sum_sqr_shift.c 3.7 KB

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  15. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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  27. #ifdef HAVE_CONFIG_H
  28. #include "config.h"
  29. #endif
  30. #include "SigProc_FIX.h"
  31. /* Compute number of bits to right shift the sum of squares of a vector */
  32. /* of int16s to make it fit in an int32 */
  33. void silk_sum_sqr_shift(
  34. opus_int32 *energy, /* O Energy of x, after shifting to the right */
  35. opus_int *shift, /* O Number of bits right shift applied to energy */
  36. const opus_int16 *x, /* I Input vector */
  37. opus_int len /* I Length of input vector */
  38. )
  39. {
  40. opus_int i, shft;
  41. opus_uint32 nrg_tmp;
  42. opus_int32 nrg;
  43. /* Do a first run with the maximum shift we could have. */
  44. shft = 31-silk_CLZ32(len);
  45. /* Let's be conservative with rounding and start with nrg=len. */
  46. nrg = len;
  47. for( i = 0; i < len - 1; i += 2 ) {
  48. nrg_tmp = silk_SMULBB( x[ i ], x[ i ] );
  49. nrg_tmp = silk_SMLABB_ovflw( nrg_tmp, x[ i + 1 ], x[ i + 1 ] );
  50. nrg = (opus_int32)silk_ADD_RSHIFT_uint( nrg, nrg_tmp, shft );
  51. }
  52. if( i < len ) {
  53. /* One sample left to process */
  54. nrg_tmp = silk_SMULBB( x[ i ], x[ i ] );
  55. nrg = (opus_int32)silk_ADD_RSHIFT_uint( nrg, nrg_tmp, shft );
  56. }
  57. silk_assert( nrg >= 0 );
  58. /* Make sure the result will fit in a 32-bit signed integer with two bits
  59. of headroom. */
  60. shft = silk_max_32(0, shft+3 - silk_CLZ32(nrg));
  61. nrg = 0;
  62. for( i = 0 ; i < len - 1; i += 2 ) {
  63. nrg_tmp = silk_SMULBB( x[ i ], x[ i ] );
  64. nrg_tmp = silk_SMLABB_ovflw( nrg_tmp, x[ i + 1 ], x[ i + 1 ] );
  65. nrg = (opus_int32)silk_ADD_RSHIFT_uint( nrg, nrg_tmp, shft );
  66. }
  67. if( i < len ) {
  68. /* One sample left to process */
  69. nrg_tmp = silk_SMULBB( x[ i ], x[ i ] );
  70. nrg = (opus_int32)silk_ADD_RSHIFT_uint( nrg, nrg_tmp, shft );
  71. }
  72. silk_assert( nrg >= 0 );
  73. /* Output arguments */
  74. *shift = shft;
  75. *energy = nrg;
  76. }