the Digital Cinema Naming Convention still depicts Audio type '20= LtRt Stereo'. However, 'LtRt' is common technical term for matrix encoded audio. Now we have seen a few classic titles using matrix encoded audio in DCPs. While some few cinema audio processors offer the ability to apply matrix decoding to incoming AES audio, there have been earlier discussions on the ISDCF mailing list with the outcome that matrix encoded audio should not be used in DCPs.
Even those cinema processors with support for matrix decoding need special setup or wiring to do it - which usually is beyond staff scope in daily operations, even for those cinemas dedicated to 'classic titles'. And even those cinemas with capable processors may not have the necessary means to switch between 5.1/7.1 to matrix decoding automatically within playlists.
At the same time, those titles using matrix encoded audio so far did not use any special marking to indicate this. Or they were simply assuming the DCN to be formally correct with the 20=LtRt audio type.
Sometimes it looks as if the distributor didn't even know about this aspect of the DCP: 'It's an old movie - it's plain stereo!'.
So, the question is: Should the DCN exclude LtRt explicitly, or should a special audio designator be introduced, separating 20-Stereo from 20-LtRt? I think excluding LtRt from the DCN won't stop studios issuing such DCPs.
While we probably all agree that stereo mixes are not suitable for cinema presentation, they do exist and will exist in the future, and there may well be suitable situations to use them - e.g. music only audiotracks. Most surround soundtracks will contain stereo-only passages to a certain extent anyway
What do you think? I contacted Jerry about a year ago already, and he said he would correct the issue for the next DCN version review. Unfortunately, the version number didn't change since then
Jerry, is this still on your To-Do for 9.x?
Regards - Carsten