Film Standards: Auxiliary Channels
These are extra channels, usually representing effects or different output paths such as headphone monitors, to which other designated channels can be routed. 'Aux channels' in film mixing usually get used to access expensive hardware reverbs or any number of digital or analogue effects units.
One important difference to note here between film and game mixing is that film mixing is done 'offline' in a studio, meaning the film is mixed, and then the mix is mastered or 'printed', meaning all the automation and effects are bounced down to a single final master version of the soundtrack to accompany the picture.
In a game, the mixing happens at run-time in a software engine and is happening every time the player actually plays the game. Because video game mixing can only ever rely on the software effects and DSP that ship with the game, software-based aux channels may be used to send the sound from a particular channel to a software reverb, also running in memory in real-time.
An aux send value in video game mixing software is very useful in being able to tune the amount of signal that is sent to a reverb, for 3D sounds for example, and tuning these values definitely falls under the category of 'mixing'.
Film Standards: Automation
Automation is an essentially linear media concept, but it can be mapped over to interactive realms in various forms. Put simply, automation is the recording of changes in the values of parameters of a particular channel over time, and as such can be used to record and play back volume or panning changes on a given channel strip. Going from one snapshot to another over time, could be considered a low resolution form of automation.
If during a cutscene, for example, you wanted to change the level of the in-game ambience that is playing in the background at a particular moment, you could install a different mixer snapshot on a given frame of the movie which changes the value of the ambient in-game sound volume.
Mixer snapshots themselves also form a cornerstone of interactive mixing technology, allowing a preset of channel and bus levels to be installed and un-installed to coincide with generic or specific in-game events.
These mixer snapshots can be used to perform a whole range of mixing functions, from simple ducking, to complete change of sonic perspectives by manipulating pitch and distance fall-off values. They also form a fundamental part of the interactive mixing technology in today's third-party and proprietary tool-sets, and will be explored in more detail later.
Film Standards: Standardization
Reference listening levels of 85dB are well established in motion picture mixing. This is a very important distinction from the music industry, which has no standards, and as a result music levels are completely varied from record to record.
The standard listening reference level in movies means, at least theoretically, that the movie is mixed at the same volume that it will be exhibited in the theatre, so the mixers can replicate that environment and make the best decisions about the sound levels based on their ears in that situation. It is because of these standards that we do not get motion picture soundtracks of wildly differing output levels.
Current video game output levels are much closer to the varied and sporadically different output levels of the music industry than those of film, so much so that a recommendation for a common reference listening level is clearly needed. My own thoughts are that this level should be in line with other 'home entertainment' media, such as TV shows or DVD remixes of movies and there already exists a standard reference listening level of 79dB for these media.
It makes sense that games, being a home entertainment medium, should adopt these output levels in order to be on a par with DVD movies (which like theatrical 85dB mixes, are generally in line with the 79dB output level).
This also makes sense because DVDs and Blu-ray discs are more often than not played back on the very same consoles on which we play our games. The goal is that the consumer should not be constantly having to change the volume of their TV set or surround sound system to make up for the differences in levels from game to movie, movie to game and even game to game.