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26 ***********************************************************************/
27
28 #ifdef HAVE_CONFIG_H
29 #include "config.h"
30 #endif
31
32 #include "main.h"
33
34 /* Quantize mid/side predictors */
silk_stereo_quant_pred(opus_int32 pred_Q13[],opus_int8 ix[2][3])35 void silk_stereo_quant_pred(
36 opus_int32 pred_Q13[], /* I/O Predictors (out: quantized) */
37 opus_int8 ix[ 2 ][ 3 ] /* O Quantization indices */
38 )
39 {
40 opus_int i, j, n;
41 opus_int32 low_Q13, step_Q13, lvl_Q13, err_min_Q13, err_Q13, quant_pred_Q13 = 0;
42
43 /* Quantize */
44 for( n = 0; n < 2; n++ ) {
45 /* Brute-force search over quantization levels */
46 err_min_Q13 = silk_int32_MAX;
47 for( i = 0; i < STEREO_QUANT_TAB_SIZE - 1; i++ ) {
48 low_Q13 = silk_stereo_pred_quant_Q13[ i ];
49 step_Q13 = silk_SMULWB( silk_stereo_pred_quant_Q13[ i + 1 ] - low_Q13,
50 SILK_FIX_CONST( 0.5 / STEREO_QUANT_SUB_STEPS, 16 ) );
51 for( j = 0; j < STEREO_QUANT_SUB_STEPS; j++ ) {
52 lvl_Q13 = silk_SMLABB( low_Q13, step_Q13, 2 * j + 1 );
53 err_Q13 = silk_abs( pred_Q13[ n ] - lvl_Q13 );
54 if( err_Q13 < err_min_Q13 ) {
55 err_min_Q13 = err_Q13;
56 quant_pred_Q13 = lvl_Q13;
57 ix[ n ][ 0 ] = i;
58 ix[ n ][ 1 ] = j;
59 } else {
60 /* Error increasing, so we're past the optimum */
61 goto done;
62 }
63 }
64 }
65 done:
66 ix[ n ][ 2 ] = silk_DIV32_16( ix[ n ][ 0 ], 3 );
67 ix[ n ][ 0 ] -= ix[ n ][ 2 ] * 3;
68 pred_Q13[ n ] = quant_pred_Q13;
69 }
70
71 /* Subtract second from first predictor (helps when actually applying these) */
72 pred_Q13[ 0 ] -= pred_Q13[ 1 ];
73 }
74