let me change the
video source on that. There we go. So you'll see you're seeing my graphic
with the Downstream Key on top of it, and likewise, if we do a transition from
Preview -- so we've got our Preview background graphic, we've got Key One
selected, and if I do a transition you'll see that the Background video, that key
have transitioned on screen, but the Downstream Key stays on top of both of
those. Ok, and I'll transition back. The Downstream Key still stays on-screen. Now, another thing you can actually do here is, you can actually have the switcher
remove the Downstream Key when you do a transition. That's done with the Tie
button here, so if I click on Tie for Downstream Key 2, and then I do a
transition, you'll see the Downstream Key has actually faded off a screen, so even
though the Downstream Key is not technically part of the transition, you
can actually have it be brought on or off screen while you're doing a
transition. That's just a convenience feature -- the downstream key is not part
of the transition, I'd need to need to make that clear. A couple other buttons
here that are that -- you got an On Air button here. (I'll turn that Tie off) So I've
got the On-Air button here. That just turns it on and off without a
transition. And then the Auto button slowly fades it on and off, and the
duration of that fade can actually be set here in the downstream key
properties. All right, with upstream and downstream keys defined -- and hopefully
you've got a better idea of what that's all about, let's talk about some of the
different capabilities that they have, because on this particular switcher and
many others that they can do different things. So, the downstream key on this
particular switcher only has the capability of doing either alpha keys or
Luma keys. So alpha key is where the image that
you're keying actually has its own transparency information, included as
part of the file or included as part of the video. A Luma key is where it
determines transparency based on on the brightness, so white would become fully
opaque, and black is transparent, and you can adjust those levels, so at what point
in that range between black and white actually becomes transition as well as
the width -- whether it's a hard stop between
one level of one level of gray and another, or whether it's more gradual.
So you can actually create some transparent transparent effects, sort of
like I did with this graphic right here. So you can see it's partially
transparent even though this is just a Luma Key.
The Downstream Keys actually have the capability of doing Luma keys and Alpha keys. They cannot do (on this switcher) cannot do a Chroma key, for
example, so you can't use -- you can't have a green screen used for a downstream
key. You wouldn't normally do that. Most of the time when you're doing a Chroma
key it would be something you'd want to bring on an off as part of a transition.
That's why, on the Blackmagic switcher, the Chroma key is only available in the
upstream key. Let's take a look at some of the other differences that are here
as well so if we look at the settings for the upstream key. So we have Luma,
which is again is based on intensity. That's also where you find your Alpha
key as well. You have chroma, which is based on color, so we can set for example a
green, we have Pattern, we have DVE (Digital Video Effects) Now the DVE is
basically referring to the ability to resize, rotate, and move a video source
around. This will be useful for something like a Picture-in-picture and I actually
use that fairly extensively on a lot of the productions and I'm doing. This
picture in picture that I'm doing right here I'm actually doing with a total
separate feature is called a Super Source which is specific to the
Blackmagic higher end switchers, so using just an upstream key you wouldn't be
able to recreate what I what I'm doing here in this video. Let's take a little
bit harder look at the Luma key so look at my Preview window you can see that
I've got some some blue bars. The reason that that's actually showing in the way
that it does is because the graphic that I'm using actually does have
a separate transparency layer to it and if you look at my settings here and
Player One is the actual graphic and then the Player One Key is that
transparency information from that file. If I was using a file that did not have
its own transparency information, then I would want to use Player One and you can
see here that the darker portions of the image
are transparent and the brighter portions are actually visible now. If I come down
to the Clip and Gain settings, here we can adjust the level of transparency, so
as I adjust that you can see more is becoming visible, and then the gain
basically controls the transition between them. So you can see partial transparency versus just a simple "is it visible or is it not." So you
can you control that with the gain. The combination the two of -- those two
controls actually interact with one another and so, you might want to tweak
them a little bit in order to get a perfect key for what you're trying to do.
I'm gonna put it back on basically an Alpha Key. So I'll put these settings
back to their previous -- there we go. Okay, so, we've got these blue bars that are
that have transparent information and it's allowing the background to show
through. Okay, let's talk about flying keys for a minute because the flying keys
allow you to do some simple animations as part of your transitions. So the
flying key here -- the settings are here as part of the -- and we're
still on the Luma key, so scroll down to Flying Key, and it's an option you can
turn on and off. And then it's got some properties here to set its position so
in the case of the Blackmagic switchers they use a coordinate system that's
based on 16x9, so if I move to position X: 16, the graphic moves over
half a screen, because now the center position is on the right edge of the
screen. So we want to go all the way off screen, we'd actually do 32, before I do
that there will actually want to demonstrate something else so bring it
back on screen to 0, 0 center which is the center of the screen. There are also
some size options here, so we can say 0.5 which is half size. Go back to
full size, 1.0. There's also a rotation parameter here so if I rotate 180
degrees you can see that that's rotated. So what I'm gonna do here -- I'm actually
gonna take -- I'm gonna move it off to the right of the screen I'll go half way
to start with and then I'll go all the way which is X position of 32. My
position is X 32, Y 0, Size is 1, so full size and rotation is
180 degrees, so effectively it has been moved off screen and flipped 180 degrees.
And then what I'm gonna do I'm gonna set key frame "A" so I'll click the Set A
button. All right now, let's reset all this, bring it back on screen, set the
rotation back to zero. The other thing I'm going to do is I'm going to take it
and I'm going to move it down past the bottom of the screen for preset B, so to
move down that's actually a negative number, so if I move -9 that's
half way off screen. If we're going all the way off screen, do -18.
So now that graphic is fully off screen below, and I'm going to click Set B. So
now what we've got is I've got two presets -- one where the graphic is off to
the screen to the right (well, your right) And then we've got one where the graphic is down below. Now if I want to animate that
I click one of these Run To buttons. So we've clicked the Run to A and
you'll see it went from below to off-screen to the right. This will make a
little more sense if I click on the Full button. You'll see it rotate back into
position and come on screen all at the same time.
If I click on B it'll move down below the screen again, so Full brings it
back on screen and centered at 100% size and then we've got our other presets. It
also has some other presets built in here as well, so if I click on one of
these other buttons under the Run to Infinite section, like for example, this
one takes it off into the upper, left-hand corner. In order to restore it you have
to click the Full button again to bring it back. But there's some others here as
well. Like to shrink it down in the middle of the screen, go off to the right
edge. Yeah, so several different options here as well. Now the downside to this is
these don't automatically (at least with this switcher) don't automatically happen
as part of the transition so I can do the transition and the graphic goes live,
but it doesn't automatically animate so you're gonna want to have that set up
before you do the transitions. For example, I'm going to move the graphic
down below the bottom of the screen do the transition you don't see any
change there but then I'll press the Full button, and there you go, so the
graphic animates on-screen. Now in this particular case, the background didn't
change as part of the transition because my background and my source are the same, so let's actually do this again using the computer graphic behind. There we go.
So transition, got the computer graphic -- my computer image behind the
upstream key, upstream key 1 on top of that, and I'll do an animation
here, so I'll click B. There you go. So normally you have that off screen. If
you want if you just want to have the transition without changing the
background, what do we do? We go back here to the Background button and turn that off,
right? So let's go back, let's bring the graphic back on screen, so you can
see it's still active, then I'll I'll move it down below the screen, and
then I'm going to turn the Background off. Perform the transition -- you don't see
any change at that point, you can then press the Full button then bring it on
screen. So there we go we've done a transition with a graphic using features
of the software. In most situations you're probably gonna want to automate
this a little bit using the macros feature, and I could do an entire
separate video on the macros feature in switchers. Basically that allows you to
do with little sequences of commands like this, in an automated fashion. So
take the time to get to understand the macro feature in your switcher, it
actually allow you to do a lot of cool things you probably wouldn't be able to
do otherwise. It makes a lot of things easier
things like sequences of things that you do frequently you just put inside
of a macro, and and then a single button press will actually perform that series
of actions for you. All right, now let's actually, let's get back, so full screen,
transition the background, do the animation. There we go. Okay, so we've got
the flying key there, we've done a Chroma Key. Let's actually move over to
DVE, so in this case a DVE, as I mentioned earlier, is going to be taking
a separate video source and moving it around or shrinking it down. So I'm gonna
choose -- let's see, let me turn off my existing key here. There we go. Alright so... Choose my video source. I'm going to use -- let me switch things up a bit here so no
computer background, and then I'll put me live, there we go.
And then I'm going to choose my camera as the source for the DVE, and then I'm
gonna say USK1 Next, so that actually appears on screen. Now, I'm picking up the
whole screen right now because I haven't resized or anything, but if I come down
here and I change the size to, say, 0.4... There we go, I shrank down, and then I can
change the position, so let's move over to, say, position 10... that's a little too
far, I'll go and maybe 8, there we go, for the X, and then let's say 4 for the Y. So there we go, there we have a picture in picture that will happen as part of
transition. So I'll do the transition. Bingo! So there's my video on top of the
computer graphic, transition back... the picture in picture comes on and off
screen with with the transition because it is being it's being done with the Upstream key. Some other things you do here as well, you can actually add a
border, so let's do bevel in and out there, and then give a little bit of a
width here, so you can actually see it. There we go, so a very slight border on
there -- little inner -- there you go. A little thicker you can see that on screen --
transition that on and off. Now what do we want to do if we want
picture in picture to transfer on without the background? We, again, turn
the background off, perform the transition -- the picture in picture comes
up on screen without changing the background behind it. And again if we do
the same thing again, same thing happens. Now, turn the background on again -- now if
I do the transition, that layer behind, the preview video source, gets
included as part of that. Okay, all right so I think that kind of covers at least the
high-level concepts associated with the Upstream and Downstream key that we have available on our switchers. There's a ton of things you can do by using a combination of different settings that are in there. So, for example I've read on
a forum recently somebody who's looking for a way to do a black and white image,
and you can actually do that with a keyer on these on these switchers. So there's lots of little tricks that you can do on here. And some of the more recent switchers have even better capabilities. So the
more recent ATEM switchers, for example, have much better chroma keyers in them than this model that I have and some of the older ones. So if you're looking
to do a green screen some of those newer models do a better job of that. That
includes the new ATEM Mini that ships next month. It actually does a better job
of chroma keying than this $4000 switcher that I've got here. so...
Anyway if you guys have questions about this, please don't hesitate to ask but
do please try and keep them brief. I do have a lot going on I don't have a ton
of time to research answers, but I am happy to answer questions that I can off
the top of my head. So if you're new to the channel please consider subscribing.
I do video production-related content about once a week. This is actually the
second video this week. I've been a little bit slow recently, but I've got
more coming and I try to address topics that people request, so if you have
something you want to learn about please don't hesitate to ask. Leave me
a comment in the description -- leave a comment down below and I'll put them on
my to-do list, and hopefully address topics that are actually
meaningful for people that are here viewing the channel. So, anyway, thanks guys for watching, and have a fantastic day!
