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Hi.
My name is John Escobar, and in this video
we're going to discuss five tips for mixing and post-production
with ambisonic content.
In order to work with ambisonics in post-production,
we're going to need a DAW that is capable of multichannel tracks.
Currently, the two leading ones are Reaper and ProTools.
For first order ambisonics, you're going to need a track that
supports at least four channels.
And for higher order ambisonics, you're going
to need a track that supports at least nine channels.
You're going to need a format converter to get your A format
recording-- in other words, four discrete channels--
to convert into a B-format recording.
Depending on the microphone you're using,
there are a variety of plugins out there that will
allow you to do the A to B conversion.
Next, we're going to need a surround panner.
This shouldn't be your typical 5.1 or 7.1
panner, as that doesn't give you height, which
is one of the main characteristics of ambisonics.
This panner should enable you to do what's called head tracking.
One of the main reasons immersive audio works so well
is that it gives us the ability to replicate psychoacoustic cues similar
to the way we hear naturally.
If I have a sound source in front of me and turn my head to the left,
that sound now feels like it's to my right
because it's reaching my right ear louder and sooner than my left ear.
When working in VR, headtracked audio allows the viewer
to explore the environment with audio cues changing depending
on their position to them as they move, thus
giving a more realistic sense that you are
physically in the space you are seeing.
We're also going to need a playback converter--
or in other words, a way to monitor the mix that you're creating.
Remember, we're creating a 360-degree field around us.
Unless you're dealing with an Atmos theater
where you've got speakers all around you, the best way to monitor this
is going to be on headphones.
Therefore, your playback converter is going to take the mix that
you're creating in your DAW and output it to your headphones--
either in an ambisonic format using height, width, depth--
or pare it down to what's called binaural,
or emulating the way our ears work.
There are two different conventions of B-format ambisonic audio.
The difference between these two conventions is rather small.
It basically pares down to the order of your channel outputs.
In FuMa, you have a W X Y Z, where W is a negative 3 dB
gain versus the other channels.
And ambiX, where you have a W Y Z X, which
has all channels at equal gain output.
At this point, your documentation will also
come in handy because you're going to need
to tell your converter whether your microphone was front-facing,
upside down, or endfire.
We're also going to have the option to tilt our microphone so
that it more closely matches the angle of whatever camera it was placed to.
In other words, if your camera was offset this way,
you're going to be able to tilt your microphone so that it
matches the viewpoint of your camera.
And lastly, you're going to have some filter controls.
This might be just the generic ambisonic filters, which make the channels
interact with each other.
Or in some plugins, you also have rolloff filters
that you can apply to try and combat some ambience noises in the space
that you are in.
When setting up the workflow of your session,
you have a couple of decisions to make.
One easy way to approach this if you're only using ambisonics is to import
the already B-format converted audio--
which essentially means that decisions have already been made,
and you're just balancing that audio in relation to a visual.
Where it gets a little bit more complicated
might be when you're using an ambisonic bed of some sort,
and then individual mono or stereo sources in conjunction
with that to then pair to picture.
That could be a voiceover.
That could be other spots of instrumentation
or it could be sound effects that you're placing within the ambisonic bed.
If this is the case, the really important thing to keep in mind
is that contrary to other forms of mixing
where we might decide where things are placed and the general balance
and then add some effects, when dealing with ambisonic spacialization,
you're going the first want to add your effects and later do the spacializing.
In other words, you have to pre-render any effects on the tracks
or track that you're using and then decide where
that's going to go on a 360 space.
As you're working with your mix, you're probably also pairing this to picture.
Depending on what format you're going to end up using, whether it's
going to be some sort of headmounted device
or whether you're going to be doing web VR,
the workflow of how you sync audio to picture
is going to change a little bit.
Even though in traditional post-production
we typically think that working in headphones is not a great idea
and we like to have access to good studio monitors,
monitoring an ambisonic workflow can be a little bit
of a challenge in regular speakers.
Generally, most of us aren't in an environment that is full of speakers
on either side of us, in front of us, behind us, above us, and maybe
sometimes below us.
This would be the ideal setting, and we call that format Atmos.
Because most of us aren't going to have access to that,
headphones become the default way to monitor our mix.
However, one of the things that we lose when working in headphones
is a sense of height, mainly because the speakers are right against our ears.
The last thing you need to keep in mind when monitoring your workflow
is reference metering.
Once you've got a good idea of what your overall mix sounds like,
one thing that we're always concerned with is, is this too loud?
Is it not loud enough?
And how does it compare to other projects out there?
In traditional formats, we've got very well-defined standards
of dynamics or reference metering.
In immersive audio, these haven't quite been defined yet.
And it's also difficult to define them, because your reference changes
or your loudness levels change depending on the direction that you're facing.
The basic thing to keep in mind is that you
want to leave yourself plenty of room for dynamics, regardless
of what angle of the 360 environment you're looking at,
and that your final output is going to be loud enough but not clipping.
One final thing to keep in mind as you're setting up
the workflow of your session is going to be
what the final output delivery will be.
Whether it's going to be Facebook, YouTube, or in a video game,
you might have elements that are part of the project
but does not move around in the space that you're in.
We call that headlocked audio.
In other words, a voiceover might end up as a mono file that
is always in the center, even though the rest of the elements around you
will change as your viewer moves around the environment.
That means that your final output delivery might include various stems.
You might have stems that are headlocked stems, mono or stereo.
And in addition to that, you'll have first order ambisonics, second order
ambisonics, or binaural outputs.
Whatever your final delivery stems are, you're
going to compress that together into your final video format.
Starting with a clear idea of what your final delivery will be
is pretty important when setting up the overall workflow,
but keeping these five tips in mind will help you set up
an effective workflow for your project.
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