1 files changed, 76 insertions, 0 deletions
diff --git a/drivers/opus/silk/sigm_Q15.c b/drivers/opus/silk/sigm_Q15.c
new file mode 100644
index 0000000000..2df5b9695c
--- /dev/null
+++ b/drivers/opus/silk/sigm_Q15.c
@@ -0,0 +1,76 @@
+/***********************************************************************
+Copyright (c) 2006-2011, Skype Limited. All rights reserved.
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions
+are met:
+- Redistributions of source code must retain the above copyright notice,
+this list of conditions and the following disclaimer.
+- Redistributions in binary form must reproduce the above copyright
+notice, this list of conditions and the following disclaimer in the
+documentation and/or other materials provided with the distribution.
+- Neither the name of Internet Society, IETF or IETF Trust, nor the
+names of specific contributors, may be used to endorse or promote
+products derived from this software without specific prior written
+permission.
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGE.
+***********************************************************************/
+
+#ifdef OPUS_HAVE_CONFIG_H
+#include "opus_config.h"
+#endif
+
+/* Approximate sigmoid function */
+
+#include "SigProc_FIX.h"
+
+/* fprintf(1, '%d, ', round(1024 * ([1 ./ (1 + exp(-(1:5))), 1] - 1 ./ (1 + exp(-(0:5)))))); */
+static const opus_int32 sigm_LUT_slope_Q10[ 6 ] = {
+    237, 153, 73, 30, 12, 7
+};
+/* fprintf(1, '%d, ', round(32767 * 1 ./ (1 + exp(-(0:5))))); */
+static const opus_int32 sigm_LUT_pos_Q15[ 6 ] = {
+    16384, 23955, 28861, 31213, 32178, 32548
+};
+/* fprintf(1, '%d, ', round(32767 * 1 ./ (1 + exp((0:5))))); */
+static const opus_int32 sigm_LUT_neg_Q15[ 6 ] = {
+    16384, 8812, 3906, 1554, 589, 219
+};
+
+opus_int silk_sigm_Q15(
+    opus_int                    in_Q5               /* I                                                                */
+)
+{
+    opus_int ind;
+
+    if( in_Q5 < 0 ) {
+        /* Negative input */
+        in_Q5 = -in_Q5;
+        if( in_Q5 >= 6 * 32 ) {
+            return 0;        /* Clip */
+        } else {
+            /* Linear interpolation of look up table */
+            ind = silk_RSHIFT( in_Q5, 5 );
+            return( sigm_LUT_neg_Q15[ ind ] - silk_SMULBB( sigm_LUT_slope_Q10[ ind ], in_Q5 & 0x1F ) );
+        }
+    } else {
+        /* Positive input */
+        if( in_Q5 >= 6 * 32 ) {
+            return 32767;        /* clip */
+        } else {
+            /* Linear interpolation of look up table */
+            ind = silk_RSHIFT( in_Q5, 5 );
+            return( sigm_LUT_pos_Q15[ ind ] + silk_SMULBB( sigm_LUT_slope_Q10[ ind ], in_Q5 & 0x1F ) );
+        }
+    }
+}
+