Recently I wrote about the AAC channel model. Since then I tested a variety of real world broken files (synthetically recreated) with the reference decoder, faad, WinAMP, iTunes, and the Microsoft Windows 7 Decoder. I've placed the results in the multimedia wiki. I can't seem to get the CSS right to display it here.
Looking at the results of the other decoders I managed to fix bad_concat while removing special hacks for streams like elem_id0 with a new approach in FFmpeg. FFmpeg now treats streams with PCEs according to the letter of the channel configuration in the PCE. For streams lacking a PCE, element instance tags are now ignored and channels are treated purely positionally.
One other thing worth noting is that I couldn't make iTunes produce Parametric Stereo effects on any of the seven signalling streams from CT. Supposedly iTunes has supported PS since version 9.2. Perhaps it is due to the use of pure upsampling SBR.
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