lossyWAV 1.3.0 Development Thread
Reply #242 – 2011-01-25 09:52:23
Nick, now that you're at 1.2.2z RC1 so that 1.3.0 is ahead of us: what about cleaning up the option scenery which has evolved during the development process? My ideas on this as a whole (partially we talked about it already): a) with the explicit exclusion of the --limit strategy it would be good IMO to have only the --altpreset quality scheme and forget about the older one. The --altpreset scheme allows for a good audio quality when varying q in steps of 2.5 as you always did for the named presets. Also bitrate scales well for a step size of 2.5 with the --altpreset scheme. q should be allowed to be in the range -2.5 to 10 (or maybe -5 instead of -2.5, but -2.5 as a lower limit is more in line with the lossyWAV target properties IMO). b) analysis limit default should be the usual 16 kHz for q in the range q>=2.5, q<7.5. --limit should default to 15159 for q<2.5. --limit default should be 17 kHz or a little bit lower for q>=7.5. --limit should remain an explicit parameter to override the defaults. c) Adaptive noise shaping should be defaulted as it showed to be useful and doesn't break things. However there should be a switch to turn it off. So this is the opposite to today's behavior where it has to be explicitly switched on. As for the -A value I have no idea what is most appropriate. Today it defaults to 64 if I see this correctly. I used a value of 96, but that was only because you suggested this some day for trying out. Encoding speed using -A 96 is fine to me. My feeling (from very few experiments) is that resulting quality doesn't depend much on the -A value. So the FIR quality parameter should go IMO (with the -A option as adaptive noise shaping should be defaulted) and should be appropriately set internally. d) There should be named quality parameters which correspond to a -q stepsize of 2.5 used according to the default behavior as described by a) to c). Names can be similar to: - insane (equivalent to -q 10) - extreme (equivalent to -q 7.5) - standard (equivalent to -q 5) - economic (equivalent to -q 2.5) - portable (equivalent to -q 0) - superportable (equivalent to -q -2.5).