summaryrefslogtreecommitdiff
path: root/silk/log2lin.c
diff options
context:
space:
mode:
authorJean-Marc Valin <jmvalin@jmvalin.ca>2011-09-16 01:16:53 -0700
committerJean-Marc Valin <jmvalin@jmvalin.ca>2011-09-16 01:16:53 -0700
commit1c2f5633d101c08b5ef8095a8682d3d52cbd952d (patch)
tree66f80e67f075db5fa5233759a89f475d8bedade2 /silk/log2lin.c
parentfb3a437c9dabb4aafe4a3927158161590ed745ab (diff)
downloadopus-1c2f5633d101c08b5ef8095a8682d3d52cbd952d.tar.gz
Removed all the silk_ prefixes in source file names (not symbols)
Diffstat (limited to 'silk/log2lin.c')
-rw-r--r--silk/log2lin.c54
1 files changed, 54 insertions, 0 deletions
diff --git a/silk/log2lin.c b/silk/log2lin.c
new file mode 100644
index 00000000..b49dd0a2
--- /dev/null
+++ b/silk/log2lin.c
@@ -0,0 +1,54 @@
+/***********************************************************************
+Copyright (c) 2006-2011, Skype Limited. All rights reserved.
+Redistribution and use in source and binary forms, with or without
+modification, (subject to the limitations in the disclaimer below)
+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 Skype Limited, nor the names of specific
+contributors, may be used to endorse or promote products derived from
+this software without specific prior written permission.
+NO EXPRESS OR IMPLIED LICENSES TO ANY PARTY'S PATENT RIGHTS ARE GRANTED
+BY THIS LICENSE. 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 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_RSHIFT( out, silk_MUL( out, silk_SMLAWB( frac_Q7, silk_MUL( 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_MUL( frac_Q7, 128 - frac_Q7 ), -174 ) );
+ }
+ return out;
+}