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26 ***********************************************************************/
27
28 #ifdef HAVE_CONFIG_H
29 #include "config.h"
30 #endif
31
32 #include "main.h"
33 #include "stack_alloc.h"
34
35 /* Convert Left/Right stereo signal to adaptive Mid/Side representation */
silk_stereo_LR_to_MS(stereo_enc_state * state,opus_int16 x1[],opus_int16 x2[],opus_int8 ix[2][3],opus_int8 * mid_only_flag,opus_int32 mid_side_rates_bps[],opus_int32 total_rate_bps,opus_int prev_speech_act_Q8,opus_int toMono,opus_int fs_kHz,opus_int frame_length)36 void silk_stereo_LR_to_MS(
37 stereo_enc_state *state, /* I/O State */
38 opus_int16 x1[], /* I/O Left input signal, becomes mid signal */
39 opus_int16 x2[], /* I/O Right input signal, becomes side signal */
40 opus_int8 ix[ 2 ][ 3 ], /* O Quantization indices */
41 opus_int8 *mid_only_flag, /* O Flag: only mid signal coded */
42 opus_int32 mid_side_rates_bps[], /* O Bitrates for mid and side signals */
43 opus_int32 total_rate_bps, /* I Total bitrate */
44 opus_int prev_speech_act_Q8, /* I Speech activity level in previous frame */
45 opus_int toMono, /* I Last frame before a stereo->mono transition */
46 opus_int fs_kHz, /* I Sample rate (kHz) */
47 opus_int frame_length /* I Number of samples */
48 )
49 {
50 opus_int n, is10msFrame, denom_Q16, delta0_Q13, delta1_Q13;
51 opus_int32 sum, diff, smooth_coef_Q16, pred_Q13[ 2 ], pred0_Q13, pred1_Q13;
52 opus_int32 LP_ratio_Q14, HP_ratio_Q14, frac_Q16, frac_3_Q16, min_mid_rate_bps, width_Q14, w_Q24, deltaw_Q24;
53 VARDECL( opus_int16, side );
54 VARDECL( opus_int16, LP_mid );
55 VARDECL( opus_int16, HP_mid );
56 VARDECL( opus_int16, LP_side );
57 VARDECL( opus_int16, HP_side );
58 opus_int16 *mid = &x1[ -2 ];
59 SAVE_STACK;
60
61 ALLOC( side, frame_length + 2, opus_int16 );
62 /* Convert to basic mid/side signals */
63 for( n = 0; n < frame_length + 2; n++ ) {
64 sum = x1[ n - 2 ] + (opus_int32)x2[ n - 2 ];
65 diff = x1[ n - 2 ] - (opus_int32)x2[ n - 2 ];
66 mid[ n ] = (opus_int16)silk_RSHIFT_ROUND( sum, 1 );
67 side[ n ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( diff, 1 ) );
68 }
69
70 /* Buffering */
71 silk_memcpy( mid, state->sMid, 2 * sizeof( opus_int16 ) );
72 silk_memcpy( side, state->sSide, 2 * sizeof( opus_int16 ) );
73 silk_memcpy( state->sMid, &mid[ frame_length ], 2 * sizeof( opus_int16 ) );
74 silk_memcpy( state->sSide, &side[ frame_length ], 2 * sizeof( opus_int16 ) );
75
76 /* LP and HP filter mid signal */
77 ALLOC( LP_mid, frame_length, opus_int16 );
78 ALLOC( HP_mid, frame_length, opus_int16 );
79 for( n = 0; n < frame_length; n++ ) {
80 sum = silk_RSHIFT_ROUND( silk_ADD_LSHIFT( mid[ n ] + mid[ n + 2 ], mid[ n + 1 ], 1 ), 2 );
81 LP_mid[ n ] = sum;
82 HP_mid[ n ] = mid[ n + 1 ] - sum;
83 }
84
85 /* LP and HP filter side signal */
86 ALLOC( LP_side, frame_length, opus_int16 );
87 ALLOC( HP_side, frame_length, opus_int16 );
88 for( n = 0; n < frame_length; n++ ) {
89 sum = silk_RSHIFT_ROUND( silk_ADD_LSHIFT( side[ n ] + side[ n + 2 ], side[ n + 1 ], 1 ), 2 );
90 LP_side[ n ] = sum;
91 HP_side[ n ] = side[ n + 1 ] - sum;
92 }
93
94 /* Find energies and predictors */
95 is10msFrame = frame_length == 10 * fs_kHz;
96 smooth_coef_Q16 = is10msFrame ?
97 SILK_FIX_CONST( STEREO_RATIO_SMOOTH_COEF / 2, 16 ) :
98 SILK_FIX_CONST( STEREO_RATIO_SMOOTH_COEF, 16 );
99 smooth_coef_Q16 = silk_SMULWB( silk_SMULBB( prev_speech_act_Q8, prev_speech_act_Q8 ), smooth_coef_Q16 );
100
101 pred_Q13[ 0 ] = silk_stereo_find_predictor( &LP_ratio_Q14, LP_mid, LP_side, &state->mid_side_amp_Q0[ 0 ], frame_length, smooth_coef_Q16 );
102 pred_Q13[ 1 ] = silk_stereo_find_predictor( &HP_ratio_Q14, HP_mid, HP_side, &state->mid_side_amp_Q0[ 2 ], frame_length, smooth_coef_Q16 );
103 /* Ratio of the norms of residual and mid signals */
104 frac_Q16 = silk_SMLABB( HP_ratio_Q14, LP_ratio_Q14, 3 );
105 frac_Q16 = silk_min( frac_Q16, SILK_FIX_CONST( 1, 16 ) );
106
107 /* Determine bitrate distribution between mid and side, and possibly reduce stereo width */
108 total_rate_bps -= is10msFrame ? 1200 : 600; /* Subtract approximate bitrate for coding stereo parameters */
109 if( total_rate_bps < 1 ) {
110 total_rate_bps = 1;
111 }
112 min_mid_rate_bps = silk_SMLABB( 2000, fs_kHz, 900 );
113 silk_assert( min_mid_rate_bps < 32767 );
114 /* Default bitrate distribution: 8 parts for Mid and (5+3*frac) parts for Side. so: mid_rate = ( 8 / ( 13 + 3 * frac ) ) * total_ rate */
115 frac_3_Q16 = silk_MUL( 3, frac_Q16 );
116 mid_side_rates_bps[ 0 ] = silk_DIV32_varQ( total_rate_bps, SILK_FIX_CONST( 8 + 5, 16 ) + frac_3_Q16, 16+3 );
117 /* If Mid bitrate below minimum, reduce stereo width */
118 if( mid_side_rates_bps[ 0 ] < min_mid_rate_bps ) {
119 mid_side_rates_bps[ 0 ] = min_mid_rate_bps;
120 mid_side_rates_bps[ 1 ] = total_rate_bps - mid_side_rates_bps[ 0 ];
121 /* width = 4 * ( 2 * side_rate - min_rate ) / ( ( 1 + 3 * frac ) * min_rate ) */
122 width_Q14 = silk_DIV32_varQ( silk_LSHIFT( mid_side_rates_bps[ 1 ], 1 ) - min_mid_rate_bps,
123 silk_SMULWB( SILK_FIX_CONST( 1, 16 ) + frac_3_Q16, min_mid_rate_bps ), 14+2 );
124 width_Q14 = silk_LIMIT( width_Q14, 0, SILK_FIX_CONST( 1, 14 ) );
125 } else {
126 mid_side_rates_bps[ 1 ] = total_rate_bps - mid_side_rates_bps[ 0 ];
127 width_Q14 = SILK_FIX_CONST( 1, 14 );
128 }
129
130 /* Smoother */
131 state->smth_width_Q14 = (opus_int16)silk_SMLAWB( state->smth_width_Q14, width_Q14 - state->smth_width_Q14, smooth_coef_Q16 );
132
133 /* At very low bitrates or for inputs that are nearly amplitude panned, switch to panned-mono coding */
134 *mid_only_flag = 0;
135 if( toMono ) {
136 /* Last frame before stereo->mono transition; collapse stereo width */
137 width_Q14 = 0;
138 pred_Q13[ 0 ] = 0;
139 pred_Q13[ 1 ] = 0;
140 silk_stereo_quant_pred( pred_Q13, ix );
141 } else if( state->width_prev_Q14 == 0 &&
142 ( 8 * total_rate_bps < 13 * min_mid_rate_bps || silk_SMULWB( frac_Q16, state->smth_width_Q14 ) < SILK_FIX_CONST( 0.05, 14 ) ) )
143 {
144 /* Code as panned-mono; previous frame already had zero width */
145 /* Scale down and quantize predictors */
146 pred_Q13[ 0 ] = silk_RSHIFT( silk_SMULBB( state->smth_width_Q14, pred_Q13[ 0 ] ), 14 );
147 pred_Q13[ 1 ] = silk_RSHIFT( silk_SMULBB( state->smth_width_Q14, pred_Q13[ 1 ] ), 14 );
148 silk_stereo_quant_pred( pred_Q13, ix );
149 /* Collapse stereo width */
150 width_Q14 = 0;
151 pred_Q13[ 0 ] = 0;
152 pred_Q13[ 1 ] = 0;
153 mid_side_rates_bps[ 0 ] = total_rate_bps;
154 mid_side_rates_bps[ 1 ] = 0;
155 *mid_only_flag = 1;
156 } else if( state->width_prev_Q14 != 0 &&
157 ( 8 * total_rate_bps < 11 * min_mid_rate_bps || silk_SMULWB( frac_Q16, state->smth_width_Q14 ) < SILK_FIX_CONST( 0.02, 14 ) ) )
158 {
159 /* Transition to zero-width stereo */
160 /* Scale down and quantize predictors */
161 pred_Q13[ 0 ] = silk_RSHIFT( silk_SMULBB( state->smth_width_Q14, pred_Q13[ 0 ] ), 14 );
162 pred_Q13[ 1 ] = silk_RSHIFT( silk_SMULBB( state->smth_width_Q14, pred_Q13[ 1 ] ), 14 );
163 silk_stereo_quant_pred( pred_Q13, ix );
164 /* Collapse stereo width */
165 width_Q14 = 0;
166 pred_Q13[ 0 ] = 0;
167 pred_Q13[ 1 ] = 0;
168 } else if( state->smth_width_Q14 > SILK_FIX_CONST( 0.95, 14 ) ) {
169 /* Full-width stereo coding */
170 silk_stereo_quant_pred( pred_Q13, ix );
171 width_Q14 = SILK_FIX_CONST( 1, 14 );
172 } else {
173 /* Reduced-width stereo coding; scale down and quantize predictors */
174 pred_Q13[ 0 ] = silk_RSHIFT( silk_SMULBB( state->smth_width_Q14, pred_Q13[ 0 ] ), 14 );
175 pred_Q13[ 1 ] = silk_RSHIFT( silk_SMULBB( state->smth_width_Q14, pred_Q13[ 1 ] ), 14 );
176 silk_stereo_quant_pred( pred_Q13, ix );
177 width_Q14 = state->smth_width_Q14;
178 }
179
180 /* Make sure to keep on encoding until the tapered output has been transmitted */
181 if( *mid_only_flag == 1 ) {
182 state->silent_side_len += frame_length - STEREO_INTERP_LEN_MS * fs_kHz;
183 if( state->silent_side_len < LA_SHAPE_MS * fs_kHz ) {
184 *mid_only_flag = 0;
185 } else {
186 /* Limit to avoid wrapping around */
187 state->silent_side_len = 10000;
188 }
189 } else {
190 state->silent_side_len = 0;
191 }
192
193 if( *mid_only_flag == 0 && mid_side_rates_bps[ 1 ] < 1 ) {
194 mid_side_rates_bps[ 1 ] = 1;
195 mid_side_rates_bps[ 0 ] = silk_max_int( 1, total_rate_bps - mid_side_rates_bps[ 1 ]);
196 }
197
198 /* Interpolate predictors and subtract prediction from side channel */
199 pred0_Q13 = -state->pred_prev_Q13[ 0 ];
200 pred1_Q13 = -state->pred_prev_Q13[ 1 ];
201 w_Q24 = silk_LSHIFT( state->width_prev_Q14, 10 );
202 denom_Q16 = silk_DIV32_16( (opus_int32)1 << 16, STEREO_INTERP_LEN_MS * fs_kHz );
203 delta0_Q13 = -silk_RSHIFT_ROUND( silk_SMULBB( pred_Q13[ 0 ] - state->pred_prev_Q13[ 0 ], denom_Q16 ), 16 );
204 delta1_Q13 = -silk_RSHIFT_ROUND( silk_SMULBB( pred_Q13[ 1 ] - state->pred_prev_Q13[ 1 ], denom_Q16 ), 16 );
205 deltaw_Q24 = silk_LSHIFT( silk_SMULWB( width_Q14 - state->width_prev_Q14, denom_Q16 ), 10 );
206 for( n = 0; n < STEREO_INTERP_LEN_MS * fs_kHz; n++ ) {
207 pred0_Q13 += delta0_Q13;
208 pred1_Q13 += delta1_Q13;
209 w_Q24 += deltaw_Q24;
210 sum = silk_LSHIFT( silk_ADD_LSHIFT( mid[ n ] + mid[ n + 2 ], mid[ n + 1 ], 1 ), 9 ); /* Q11 */
211 sum = silk_SMLAWB( silk_SMULWB( w_Q24, side[ n + 1 ] ), sum, pred0_Q13 ); /* Q8 */
212 sum = silk_SMLAWB( sum, silk_LSHIFT( (opus_int32)mid[ n + 1 ], 11 ), pred1_Q13 ); /* Q8 */
213 x2[ n - 1 ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( sum, 8 ) );
214 }
215
216 pred0_Q13 = -pred_Q13[ 0 ];
217 pred1_Q13 = -pred_Q13[ 1 ];
218 w_Q24 = silk_LSHIFT( width_Q14, 10 );
219 for( n = STEREO_INTERP_LEN_MS * fs_kHz; n < frame_length; n++ ) {
220 sum = silk_LSHIFT( silk_ADD_LSHIFT( mid[ n ] + mid[ n + 2 ], mid[ n + 1 ], 1 ), 9 ); /* Q11 */
221 sum = silk_SMLAWB( silk_SMULWB( w_Q24, side[ n + 1 ] ), sum, pred0_Q13 ); /* Q8 */
222 sum = silk_SMLAWB( sum, silk_LSHIFT( (opus_int32)mid[ n + 1 ], 11 ), pred1_Q13 ); /* Q8 */
223 x2[ n - 1 ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( sum, 8 ) );
224 }
225 state->pred_prev_Q13[ 0 ] = (opus_int16)pred_Q13[ 0 ];
226 state->pred_prev_Q13[ 1 ] = (opus_int16)pred_Q13[ 1 ];
227 state->width_prev_Q14 = (opus_int16)width_Q14;
228 RESTORE_STACK;
229 }
230