rockbox/lib/rbcodec/codecs/libopus/silk/log2lin.c
Nils Wallménius 580b307fd7 Sync opus codec to upstream git
Sync opus codec to upstream commit
02fed471a4568852d6618e041c4f2af0d7730ee2 (August 30 2013)

This brings in a lot of optimizations but also makes the diff
between our codec and the upstream much smaller as most of our
optimizations have been upstreamed or supeceded.

Speedups across the board for CELT mode files:

        64kbps      128kbps
H300    9.82MHz     15.48MHz
c200	4.86MHz     9.63MHz
fuze v1 10.32MHz    15.92MHz

For the silk mode test file (16kbps) arm targets get a speedup
of about 2MHz while the H300 is 7.8MHz slower, likely because it's
now using the pseudostack more rather than the real stack which
is in iram. Patches to get around that are upcomming.

Change-Id: Ifecf963e461c51ac42e09dac1e91bc4bc3b12fa3
2013-08-31 08:30:51 +02:00

56 lines
2.5 KiB
C

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#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "SigProc_FIX.h"
/* Approximation of 2^() (very close inverse of silk_lin2log()) */
/* Convert input to a linear scale */
opus_int32 silk_log2lin(
const opus_int32 inLog_Q7 /* I input on log scale */
)
{
opus_int32 out, frac_Q7;
if( inLog_Q7 < 0 ) {
return 0;
}
out = silk_LSHIFT( 1, silk_RSHIFT( inLog_Q7, 7 ) );
frac_Q7 = inLog_Q7 & 0x7F;
if( inLog_Q7 < 2048 ) {
/* Piece-wise parabolic approximation */
out = silk_ADD_RSHIFT32( out, silk_MUL( out, silk_SMLAWB( frac_Q7, silk_SMULBB( frac_Q7, 128 - frac_Q7 ), -174 ) ), 7 );
} else {
/* Piece-wise parabolic approximation */
out = silk_MLA( out, silk_RSHIFT( out, 7 ), silk_SMLAWB( frac_Q7, silk_SMULBB( frac_Q7, 128 - frac_Q7 ), -174 ) );
}
return out;
}