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comparison libgsmhr1/sp_dec.c @ 603:27df1cef042c

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libgsmhr1: put aToRc() only in dec_func.c This function was originally static in sp_dec.c, but now it is needed both in sp_dec.c and in dec_func.c shared decoder+encoder functions. Solution: give it intermodule linkage, and let it reside in dec_func.c only.
author Mychaela Falconia <falcon@freecalypso.org>
date Thu, 04 Dec 2025 19:05:38 +0000
parents c7c03231002d
children
comparison
equal deleted inserted replaced
602:72cdae602d6e 603:27df1cef042c
100 Shortword pswDirectFormCoefOut[]); 100 Shortword pswDirectFormCoefOut[]);
101 101
102 static Shortword lagDecode(Shortword swDeltaLag, Shortword *pswLastLag, 102 static Shortword lagDecode(Shortword swDeltaLag, Shortword *pswLastLag,
103 Shortword subfrm); 103 Shortword subfrm);
104 104
105 static short aToRc(Shortword swAshift, Shortword pswAin[],
106 Shortword pswRc[]);
107
108 static Shortword agcGain(Shortword pswStateCurr[], 105 static Shortword agcGain(Shortword pswStateCurr[],
109 struct NormSw snsInSigEnergy, 106 struct NormSw snsInSigEnergy,
110 Shortword swEngyRShft); 107 Shortword swEngyRShft);
111 108
112 static void lookupVq(Shortword pswVqCodeWds[], Shortword pswRCOut[]); 109 static void lookupVq(Shortword pswVqCodeWds[], Shortword pswRCOut[]);
148 #define AFSHIFT 2 /* number of right shifts to be 145 #define AFSHIFT 2 /* number of right shifts to be
149 * applied to the autocorrelation 146 * applied to the autocorrelation
150 * sequence in aFlatRcDp */ 147 * sequence in aFlatRcDp */
151 148
152 #define PCM_MASK 0xfff8 /* 16 to 13 bit linear PCM mask */ 149 #define PCM_MASK 0xfff8 /* 16 to 13 bit linear PCM mask */
153
154 /***************************************************************************
155 *
156 * FUNCTION NAME: aToRc
157 *
158 * PURPOSE:
159 *
160 * This subroutine computes a vector of reflection coefficients, given
161 * an input vector of direct form LPC filter coefficients.
162 *
163 * INPUTS:
164 *
165 * NP
166 * order of the LPC filter (global constant)
167 *
168 * swAshift
169 * The number of right shifts applied externally
170 * to the direct form filter coefficients.
171 *
172 * pswAin[0:NP-1]
173 * The input vector of direct form LPC filter
174 * coefficients.
175 *
176 * OUTPUTS:
177 *
178 * pswRc[0:NP-1]
179 * Array containing the reflection coefficients.
180 *
181 * RETURN VALUE:
182 *
183 * siUnstableFlt
184 * If stable reflection coefficients 0, 1 if unstable.
185 *
186 *
187 * DESCRIPTION:
188 *
189 * This function performs the conversion from direct form
190 * coefficients to reflection coefficients. It is used in a_sst()
191 * and interpolateCheck(). In a_sst() reflection coefficients used
192 * as a transitional data format. aToRc() is used for this
193 * conversion.
194 *
195 * When performing interpolation, a stability check must be
196 * performed. interpolateCheck() does this by calling aToRc().
197 *
198 * First coefficients are shifted down by iAshift. NP, the filter
199 * order is 10. The a's and rc's each have NP elements in them. An
200 * elaborate algorithm description can be found on page 443, of
201 * "Digital Processing of Speech Signals" by L.R. Rabiner and R.W.
202 * Schafer; Prentice-Hall; Englewood Cliffs, NJ (USA). 1978.
203 *
204 * REFERENCES: Sub_Clause 4.1.6, and 4.2.3 of GSM Recomendation 06.20
205 *
206 * KEYWORDS: reflectioncoefficients, parcors, conversion, atorc, ks, as
207 * KEYWORDS: parcorcoefficients, lpc, flat, vectorquantization
208 *
209 *************************************************************************/
210
211 static short aToRc(Shortword swAshift, Shortword pswAin[],
212 Shortword pswRc[])
213 {
214
215 /*_________________________________________________________________________
216 | |
217 | Constants |
218 |_________________________________________________________________________|
219 */
220
221 /*_________________________________________________________________________
222 | |
223 | Automatic Variables |
224 |_________________________________________________________________________|
225 */
226
227 Shortword pswTmpSpace[NP],
228 pswASpace[NP],
229 swNormShift,
230 swActShift,
231 swNormProd,
232 swRcOverE,
233 swDiv,
234 *pswSwap,
235 *pswTmp,
236 *pswA;
237
238 Longword L_temp;
239
240 short int siUnstableFlt,
241 i,
242 j; /* Loop control variables */
243
244 /*_________________________________________________________________________
245 | |
246 | Executable Code |
247 |_________________________________________________________________________|
248 */
249
250 /* Initialize starting addresses for temporary buffers */
251 /*-----------------------------------------------------*/
252
253 pswA = pswASpace;
254 pswTmp = pswTmpSpace;
255
256 /* Copy the direct form filter coefficients to a temporary array */
257 /*---------------------------------------------------------------*/
258
259 for (i = 0; i < NP; i++)
260 {
261 pswA[i] = pswAin[i];
262 }
263
264 /* Initialize the flag for filter stability check */
265 /*------------------------------------------------*/
266
267 siUnstableFlt = 0;
268
269 /* Start computation of the reflection coefficients, Rc[9],...,Rc[1] */
270 /*-------------------------------------------------------------------*/
271
272 for (i = NP - 1; i >= 1; i--)
273 {
274
275 pswRc[i] = shl(pswA[i], swAshift); /* write Rc[i] to output array */
276
277 /* Check the stability of i-th reflection coefficient */
278 /*----------------------------------------------------*/
279
280 siUnstableFlt = siUnstableFlt | isSwLimit(pswRc[i]);
281
282 /* Precompute intermediate variables for needed for the computation */
283 /* of direct form filter of order i-1 */
284 /*------------------------------------------------------------------*/
285
286 if (sub(pswRc[i], SW_MIN) == 0)
287 {
288 siUnstableFlt = 1;
289 swRcOverE = 0;
290 swDiv = 0;
291 swActShift = 2;
292 }
293 else
294 {
295 L_temp = LW_MAX; /* Load ~1.0 into accum */
296 L_temp = L_msu(L_temp, pswRc[i], pswRc[i]); /* 1.-Rc[i]*Rc[i] */
297 swNormShift = norm_l(L_temp);
298 L_temp = L_shl(L_temp, swNormShift);
299 swNormProd = extract_h(L_temp);
300 swActShift = add(2, swNormShift);
301 swDiv = divide_s(0x2000, swNormProd);
302 swRcOverE = mult_r(pswRc[i], swDiv);
303 }
304 /* Check stability */
305 /*---------------------*/
306 siUnstableFlt = siUnstableFlt | isSwLimit(swRcOverE);
307
308 /* Compute direct form filter coefficients corresponding to */
309 /* a direct form filter of order i-1 */
310 /*----------------------------------------------------------*/
311
312 for (j = 0; j <= i - 1; j++)
313 {
314 L_temp = L_mult(pswA[j], swDiv);
315 L_temp = L_msu(L_temp, pswA[i - j - 1], swRcOverE);
316 L_temp = L_shl(L_temp, swActShift);
317 pswTmp[j] = round(L_temp);
318 siUnstableFlt = siUnstableFlt | isSwLimit(pswTmp[j]);
319 }
320
321 /* Swap swA and swTmp buffers */
322 /*----------------------------*/
323
324 pswSwap = pswA;
325 pswA = pswTmp;
326 pswTmp = pswSwap;
327 }
328
329 /* Compute reflection coefficient Rc[0] */
330 /*--------------------------------------*/
331
332 pswRc[0] = shl(pswA[0], swAshift); /* write Rc[0] to output array */
333
334 /* Check the stability of 0-th reflection coefficient */
335 /*----------------------------------------------------*/
336
337 siUnstableFlt = siUnstableFlt | isSwLimit(pswRc[0]);
338
339 return (siUnstableFlt);
340 }
341 150
342 /*************************************************************************** 151 /***************************************************************************
343 * 152 *
344 * FUNCTION NAME: a_sst 153 * FUNCTION NAME: a_sst
345 * 154 *