In the 90’s, multiple digital sound on film formats were introduced. Two of them carried 5.1 audio, and one of them 7.1 audio (notably, not the same speaker configuration as the 7.1DS format used today). All of them used a high degree of compression, which had an impact on the overall experience. In contrast, digital cinema carries a minimum of 16 uncompressed channels. Cinema sound took a holiday during the ‘oughts, but that holiday will be over at CinemaCon. On display will be Barco’s Auro3D, Imm Sound, IOSONO, and something new from Dolby.
The soundfield in cinema is being revisited. Surround speakers have been in use in cinema for a long time. Dolby promoted the “horseshoe” surround speaker layout in the late 70’s, which continues to be in use today in all but IMAX cinemas. 5.1 sound simply splits the horseshoe array into two channels. In contrast, the newer sound formats extend the surround concept to a multi-tiered array, not only surrounding the audience with sound, but allowing it to move over their heads. That, however, is where the similarities end.
Auro3D is a channel-based system offering 9.1 and 11.1 sound, and promoting itself as compatible with 5.1 distributions. Compatibility occurs by matrixing the additional sound channels into the 5.1 distribution. Each summed channel comprises the most significant 20 bits of a 24 bit audio track. The difference channel is squeezed into the remaining 4 bits using compression. Effectively, the difference channel is in the noise. When the track is played in a normal 5.1 auditorium, the compressed difference channel is masked by a combination of the noise of the system and the limited range of the D/A converters in the playback system’s media block. The system works, as long as the sound mixer’s decisions are compatible with the constraint of having upper and lower channels summed together, and as long as one is happy with the idea of less-than-24-bit audio.
Imm Sound is a spin-off from the University of Barcelona’s business incubator program. It takes a different approach from traditional cinema sound by divorcing itself from the channel-based approach. Instead, Imm Sound renders audio over the available set of speakers. It does this using proprietary algorithms. The multi-channel sound track is carried in a digital file that accompanies the digital composition, but is not contained within the 16-channel track file that is a standard feature of the digital composition. The company’s literature says the soundtrack is compressed using a lossless algorithm. The secondary sound track file is played in an Imm Sound processor, and synchronized with the movie using time code placed in the standard sound track of the composition. Imm Sound says it can accept 5.1 and 7.1 sound tracks, and render these over the auditorium’s speaker array. Imm Sound is operating today in 30 cinemas throughout the world. But not having heard it yet or fully understood how it reproduces normal sound tracks, it’s not possible to comment further.
IOSONO was perhaps the first system to have divorced itself from the concept of channel-based sound. IOSONO renders sound over a large array of speakers using a patented technique called Wave Field Synthesis, developed at Fraunhofer Institute in Germany by the same team responsible for the popular MP3 compression algorithm. Unlike Imm Sound, IOSONO compresses its multiple channels of sound objects in the 16 channels of audio available in the DCP. The sound track is decoded in the IOSONO cinema sound processor. Speaker counts range from 32 to 96 powered boxes, typically 60, including those behind the screen. IOSONO does not have an installed base of cinemas at this time, but its early systems have been installed in the Chinese theatre in Hollywood for several years. Newer systems will support multiple heights of sound, as with Imm Sound and Auro3D.
Dolby is about to announce it’s new system, which has not yet been disclosed to your author, and so cannot be described. The company is contracting with at least one 3rd party media block manufacturer for its in-projector media block, which is expected to be announced simultaneously. It would seem reasonable to assume that Dolby will decode its sound tracks using its in-projector media block. There appears to be a high expectation that Dolby’s system will be channel-based, and not rendered. One thing is certain: Dolby has plenty of cash to fuel a media frenzy. However, it if is producing a media block/sound system combo, Dolby is taking a risky approach. The company’s servers and media blocks have a reputation for being years behind the design curve, and its digital cinema servers now rank 4th in sales in the US. Sophisticated users in need of advanced sound integrate their digital cinema systems with a TMS, content, and key management systems. Dolby has a lot of work to do if the plan is to smoothly retrofit into select auditoriums.
With four interesting contenders now entering the so-called 3-D cinema audio space, one has to wonder how this will settle. Studios, paranoid about anti-trust lawsuits, are unlikely to pick winners and losers. So the battlefield for sound today is being fought at the movie director level. Every format is out to win a director’s heart, and is either now in a mixing room for a movie release, or working on a contract. But only so many mixes can be budgeted, making the most attractive system on the table the one whose digital audio workstation plugin is compatible with the most number of 3-D sound formats. The sharper companies are beginning to grasp this. Thus, the real battle of 3-D sound formats won’t be taking place at CinemaCon, but in the sound mixing room.
