Last month it was pointed out that Annex A of SMPTE 429-2 DCP Operational Constraints was missing a vital part needed for DCI compliance testing. SMPTE DCP-compliant audio does not spell out how to distribute the full complement of 16 channels of audio. However, DCI compliance testing requires this capability. In addition, the industry needs a method to play with creative new audio formats, such as the 7.1 format that Pixar and Disney want to distribute with “Toy Story 3.” This, plus a problem with the number of subtitle instances allowed, caused the formation of a new ad hoc group to propose amendments for the standard. Your author volunteered to chair it.
There is no doubt that audio in SMPTE DCP has made strides forward. The three fixed formats described in SMPTE 429-2 Annex A spell out how to deliver HI an VI-N assistive listening audio. But Annex A was originally designed to be a fallback, and not as the long term solution. The long term intent was to label each audio channel so that smart media blocks could direct each channel to a user-configured set of media block audio outputs. In effect, the principle of re-routing that now takes place when HI and VI-N audio is sent to media block outputs 15 and 16 could be applied to any audio channel. Dolby once proposed a patented method to do this…which died in committee. A non-patented method for audio channel labeling was also proposed that fit within the MXF paradigm. But that got nixed because those creating MXF broadcast standards also wanted to label audio, and didn’t like the idea of cinema people defining it. Out of this rabble a new committee was formed called 31FS-10. Words were said that the standard would be ready within a year, and a few years later here you are reading this.
But while all things audio may be a bit muddled, all is not lost. In a meeting this month, a draft document was put forward in 31FS-10 that appears to have wide support. With a little luck, it could go to ballot this year. It may take several years to wend its way into media blocks, but better late than never. In the meantime, we’ll have the 16-channel format to use.
Which brings up the question as to why the channel labeled format is needed at all? If one thinks about it, channel labels only have value if they can be dynamic in the fixed block of 16 distribution channels, and if more than 16 outputs are available from the media block. These conditions would allow sound to be redirected to different speakers as needed. But neither condition is likely to occur, and the idea of redirecting sound channels — turning off one speaker and turning on another — is cheap. If more than 16 channels are needed, then more than 16 channels should be delivered, which means we’re solving the wrong problem with audio labels.
While on the subject of solving wrong problems, a proposal was floating about within SMPTE to change the X-Curve equalization of sound rooms used in perhaps 150,000 screening rooms and auditoriums around the world for the past 30+ years. Some people simply have nothing better to do with their time. Fortunately, a few gray haired guys got involved and fashioned a revised proposed work statement to suggest improved measurement techniques and system design guidance, rather than throw out the whole kit. Politics prevented the new group from being formed under 20F-30 Film Sound, since it is chaired by Ioan Allen, the father of X-Curve. It’s a shame, really, because Ioan deserves to oversee this work. Instead, a Study Group was formed that has no parent group, called ST-SG Theatre B-Chain.
The new Study Group has all of the (now) gray haired people who originally made cinema audio work, including your author. In the first meeting, several people pointed out that science alone cannot determine when a room sounds good. It still takes the art of a good ear to tune a room. So your author quickly proposed that the first action was to outline the procedure for evaluating the results of new testing methods. It seemed an obvious step, knowing that no one involved had the ears of a 25 year old, and that some recruiting was needed. Interestingly, everyone liked the idea of establishing procedures. No one was ready to admit that recruitment was needed.