The Future of Film Mixing & The Need for VCA Folders

[Gregor B.]

What is the biggest difference between film mixing before and after the emergence of 3D audio? It’s summing vs. separation. Keeping signals separate, e.g. in the shape of objects is what makes Atmos truly remarkable and I believe the future will rely even further on separation.
Which is why future mixing concepts in film will not revolve around summing points, such aus AUX and routing folder but on something that group-controls signals at the source: VCA folders.
They look and feel like routing folders, but function like VCAs, except not just for the volume parameter but for all parameters, keeping signals separate so they can be routed anywhere.

In order to explain why this is crucial for film work, here are two simplified signal flow charts:



The green layer represents audio tracks in various formats (mono, stereo, 5.0…) of which there are easily between 200 - 1000 depending on the size of the show. The blue layer represents predubs (or subgroups) of which there could be between 20 and 50, and they are what you would often see on an S6 surface today, a very easy way to handle and control large projects. In practical terms, predubs have often been set up as VCA faders, allowing to control the volume of larger groups of sounds, while being able to spill and reach all underlying audio tracks. Later, the emergence of routing folders added possibilities to actually process each group with inserts and also send to reverbs (or other). The reason this worked for classic mixing (7.1/5.1/…) is because the signals were actually being summed and the new signal then processed.

Enter 3D audio / Atmos:



The challenge of 3D audio is its open architecture: Signals are often not being summed, but kept separate on principle. But you still want to treat them as groups. Why? Well, summing might not be necessary anymore from a technical perspective, but it’s still very much valid from a storytelling perspective, so to speak. Because the way you think of sound in film hasn’t changed. The green layer is still between 200-1000 audio tracks and many of them are layered components representing larger entities. For example, a massive door being shut could be delivered by sound designer b on predub ‘FX J’, consisting of different layers (creaking, handles, wood, bang) on a combination of mono and stereo, perhaps 5.0 channels. These tracks are stacked in a routing folder ‘FX J’, but fun fact: they are also sending to one of the FX reverbs that are not sitting in ‘FX J’ - For performance reasons not every FX predub can have it’s own reverb section. Arguably, as a mixer you can look at this door in two ways:
a) This door is a multitude of layers, I need to treat them all separately, to control and treat everything in all its complexity, also maybe largely overriding what a sound designer might have intended before me -> spill predub and mix with separate audio channels
b) It’s a door and I want to treat as such, find its place in the story, send it in its entirety to a reverb designed for the room, add more lower end by sending it to LFE and rolling a bit off the high end to place it a further back in the room -> work entirely on routing folder. Regardless of which you might prefer, it’s important to note, that large-scale theatrical mixes and other shows often start out by a number of temp mixes, where a first draft is laid out in a few days and for this as well as under-budgeted projects, mixing in groups is an absolute must.

Often a combination of the two will be used, not seldomly starting with broader strokes (b) like in temp mixes, rough mixes, premixes, then heading to more detailed work (a) - or the other way around. But regardless, for Atmos this will include toggling sounds into object channels here and there and essentially loosing any if not all of its parameters you established at the summing points: volume, EQ, reverb, other processing, anything that was added on the routing folders or later. So the logical workaround would be to at least use VCA faders for volume, in order for this information to not get lost when toggling to objects. Grouping inserts/sends on the other hand, is neither possible by VCAs nor routing folder / AUX. And even mix groups have their limitations, as grouping of plugins on multiple tracks with different channel orders is currently impossible regardless of whether they are multi-mono or multichannel (problem is addressed her: http://duc.avid.com/showthread.php?t=407165). For the layered door mentioned earlier, it cannot be EQ'ed in a grouped fashion, unless it's summed somewhere. So mixers currently end up mapping every predub twice on the console: once as a VCA for grouped volume automation and once as an AUX or routing folder for processing inserts and sends at least for everything heading to beds, which results in major limitations:
- 2 Faderstrips (VCA / routing folder) for a thing that should logically be one resulting in extremely large layouts
- Inserts and Sends on AUX / routing folder won’t control audio tracks routed to objects
- If audio tracks send to reverbs, AUX / Routing folder will only affect the dry signal, but not the wet return (unless every predub hat its own set of reverbs which performance forbids)
- In that scenario, also the volume fader of routing folders becomes virtually useless, as it also fades dry signal only
- A voice is allocated for every channel of every predub, which in Dolby Atmos can mean as much as 7.1.2 x 50 = 500 voices —> which seems futile as summing is really only intended at the violet layer: the dialog, music, effects (+ possibly other) bed

A VCA folder would solve all major problems in modern signal flows:
- allowing for toggling certain channels in and out of objects without changing their current sound properties in any way, by controling the source and not a sum
- volume automating large groups without changing the dry/wet ratio of reverbs
- keeping all tracks neatly organised on consoles with a single strip for each predub / subgroup
while keeping voices at a minimum
- allowing to seamlessly switch between treating predubs as an entity like a door (pan, eq, volume, sends entirely from VCA folder ‘FX D’) or as a group of separate sounds like thunders (determine volume, EQ and lfe send level from VCA folder ‘BG A’, then spilling and panning each thunder individually, some of them to objects, others to FX bed)
- endless possibilities and happiness

The functionality would look like this:
- Any audio track in the folder will automatically be slave to the VCA folder, with the exact same logic of current VCA faders (e.g. the fader of a slave can override the VCA level and so on)
- Plugins and Sends can be inserted on the VCA folder, but they don’t process an actual signal (since they don’t have a voice and no I/O), instead they only control plugins / sends on the identical slots of any underlying slaves in a grouped fashion (for example ‘unmute send b’ on VCA folder could send the entire group to a reverb b, while muting the same send on any underlying slave would override this command for the individual track)
- Even things like ‘object toggle’ could be performed from a VCA folder, sending every slave to their respective objects
- Pan of the VCA folder would group pan all underlying tracks (while panning slaves would override the master for the individual track and so on)

The reason why this is so relevant for an S6 subforum is simple: It’s what currently limits AVID consoles from being unlimited in function for Atmos mixes.
This and perhaps dynamic object routing and superb pec/dir metering of course :) (http://duc.avid.com/showthread.php?t=415256)
But I am sure it’s on the horizon! And I’m saying this as someone with 6 large-scale S6 setups in my facility.

If there are any question, I’m always happy to discuss.

Thanks + Best,
Gregor

[creativecontrol]

Thanks for the insightful suggestions. The concept of the VCA folder has certainly come up in numerous discussions. I will make sure your post is shared with product management.

best,


Jeff

[Rich Breen]

Gotta say, never understood why VCA behavior wasn't an option under Folder tracks - with a standard Folder track you end up with all these useless faders on the control surface taking up space but not usable for anything other than solo and mute. VCA Folders would save a lot of surface real-estate, in addition to addressing the OP's points.

[henningaround]

I too think basic folder tracks should also act as VCAs for their members. But this does not address the crucial feature Gregor is asking for. Right now the only way to handle EQ, Dynamics and Sends of a group of tracks is to route them into an AUX or Routing Folder and do it there. But that does not work for setups where routing into an AUX isn't an option like for Dolby Atmos.

[henningaround]

Well and at least the ability to also level the sends on a VCA for all its members in the same way you are able to level the main volume shouldn't be such a big deal.

[henningaround]

And the longer I think of it... if just every audio track would come with the standard AVID Channel Strip implemented and hard patched into first insert it should also be possible to be able to control it via a VCA the same way as volume automation.