On Wed, Feb 12, 2014 at 09:49:25AM +0100, Niels Möller wrote: > The xll extension includes an hierachy of channel sets. I think I have > understood the general idea (the file can can provide a channel set > representing a downmix, followed by another channel set with the > information needed to undo the downmix and generate additional > channels), but not the fine details. [...] > > Does anyone (Kostya?) know what "the decoder shall traverse the channel > set hierarchy and count the number of channels within each channel set" > means? (I admit I'm a bit lazy here; the description makes my head spin, > and I haven't yet tried very hard to figure out what to do. So I ask, in > case someone else already have it all figured out).
Well, IIRC you can have some independent channel sets that are alternative to each other (i.e. different sets of surround channels). So one has to determine what channel sets you want to decode (i.e. one with channels 0-5 and one with channels 6-7) and count the number of channels in them. So for downmixing you have a matrix of all those previous channels to scale and mix. And yes, this is one of the best things in the standard. > And is there a distinction between "primary channel set" and "primary > channel group", or are they the same thing? Probably the same. > For the > http://samples.libav.org/A-codecs/DTS/dts/Master%20Audio%205.0%2096khz.dts > file, I get only a single channel set, with channels = 5, primar_ch_set > = 1 and downmix_type 1. So N = 5+1 = 6, and since the primary flag is > set, the final paragraph seems to apply, so M = 2 (downmix_type = 1 is a > downmix to stereo). I'm not going to to anything with the coefficients > now, but at least I think I know the number of bits (6*2*9) to skip. Seems right. > The testfile also has residual_encode = 0, which I think is a good case > to start with. > > And one other thing: If anyone has access to a known-good decoder for > dca xll, it would be great if I could get unpacked wav files > corresponding to the dts/"Master Audio"* sample files. Yes. _______________________________________________ libav-devel mailing list [email protected] https://lists.libav.org/mailman/listinfo/libav-devel
