Audio ProcessingTo move to fully digital cinema places a greater importance on the cinema processor. It is the processor that will determine the quality of the sound reproduction and also the types of content that you can display.
Two of the major trends impacting the cinema industry today are the transition from movies created and distributed on film to full digital and the requirement for cinema to support alternative content to take advantage of attractive new revenue streams.
With the DCI standard mandating the use of uncompressed digital audio files to ensure the sound reaches the cinema exactly as it left the mixing desk, the role of audio processor has changed. The audio processor no longer has to seamlessly convert analog inputs into a digital format for tuning and preparation for output. Instead, it can concentrate on ensuring that the sound that fills the cinema is as close to the original intention of the film makers and sound engineers as possible.
This means providing the sound professional in the cinema with the ability to create a sound stage that is natural and immersive to their entire audience. Something that has been notoriously difficult in cinema theaters that can be extremely ‘flat’ and whose design was often driven by the desire to optimize the viewing experience with little regard for the sound.
Of course, the need to support alternative content means that not just one sound stage needs to be created but a whole series. Each content type – whether movie, sporting event or live concert – has its own sound dynamics. With sound, one size definitely doesn’t fit all. The sound engineer must create the ideal sound stage for each content type and be able to save and restore each quickly so that the room doesn’t have to be retuned each time the content changes.
The result of these developments is need for a far greater granularity of control over digital audio. This goes way beyond 1/3 octave and parameter equalization or bass and speaker control. It means being able to control all aspects of the sound and manipulate that sound to provide a high quality listening experience that overcomes the ‘eccentricities’ of the room.
The latest generation of digital audio processors for cinema are delivering this level of control .
There are a range of capabilities that every audio processor should have:
Inputs and outputs
Although the cinema industry is moving to digital, there is still a need for both digital and analog inputs and outputs – even if it’s only to work with your existing speaker arrangement. An audio processor with 8 channels of inputs and outputs will accommodate a small range of content types and the traditional 5.1 surround sound arrangement is used by most cinemas today. However, it is limiting. If you consider some approaches to delivering more advanced surround sound require twice as many output channels as input then a 16 channel audio processor is likely to be a more suitable choice.
Delivering the largest possible sweet spot with a cinema theater is always challenging. Rooms and loudspeakers distort sound in both the frequency and time domains. It takes sophisticated measurement and calculation to ensure that you can produce a localization of sound events for every listener. This requires complete control over all elements involved in sound reproduction to provide outstanding clarity of the stereo sound image. Often the goal will not be to remove any distortion but work with different elements of room optimization to produce psychoacoustic effects that makes the listening environment sound as close to the real world as possible.
Equalization and beyond
Parametric and 1/3 octave equalization has long been central to audio processing solutions. They remain an important component of any processor. These are now being augmented by features that deliver a more granular control of the sound. The modern audio processor should come with filters to deliver impulse response control, magnitude response control, channel gain control, and phase inversion control. Individual treble and bass controls can be provided on a ‘per channel’ basis. Variable delays on the sound delivered to different output channels allows for the audio to be coordinated to create a consistent experience throughout the theater.
The digital audio processor that you select is only one component of the entire digital cinema system and also needs to integrate with other back office systems. You want to be able to select ‘best of breed’ solutions from each part of your system. The audio processor should offer complete interoperability and be able to deliver a degree of future-proofing to accommodate other advances in digital cinema technology.