remap: Add special remapping case which just re-arranges channels
Input channels may just be copied to output channels, no mixing; this
avoids the generic (slow) matrix remapping code in cases where channels
are dropped or reordered.
This makes use of the remap struct state introduced earlier.
on Intel Core i7-870 @ 2.93 GHz (GCC 4.6, 64-bit):
Checking special remap (s16, stereo rearrange)
func: 126117 usec (avg: 1261.17, min = 1150, max = 2111, stddev = 117.332).
orig: 190509 usec (avg: 1905.09, min = 1807, max = 2402, stddev = 100.984).
Checking special remap (float, stereo rearrange)
func: 194329 usec (avg: 1943.29, min = 1876, max = 2127, stddev = 64.3486).
orig: 205263 usec (avg: 2052.63, min = 2005, max = 2452, stddev = 70.177).
Checking special remap (s16, 4-channel rearrange)
func: 278754 usec (avg: 2787.54, min = 2719, max = 3093, stddev = 78.22).
orig: 383885 usec (avg: 3838.85, min = 3634, max = 4121, stddev = 128.522).
Checking special remap (float, 4-channel rearrange)
func: 312429 usec (avg: 3124.29, min = 3017, max = 3498, stddev = 120.127).
orig: 388198 usec (avg: 3881.98, min = 3768, max = 4655, stddev = 138.441).
on ARM Cortex-A8 (TI OMAP3 DM3730 @ 1GHz) (Linaro GCC 4.6):
Checking special remap (s16, stereo rearrange)
func:
1204647 usec (avg: 12046.5, min = 10406, max = 25451, stddev = 2491.9).
orig:
1660311 usec (avg: 16603.1, min = 14740, max = 20416, stddev = 1708.07).
Checking special remap (float, stereo rearrange)
func:
1391392 usec (avg: 13913.9, min = 12207, max = 28260, stddev = 2238.12).
orig:
9246707 usec (avg: 92467.1, min = 87525, max = 125611, stddev = 5494.64).
Checking special remap (s16, 4-channel rearrange)
func:
2540225 usec (avg: 25402.2, min = 16937, max = 68268, stddev = 10786.7).
orig:
3319852 usec (avg: 33198.5, min = 29571, max = 36957, stddev = 1250.39).
Checking special remap (float, 4-channel rearrange)
func:
3024414 usec (avg: 30244.1, min = 26153, max = 58105, stddev = 4506.01).
orig:
12643624 usec (avg: 126436, min = 120575, max = 159088, stddev = 5519.28).
benchmark code will be posted as follow-up patches
Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>