I spent some time with the MPEG ALS reference code, and applied several code and algorithmic optimizations, as well as builds with different compilers. The result seems to be a speedup between 0 and 200%, depending on the exact settings used.
I did not use the included lpc_adapt.o, but instead wrote my own algorithms for adaptive determination of the LPC order. It seems to work well, but it is slightly inferior in ratio compared to the shipped one, but it compensates that a bit by being faster.
If you are playing with ALS the following settings seem interesting from a speed/ratio point of view:
"Fast": -o5
"Default":
"High": -a -o30
"Extra High": -a -b -o50
Settings like -t, -p and -z1, -z2 and z3 don't really provide a seizable gain for large increases in encoding and decoding time. However, for maximal compression -z3 seems to be best.
Binaries can be downloaded at
http://sjeng.org/ftp/lossless/
[Edit: there's a single binary per arechitecture now]
For Intel machines mp4als_intel should be best. I did not benchmark on AMD's yet.
Please note that patents may apply to MPEG ALS, and that you may need a patent license for legal use of this program.
