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26 ***********************************************************************/
27 
28 
29 /**************************************************************/
30 /* Compute noise shaping coefficients and initial gain values */
31 /**************************************************************/
32 #define OVERRIDE_silk_noise_shape_analysis_FIX
33 
silk_noise_shape_analysis_FIX(silk_encoder_state_FIX * psEnc,silk_encoder_control_FIX * psEncCtrl,const opus_int16 * pitch_res,const opus_int16 * x,int arch)34 void silk_noise_shape_analysis_FIX(
35     silk_encoder_state_FIX          *psEnc,                                 /* I/O  Encoder state FIX                                                           */
36     silk_encoder_control_FIX        *psEncCtrl,                             /* I/O  Encoder control FIX                                                         */
37     const opus_int16                *pitch_res,                             /* I    LPC residual from pitch analysis                                            */
38     const opus_int16                *x,                                     /* I    Input signal [ frame_length + la_shape ]                                    */
39     int                              arch                                   /* I    Run-time architecture                                                       */
40 )
41 {
42     silk_shape_state_FIX *psShapeSt = &psEnc->sShape;
43     opus_int     k, i, nSamples, Qnrg, b_Q14, warping_Q16, scale = 0;
44     opus_int32   SNR_adj_dB_Q7, HarmBoost_Q16, HarmShapeGain_Q16, Tilt_Q16, tmp32;
45     opus_int32   nrg, pre_nrg_Q30, log_energy_Q7, log_energy_prev_Q7, energy_variation_Q7;
46     opus_int32   delta_Q16, BWExp1_Q16, BWExp2_Q16, gain_mult_Q16, gain_add_Q16, strength_Q16, b_Q8;
47     opus_int32   auto_corr[     MAX_SHAPE_LPC_ORDER + 1 ];
48     opus_int32   refl_coef_Q16[ MAX_SHAPE_LPC_ORDER ];
49     opus_int32   AR1_Q24[       MAX_SHAPE_LPC_ORDER ];
50     opus_int32   AR2_Q24[       MAX_SHAPE_LPC_ORDER ];
51     VARDECL( opus_int16, x_windowed );
52     const opus_int16 *x_ptr, *pitch_res_ptr;
53     SAVE_STACK;
54 
55     /* Point to start of first LPC analysis block */
56     x_ptr = x - psEnc->sCmn.la_shape;
57 
58     /****************/
59     /* GAIN CONTROL */
60     /****************/
61     SNR_adj_dB_Q7 = psEnc->sCmn.SNR_dB_Q7;
62 
63     /* Input quality is the average of the quality in the lowest two VAD bands */
64     psEncCtrl->input_quality_Q14 = ( opus_int )silk_RSHIFT( (opus_int32)psEnc->sCmn.input_quality_bands_Q15[ 0 ]
65         + psEnc->sCmn.input_quality_bands_Q15[ 1 ], 2 );
66 
67     /* Coding quality level, between 0.0_Q0 and 1.0_Q0, but in Q14 */
68     psEncCtrl->coding_quality_Q14 = silk_RSHIFT( silk_sigm_Q15( silk_RSHIFT_ROUND( SNR_adj_dB_Q7 -
69         SILK_FIX_CONST( 20.0, 7 ), 4 ) ), 1 );
70 
71     /* Reduce coding SNR during low speech activity */
72     if( psEnc->sCmn.useCBR == 0 ) {
73         b_Q8 = SILK_FIX_CONST( 1.0, 8 ) - psEnc->sCmn.speech_activity_Q8;
74         b_Q8 = silk_SMULWB( silk_LSHIFT( b_Q8, 8 ), b_Q8 );
75         SNR_adj_dB_Q7 = silk_SMLAWB( SNR_adj_dB_Q7,
76             silk_SMULBB( SILK_FIX_CONST( -BG_SNR_DECR_dB, 7 ) >> ( 4 + 1 ), b_Q8 ),                                       /* Q11*/
77             silk_SMULWB( SILK_FIX_CONST( 1.0, 14 ) + psEncCtrl->input_quality_Q14, psEncCtrl->coding_quality_Q14 ) );     /* Q12*/
78     }
79 
80     if( psEnc->sCmn.indices.signalType == TYPE_VOICED ) {
81         /* Reduce gains for periodic signals */
82         SNR_adj_dB_Q7 = silk_SMLAWB( SNR_adj_dB_Q7, SILK_FIX_CONST( HARM_SNR_INCR_dB, 8 ), psEnc->LTPCorr_Q15 );
83     } else {
84         /* For unvoiced signals and low-quality input, adjust the quality slower than SNR_dB setting */
85         SNR_adj_dB_Q7 = silk_SMLAWB( SNR_adj_dB_Q7,
86             silk_SMLAWB( SILK_FIX_CONST( 6.0, 9 ), -SILK_FIX_CONST( 0.4, 18 ), psEnc->sCmn.SNR_dB_Q7 ),
87             SILK_FIX_CONST( 1.0, 14 ) - psEncCtrl->input_quality_Q14 );
88     }
89 
90     /*************************/
91     /* SPARSENESS PROCESSING */
92     /*************************/
93     /* Set quantizer offset */
94     if( psEnc->sCmn.indices.signalType == TYPE_VOICED ) {
95         /* Initially set to 0; may be overruled in process_gains(..) */
96         psEnc->sCmn.indices.quantOffsetType = 0;
97         psEncCtrl->sparseness_Q8 = 0;
98     } else {
99         /* Sparseness measure, based on relative fluctuations of energy per 2 milliseconds */
100         nSamples = silk_LSHIFT( psEnc->sCmn.fs_kHz, 1 );
101         energy_variation_Q7 = 0;
102         log_energy_prev_Q7  = 0;
103         pitch_res_ptr = pitch_res;
104         for( k = 0; k < silk_SMULBB( SUB_FRAME_LENGTH_MS, psEnc->sCmn.nb_subfr ) / 2; k++ ) {
105             silk_sum_sqr_shift( &nrg, &scale, pitch_res_ptr, nSamples );
106             nrg += silk_RSHIFT( nSamples, scale );           /* Q(-scale)*/
107 
108             log_energy_Q7 = silk_lin2log( nrg );
109             if( k > 0 ) {
110                 energy_variation_Q7 += silk_abs( log_energy_Q7 - log_energy_prev_Q7 );
111             }
112             log_energy_prev_Q7 = log_energy_Q7;
113             pitch_res_ptr += nSamples;
114         }
115 
116         psEncCtrl->sparseness_Q8 = silk_RSHIFT( silk_sigm_Q15( silk_SMULWB( energy_variation_Q7 -
117             SILK_FIX_CONST( 5.0, 7 ), SILK_FIX_CONST( 0.1, 16 ) ) ), 7 );
118 
119         /* Set quantization offset depending on sparseness measure */
120         if( psEncCtrl->sparseness_Q8 > SILK_FIX_CONST( SPARSENESS_THRESHOLD_QNT_OFFSET, 8 ) ) {
121             psEnc->sCmn.indices.quantOffsetType = 0;
122         } else {
123             psEnc->sCmn.indices.quantOffsetType = 1;
124         }
125 
126         /* Increase coding SNR for sparse signals */
127         SNR_adj_dB_Q7 = silk_SMLAWB( SNR_adj_dB_Q7, SILK_FIX_CONST( SPARSE_SNR_INCR_dB, 15 ), psEncCtrl->sparseness_Q8 - SILK_FIX_CONST( 0.5, 8 ) );
128     }
129 
130     /*******************************/
131     /* Control bandwidth expansion */
132     /*******************************/
133     /* More BWE for signals with high prediction gain */
134     strength_Q16 = silk_SMULWB( psEncCtrl->predGain_Q16, SILK_FIX_CONST( FIND_PITCH_WHITE_NOISE_FRACTION, 16 ) );
135     BWExp1_Q16 = BWExp2_Q16 = silk_DIV32_varQ( SILK_FIX_CONST( BANDWIDTH_EXPANSION, 16 ),
136         silk_SMLAWW( SILK_FIX_CONST( 1.0, 16 ), strength_Q16, strength_Q16 ), 16 );
137     delta_Q16  = silk_SMULWB( SILK_FIX_CONST( 1.0, 16 ) - silk_SMULBB( 3, psEncCtrl->coding_quality_Q14 ),
138         SILK_FIX_CONST( LOW_RATE_BANDWIDTH_EXPANSION_DELTA, 16 ) );
139     BWExp1_Q16 = silk_SUB32( BWExp1_Q16, delta_Q16 );
140     BWExp2_Q16 = silk_ADD32( BWExp2_Q16, delta_Q16 );
141     /* BWExp1 will be applied after BWExp2, so make it relative */
142     BWExp1_Q16 = silk_DIV32_16( silk_LSHIFT( BWExp1_Q16, 14 ), silk_RSHIFT( BWExp2_Q16, 2 ) );
143 
144     if( psEnc->sCmn.warping_Q16 > 0 ) {
145         /* Slightly more warping in analysis will move quantization noise up in frequency, where it's better masked */
146         warping_Q16 = silk_SMLAWB( psEnc->sCmn.warping_Q16, (opus_int32)psEncCtrl->coding_quality_Q14, SILK_FIX_CONST( 0.01, 18 ) );
147     } else {
148         warping_Q16 = 0;
149     }
150 
151     /********************************************/
152     /* Compute noise shaping AR coefs and gains */
153     /********************************************/
154     ALLOC( x_windowed, psEnc->sCmn.shapeWinLength, opus_int16 );
155     for( k = 0; k < psEnc->sCmn.nb_subfr; k++ ) {
156         /* Apply window: sine slope followed by flat part followed by cosine slope */
157         opus_int shift, slope_part, flat_part;
158         flat_part = psEnc->sCmn.fs_kHz * 3;
159         slope_part = silk_RSHIFT( psEnc->sCmn.shapeWinLength - flat_part, 1 );
160 
161         silk_apply_sine_window( x_windowed, x_ptr, 1, slope_part );
162         shift = slope_part;
163         silk_memcpy( x_windowed + shift, x_ptr + shift, flat_part * sizeof(opus_int16) );
164         shift += flat_part;
165         silk_apply_sine_window( x_windowed + shift, x_ptr + shift, 2, slope_part );
166 
167         /* Update pointer: next LPC analysis block */
168         x_ptr += psEnc->sCmn.subfr_length;
169 
170         if( psEnc->sCmn.warping_Q16 > 0 ) {
171             /* Calculate warped auto correlation */
172             silk_warped_autocorrelation_FIX( auto_corr, &scale, x_windowed, warping_Q16, psEnc->sCmn.shapeWinLength, psEnc->sCmn.shapingLPCOrder, arch );
173         } else {
174             /* Calculate regular auto correlation */
175             silk_autocorr( auto_corr, &scale, x_windowed, psEnc->sCmn.shapeWinLength, psEnc->sCmn.shapingLPCOrder + 1, arch );
176         }
177 
178         /* Add white noise, as a fraction of energy */
179         auto_corr[0] = silk_ADD32( auto_corr[0], silk_max_32( silk_SMULWB( silk_RSHIFT( auto_corr[ 0 ], 4 ),
180             SILK_FIX_CONST( SHAPE_WHITE_NOISE_FRACTION, 20 ) ), 1 ) );
181 
182         /* Calculate the reflection coefficients using schur */
183         nrg = silk_schur64( refl_coef_Q16, auto_corr, psEnc->sCmn.shapingLPCOrder );
184         silk_assert( nrg >= 0 );
185 
186         /* Convert reflection coefficients to prediction coefficients */
187         silk_k2a_Q16( AR2_Q24, refl_coef_Q16, psEnc->sCmn.shapingLPCOrder );
188 
189         Qnrg = -scale;          /* range: -12...30*/
190         silk_assert( Qnrg >= -12 );
191         silk_assert( Qnrg <=  30 );
192 
193         /* Make sure that Qnrg is an even number */
194         if( Qnrg & 1 ) {
195             Qnrg -= 1;
196             nrg >>= 1;
197         }
198 
199         tmp32 = silk_SQRT_APPROX( nrg );
200         Qnrg >>= 1;             /* range: -6...15*/
201 
202         psEncCtrl->Gains_Q16[ k ] = (silk_LSHIFT32( silk_LIMIT( (tmp32), silk_RSHIFT32( silk_int32_MIN, (16 - Qnrg) ), \
203                             silk_RSHIFT32( silk_int32_MAX, (16 - Qnrg) ) ), (16 - Qnrg) ));
204 
205         if( psEnc->sCmn.warping_Q16 > 0 ) {
206             /* Adjust gain for warping */
207             gain_mult_Q16 = warped_gain( AR2_Q24, warping_Q16, psEnc->sCmn.shapingLPCOrder );
208             silk_assert( psEncCtrl->Gains_Q16[ k ] >= 0 );
209             if ( silk_SMULWW( silk_RSHIFT_ROUND( psEncCtrl->Gains_Q16[ k ], 1 ), gain_mult_Q16 ) >= ( silk_int32_MAX >> 1 ) ) {
210                psEncCtrl->Gains_Q16[ k ] = silk_int32_MAX;
211             } else {
212                psEncCtrl->Gains_Q16[ k ] = silk_SMULWW( psEncCtrl->Gains_Q16[ k ], gain_mult_Q16 );
213             }
214         }
215 
216         /* Bandwidth expansion for synthesis filter shaping */
217         silk_bwexpander_32( AR2_Q24, psEnc->sCmn.shapingLPCOrder, BWExp2_Q16 );
218 
219         /* Compute noise shaping filter coefficients */
220         silk_memcpy( AR1_Q24, AR2_Q24, psEnc->sCmn.shapingLPCOrder * sizeof( opus_int32 ) );
221 
222         /* Bandwidth expansion for analysis filter shaping */
223         silk_assert( BWExp1_Q16 <= SILK_FIX_CONST( 1.0, 16 ) );
224         silk_bwexpander_32( AR1_Q24, psEnc->sCmn.shapingLPCOrder, BWExp1_Q16 );
225 
226         /* Ratio of prediction gains, in energy domain */
227         pre_nrg_Q30 = silk_LPC_inverse_pred_gain_Q24( AR2_Q24, psEnc->sCmn.shapingLPCOrder, arch );
228         nrg         = silk_LPC_inverse_pred_gain_Q24( AR1_Q24, psEnc->sCmn.shapingLPCOrder, arch );
229 
230         /*psEncCtrl->GainsPre[ k ] = 1.0f - 0.7f * ( 1.0f - pre_nrg / nrg ) = 0.3f + 0.7f * pre_nrg / nrg;*/
231         pre_nrg_Q30 = silk_LSHIFT32( silk_SMULWB( pre_nrg_Q30, SILK_FIX_CONST( 0.7, 15 ) ), 1 );
232         psEncCtrl->GainsPre_Q14[ k ] = ( opus_int ) SILK_FIX_CONST( 0.3, 14 ) + silk_DIV32_varQ( pre_nrg_Q30, nrg, 14 );
233 
234         /* Convert to monic warped prediction coefficients and limit absolute values */
235         limit_warped_coefs( AR2_Q24, AR1_Q24, warping_Q16, SILK_FIX_CONST( 3.999, 24 ), psEnc->sCmn.shapingLPCOrder );
236 
237         /* Convert from Q24 to Q13 and store in int16 */
238         for( i = 0; i < psEnc->sCmn.shapingLPCOrder; i++ ) {
239             psEncCtrl->AR1_Q13[ k * MAX_SHAPE_LPC_ORDER + i ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( AR1_Q24[ i ], 11 ) );
240             psEncCtrl->AR2_Q13[ k * MAX_SHAPE_LPC_ORDER + i ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( AR2_Q24[ i ], 11 ) );
241         }
242     }
243 
244     /*****************/
245     /* Gain tweaking */
246     /*****************/
247     /* Increase gains during low speech activity and put lower limit on gains */
248     gain_mult_Q16 = silk_log2lin( -silk_SMLAWB( -SILK_FIX_CONST( 16.0, 7 ), SNR_adj_dB_Q7, SILK_FIX_CONST( 0.16, 16 ) ) );
249     gain_add_Q16  = silk_log2lin(  silk_SMLAWB(  SILK_FIX_CONST( 16.0, 7 ), SILK_FIX_CONST( MIN_QGAIN_DB, 7 ), SILK_FIX_CONST( 0.16, 16 ) ) );
250     silk_assert( gain_mult_Q16 > 0 );
251     for( k = 0; k < psEnc->sCmn.nb_subfr; k++ ) {
252         psEncCtrl->Gains_Q16[ k ] = silk_SMULWW( psEncCtrl->Gains_Q16[ k ], gain_mult_Q16 );
253         silk_assert( psEncCtrl->Gains_Q16[ k ] >= 0 );
254         psEncCtrl->Gains_Q16[ k ] = silk_ADD_POS_SAT32( psEncCtrl->Gains_Q16[ k ], gain_add_Q16 );
255     }
256 
257     gain_mult_Q16 = SILK_FIX_CONST( 1.0, 16 ) + silk_RSHIFT_ROUND( silk_MLA( SILK_FIX_CONST( INPUT_TILT, 26 ),
258         psEncCtrl->coding_quality_Q14, SILK_FIX_CONST( HIGH_RATE_INPUT_TILT, 12 ) ), 10 );
259     for( k = 0; k < psEnc->sCmn.nb_subfr; k++ ) {
260         psEncCtrl->GainsPre_Q14[ k ] = silk_SMULWB( gain_mult_Q16, psEncCtrl->GainsPre_Q14[ k ] );
261     }
262 
263     /************************************************/
264     /* Control low-frequency shaping and noise tilt */
265     /************************************************/
266     /* Less low frequency shaping for noisy inputs */
267     strength_Q16 = silk_MUL( SILK_FIX_CONST( LOW_FREQ_SHAPING, 4 ), silk_SMLAWB( SILK_FIX_CONST( 1.0, 12 ),
268         SILK_FIX_CONST( LOW_QUALITY_LOW_FREQ_SHAPING_DECR, 13 ), psEnc->sCmn.input_quality_bands_Q15[ 0 ] - SILK_FIX_CONST( 1.0, 15 ) ) );
269     strength_Q16 = silk_RSHIFT( silk_MUL( strength_Q16, psEnc->sCmn.speech_activity_Q8 ), 8 );
270     if( psEnc->sCmn.indices.signalType == TYPE_VOICED ) {
271         /* Reduce low frequencies quantization noise for periodic signals, depending on pitch lag */
272         /*f = 400; freqz([1, -0.98 + 2e-4 * f], [1, -0.97 + 7e-4 * f], 2^12, Fs); axis([0, 1000, -10, 1])*/
273         opus_int fs_kHz_inv = silk_DIV32_16( SILK_FIX_CONST( 0.2, 14 ), psEnc->sCmn.fs_kHz );
274         for( k = 0; k < psEnc->sCmn.nb_subfr; k++ ) {
275             b_Q14 = fs_kHz_inv + silk_DIV32_16( SILK_FIX_CONST( 3.0, 14 ), psEncCtrl->pitchL[ k ] );
276             /* Pack two coefficients in one int32 */
277             psEncCtrl->LF_shp_Q14[ k ]  = silk_LSHIFT( SILK_FIX_CONST( 1.0, 14 ) - b_Q14 - silk_SMULWB( strength_Q16, b_Q14 ), 16 );
278             psEncCtrl->LF_shp_Q14[ k ] |= (opus_uint16)( b_Q14 - SILK_FIX_CONST( 1.0, 14 ) );
279         }
280         silk_assert( SILK_FIX_CONST( HARM_HP_NOISE_COEF, 24 ) < SILK_FIX_CONST( 0.5, 24 ) ); /* Guarantees that second argument to SMULWB() is within range of an opus_int16*/
281         Tilt_Q16 = - SILK_FIX_CONST( HP_NOISE_COEF, 16 ) -
282             silk_SMULWB( SILK_FIX_CONST( 1.0, 16 ) - SILK_FIX_CONST( HP_NOISE_COEF, 16 ),
283                 silk_SMULWB( SILK_FIX_CONST( HARM_HP_NOISE_COEF, 24 ), psEnc->sCmn.speech_activity_Q8 ) );
284     } else {
285         b_Q14 = silk_DIV32_16( 21299, psEnc->sCmn.fs_kHz ); /* 1.3_Q0 = 21299_Q14*/
286         /* Pack two coefficients in one int32 */
287         psEncCtrl->LF_shp_Q14[ 0 ]  = silk_LSHIFT( SILK_FIX_CONST( 1.0, 14 ) - b_Q14 -
288             silk_SMULWB( strength_Q16, silk_SMULWB( SILK_FIX_CONST( 0.6, 16 ), b_Q14 ) ), 16 );
289         psEncCtrl->LF_shp_Q14[ 0 ] |= (opus_uint16)( b_Q14 - SILK_FIX_CONST( 1.0, 14 ) );
290         for( k = 1; k < psEnc->sCmn.nb_subfr; k++ ) {
291             psEncCtrl->LF_shp_Q14[ k ] = psEncCtrl->LF_shp_Q14[ 0 ];
292         }
293         Tilt_Q16 = -SILK_FIX_CONST( HP_NOISE_COEF, 16 );
294     }
295 
296     /****************************/
297     /* HARMONIC SHAPING CONTROL */
298     /****************************/
299     /* Control boosting of harmonic frequencies */
300     HarmBoost_Q16 = silk_SMULWB( silk_SMULWB( SILK_FIX_CONST( 1.0, 17 ) - silk_LSHIFT( psEncCtrl->coding_quality_Q14, 3 ),
301         psEnc->LTPCorr_Q15 ), SILK_FIX_CONST( LOW_RATE_HARMONIC_BOOST, 16 ) );
302 
303     /* More harmonic boost for noisy input signals */
304     HarmBoost_Q16 = silk_SMLAWB( HarmBoost_Q16,
305         SILK_FIX_CONST( 1.0, 16 ) - silk_LSHIFT( psEncCtrl->input_quality_Q14, 2 ), SILK_FIX_CONST( LOW_INPUT_QUALITY_HARMONIC_BOOST, 16 ) );
306 
307     if( USE_HARM_SHAPING && psEnc->sCmn.indices.signalType == TYPE_VOICED ) {
308         /* More harmonic noise shaping for high bitrates or noisy input */
309         HarmShapeGain_Q16 = silk_SMLAWB( SILK_FIX_CONST( HARMONIC_SHAPING, 16 ),
310                 SILK_FIX_CONST( 1.0, 16 ) - silk_SMULWB( SILK_FIX_CONST( 1.0, 18 ) - silk_LSHIFT( psEncCtrl->coding_quality_Q14, 4 ),
311                 psEncCtrl->input_quality_Q14 ), SILK_FIX_CONST( HIGH_RATE_OR_LOW_QUALITY_HARMONIC_SHAPING, 16 ) );
312 
313         /* Less harmonic noise shaping for less periodic signals */
314         HarmShapeGain_Q16 = silk_SMULWB( silk_LSHIFT( HarmShapeGain_Q16, 1 ),
315             silk_SQRT_APPROX( silk_LSHIFT( psEnc->LTPCorr_Q15, 15 ) ) );
316     } else {
317         HarmShapeGain_Q16 = 0;
318     }
319 
320     /*************************/
321     /* Smooth over subframes */
322     /*************************/
323     for( k = 0; k < MAX_NB_SUBFR; k++ ) {
324         psShapeSt->HarmBoost_smth_Q16 =
325             silk_SMLAWB( psShapeSt->HarmBoost_smth_Q16,     HarmBoost_Q16     - psShapeSt->HarmBoost_smth_Q16,     SILK_FIX_CONST( SUBFR_SMTH_COEF, 16 ) );
326         psShapeSt->HarmShapeGain_smth_Q16 =
327             silk_SMLAWB( psShapeSt->HarmShapeGain_smth_Q16, HarmShapeGain_Q16 - psShapeSt->HarmShapeGain_smth_Q16, SILK_FIX_CONST( SUBFR_SMTH_COEF, 16 ) );
328         psShapeSt->Tilt_smth_Q16 =
329             silk_SMLAWB( psShapeSt->Tilt_smth_Q16,          Tilt_Q16          - psShapeSt->Tilt_smth_Q16,          SILK_FIX_CONST( SUBFR_SMTH_COEF, 16 ) );
330 
331         psEncCtrl->HarmBoost_Q14[ k ]     = ( opus_int )silk_RSHIFT_ROUND( psShapeSt->HarmBoost_smth_Q16,     2 );
332         psEncCtrl->HarmShapeGain_Q14[ k ] = ( opus_int )silk_RSHIFT_ROUND( psShapeSt->HarmShapeGain_smth_Q16, 2 );
333         psEncCtrl->Tilt_Q14[ k ]          = ( opus_int )silk_RSHIFT_ROUND( psShapeSt->Tilt_smth_Q16,          2 );
334     }
335     RESTORE_STACK;
336 }
337