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15 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
16 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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26 ***********************************************************************/
27
28 #ifdef HAVE_CONFIG_H
29 #include "config.h"
30 #endif
31
32 #include "SigProc_FIX.h"
33
34 /* Compute number of bits to right shift the sum of squares of a vector */
35 /* of int16s to make it fit in an int32 */
silk_sum_sqr_shift(opus_int32 * energy,opus_int * shift,const opus_int16 * x,opus_int len)36 void silk_sum_sqr_shift(
37 opus_int32 *energy, /* O Energy of x, after shifting to the right */
38 opus_int *shift, /* O Number of bits right shift applied to energy */
39 const opus_int16 *x, /* I Input vector */
40 opus_int len /* I Length of input vector */
41 )
42 {
43 opus_int i, shft;
44 opus_uint32 nrg_tmp;
45 opus_int32 nrg;
46
47 /* Do a first run with the maximum shift we could have. */
48 shft = 31-silk_CLZ32(len);
49 /* Let's be conservative with rounding and start with nrg=len. */
50 nrg = len;
51 for( i = 0; i < len - 1; i += 2 ) {
52 nrg_tmp = silk_SMULBB( x[ i ], x[ i ] );
53 nrg_tmp = silk_SMLABB_ovflw( nrg_tmp, x[ i + 1 ], x[ i + 1 ] );
54 nrg = (opus_int32)silk_ADD_RSHIFT_uint( nrg, nrg_tmp, shft );
55 }
56 if( i < len ) {
57 /* One sample left to process */
58 nrg_tmp = silk_SMULBB( x[ i ], x[ i ] );
59 nrg = (opus_int32)silk_ADD_RSHIFT_uint( nrg, nrg_tmp, shft );
60 }
61 silk_assert( nrg >= 0 );
62 /* Make sure the result will fit in a 32-bit signed integer with two bits
63 of headroom. */
64 shft = silk_max_32(0, shft+3 - silk_CLZ32(nrg));
65 nrg = 0;
66 for( i = 0 ; i < len - 1; i += 2 ) {
67 nrg_tmp = silk_SMULBB( x[ i ], x[ i ] );
68 nrg_tmp = silk_SMLABB_ovflw( nrg_tmp, x[ i + 1 ], x[ i + 1 ] );
69 nrg = (opus_int32)silk_ADD_RSHIFT_uint( nrg, nrg_tmp, shft );
70 }
71 if( i < len ) {
72 /* One sample left to process */
73 nrg_tmp = silk_SMULBB( x[ i ], x[ i ] );
74 nrg = (opus_int32)silk_ADD_RSHIFT_uint( nrg, nrg_tmp, shft );
75 }
76
77 silk_assert( nrg >= 0 );
78
79 /* Output arguments */
80 *shift = shft;
81 *energy = nrg;
82 }
83
84