George Lucas once said that “sound is 50% of the moviegoing experience.” Even so, less than 50% of cinema technologists actually understand the technology of sound. The science of color, picture distribution, and image projection has captured the minds of far more technologists than a bunch of digital samples of moving air. Unfortunately, this affects the quality of debate over how cinema sound should evolve.
One of the turnoffs of sound is the difficulty in defining quality. We may talk about “digital audio,” but all we’re really talking about is digital distribution of analog audio. Analog signals can be complex, and sound can be very complex. It’s probably fair to say that the means required to present a quality picture is better understood – or benefits from more agreement – than that to present quality sound. And if experts have a hard time agreeing on the subject, imagine what the audience must be thinking. A recent blog comment was spotted in which the writer of the article referred to Dolby Atmos as the latest 64.2 sound system. To which one of the commenters replied that he refrained from watching any movie with less than 74.4 channels of sound. These two statements precisely sum it up.
When describing an audio system as capable of 64 channels, it paints a picture in the minds of distributors that the average 8-channel audio track file must now grow by 8 times. Object-based sound, therefore, unchecked, could lead to file size inflation in digital cinema. Those companies wishing to put up smoke and mirrors like that perception. It says that audio compression is useful, which then opens the door to proprietary compression techniques…just one element in a list of elements that says that this mysterious technology can only be distributed using technology comprised of deep dark secrets.
In this month’s ISDCF meeting, some illuminating details about object-based sound came to light. Dolby proclaimed its intent to use Meridian Lossless compression in Atmos distributions. (Meridian Lossless is used in Dolby True HD for Blu Ray – secrets upon secrets required.) In the same meeting, Iosono proclaimed that a typical object-based mix without compression would occupy no more file space than a SMPTE DCP 16-channel audio track file. (No secrets required.) The rationale given was that sound objects have a short duration. While many sound objects may be moving about throughout the movie, they rarely occur at the same point in time. So while 64 channels may be allowed and utilized, a much smaller set of channels would be present in the audio track file at any one time. Thus, the average size of an uncompressed object-based audio track may not be any larger than a full set of 16-channels of uninterrupted sound in the SMPTE DCP audio track file.
This is an important revelation, underscoring yet another value point in why open distribution of object-based sound should be pursued, rather than allowing proprietary formats to flourish.
Another factor in representing object-based sound is describing the position of the sound object in space at any one time. This is a more interesting area to explore. In truth, much of this work has already been addressed by sound mixing technologies. Both Imm Sound and Iosono have probably put the most effort into describing and manipulating sound objects. A debate between these two as to how to best represent the sound object in the distribution channel would be beneficial to the industry. However, that’s unlikely to happen, as Imm Sound’s technologists are unlikely to be allowed to participate in such discussions now that Dolby bought (“conquered”) their company.
The issue of experts and collaboration is all the more important as three projects have been proposed in SMPTE for audio, not all of which nicely mesh. Dolby has proposed two audio-related projects, one for the standardization of a synchronization method for external audio playback systems, another for a standard and generic track file format in which their proprietary object-based audio format could be carried. A third project was proposed just prior to this month’s 21DC Technology Committee meeting by Iosono, for a study effort to explore a common B-chain for 3-D audio and a common distribution format.
Not having the benefit of discussion, the chair of 21DC postponed a decision on projects until a special meeting could be arranged for this purpose. To be continued.