assuming RAND_MAX is around 1<<31, rand() >> 1 generates large numbers as
random volume data; these likely causes saturated sample values after
applying the volume function -- not a good test
I was looking at a log, and noticed the following lines:
I [pulseaudio] svolume_mmx.c: Initialising MMX optimized functions.
I [pulseaudio] remap_mmx.c: Initialising MMX optimized remappers.
I [pulseaudio] svolume_sse.c: Initialising SSE2 optimized functions.
I [pulseaudio] remap_sse.c: Initialising SSE2 optimized remappers.
I [pulseaudio] sconv_sse.c: Initialising SSE2 optimized conversions.
It seemed odd that some messages were somewhat precise in
what functionality was initialized, while the svolume
messages told me that they had initialized just "functions".
So I made the svolume log messages more precise to match the
sconv and remap messages.
This makes the volume tests run in two loops and print the minimum,
maximum and standard deviation of readings from the inner loop. This
makes it easier to reason out performance drops (i.e. algorithmic
problems vs. other system issues such as processor contention).
This adds volume scaling for 1- and 2-channel software volume scaling
using Orc. While testing the MMX and SSE backends on a Core2, I see an
~2x performance benefit over the hand-rolled MMX and SSE code. Since I
haven't been able to test on other architectures, the Orc code is only
used when MMX/SSE* is present. This can be changed in the future after
testing on AMD and ARM machines.
