1 /*
2 * Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
3 *
4 * Use of this source code is governed by a BSD-style license
5 * that can be found in the LICENSE file in the root of the source
6 * tree. An additional intellectual property rights grant can be found
7 * in the file PATENTS. All contributing project authors may
8 * be found in the AUTHORS file in the root of the source tree.
9 */
10
11 /*
12 * fft.c
13 *
14 * Fast Fourier Transform
15 *
16 */
17
18
19 #include "fft.h"
20
21 const WebRtc_Word16 kSortTabFft[240] = {
22 0, 60, 120, 180, 20, 80, 140, 200, 40, 100, 160, 220,
23 4, 64, 124, 184, 24, 84, 144, 204, 44, 104, 164, 224,
24 8, 68, 128, 188, 28, 88, 148, 208, 48, 108, 168, 228,
25 12, 72, 132, 192, 32, 92, 152, 212, 52, 112, 172, 232,
26 16, 76, 136, 196, 36, 96, 156, 216, 56, 116, 176, 236,
27 1, 61, 121, 181, 21, 81, 141, 201, 41, 101, 161, 221,
28 5, 65, 125, 185, 25, 85, 145, 205, 45, 105, 165, 225,
29 9, 69, 129, 189, 29, 89, 149, 209, 49, 109, 169, 229,
30 13, 73, 133, 193, 33, 93, 153, 213, 53, 113, 173, 233,
31 17, 77, 137, 197, 37, 97, 157, 217, 57, 117, 177, 237,
32 2, 62, 122, 182, 22, 82, 142, 202, 42, 102, 162, 222,
33 6, 66, 126, 186, 26, 86, 146, 206, 46, 106, 166, 226,
34 10, 70, 130, 190, 30, 90, 150, 210, 50, 110, 170, 230,
35 14, 74, 134, 194, 34, 94, 154, 214, 54, 114, 174, 234,
36 18, 78, 138, 198, 38, 98, 158, 218, 58, 118, 178, 238,
37 3, 63, 123, 183, 23, 83, 143, 203, 43, 103, 163, 223,
38 7, 67, 127, 187, 27, 87, 147, 207, 47, 107, 167, 227,
39 11, 71, 131, 191, 31, 91, 151, 211, 51, 111, 171, 231,
40 15, 75, 135, 195, 35, 95, 155, 215, 55, 115, 175, 235,
41 19, 79, 139, 199, 39, 99, 159, 219, 59, 119, 179, 239
42 };
43
44 /* Cosine table in Q14 */
45 const WebRtc_Word16 kCosTabFfftQ14[240] = {
46 16384, 16378, 16362, 16333, 16294, 16244, 16182, 16110, 16026, 15931, 15826, 15709,
47 15582, 15444, 15296, 15137, 14968, 14788, 14598, 14399, 14189, 13970, 13741, 13502,
48 13255, 12998, 12733, 12458, 12176, 11885, 11585, 11278, 10963, 10641, 10311, 9974,
49 9630, 9280, 8923, 8561, 8192, 7818, 7438, 7053, 6664, 6270, 5872, 5469,
50 5063, 4653, 4240, 3825, 3406, 2986, 2563, 2139, 1713, 1285, 857, 429,
51 0, -429, -857, -1285, -1713, -2139, -2563, -2986, -3406, -3825, -4240, -4653,
52 -5063, -5469, -5872, -6270, -6664, -7053, -7438, -7818, -8192, -8561, -8923, -9280,
53 -9630, -9974, -10311, -10641, -10963, -11278, -11585, -11885, -12176, -12458, -12733, -12998,
54 -13255, -13502, -13741, -13970, -14189, -14399, -14598, -14788, -14968, -15137, -15296, -15444,
55 -15582, -15709, -15826, -15931, -16026, -16110, -16182, -16244, -16294, -16333, -16362, -16378,
56 -16384, -16378, -16362, -16333, -16294, -16244, -16182, -16110, -16026, -15931, -15826, -15709,
57 -15582, -15444, -15296, -15137, -14968, -14788, -14598, -14399, -14189, -13970, -13741, -13502,
58 -13255, -12998, -12733, -12458, -12176, -11885, -11585, -11278, -10963, -10641, -10311, -9974,
59 -9630, -9280, -8923, -8561, -8192, -7818, -7438, -7053, -6664, -6270, -5872, -5469,
60 -5063, -4653, -4240, -3825, -3406, -2986, -2563, -2139, -1713, -1285, -857, -429,
61 0, 429, 857, 1285, 1713, 2139, 2563, 2986, 3406, 3825, 4240, 4653,
62 5063, 5469, 5872, 6270, 6664, 7053, 7438, 7818, 8192, 8561, 8923, 9280,
63 9630, 9974, 10311, 10641, 10963, 11278, 11585, 11885, 12176, 12458, 12733, 12998,
64 13255, 13502, 13741, 13970, 14189, 14399, 14598, 14788, 14968, 15137, 15296, 15444,
65 15582, 15709, 15826, 15931, 16026, 16110, 16182, 16244, 16294, 16333, 16362, 16378
66 };
67
68
69
70 /* Uses 16x16 mul, without rounding, which is faster. Uses WEBRTC_SPL_MUL_16_16_RSFT */
WebRtcIsacfix_FftRadix16Fastest(WebRtc_Word16 RexQx[],WebRtc_Word16 ImxQx[],WebRtc_Word16 iSign)71 WebRtc_Word16 WebRtcIsacfix_FftRadix16Fastest(WebRtc_Word16 RexQx[], WebRtc_Word16 ImxQx[], WebRtc_Word16 iSign) {
72
73 WebRtc_Word16 dd, ee, ff, gg, hh, ii;
74 WebRtc_Word16 k0, k1, k2, k3, k4, kk;
75 WebRtc_Word16 tmp116, tmp216;
76
77 WebRtc_Word16 ccc1Q14, ccc2Q14, ccc3Q14, sss1Q14, sss2Q14, sss3Q14;
78 WebRtc_Word16 sss60Q14, ccc72Q14, sss72Q14;
79 WebRtc_Word16 aaQx, ajQx, akQx, ajmQx, ajpQx, akmQx, akpQx;
80 WebRtc_Word16 bbQx, bjQx, bkQx, bjmQx, bjpQx, bkmQx, bkpQx;
81
82 WebRtc_Word16 ReDATAQx[240], ImDATAQx[240];
83
84 sss60Q14 = kCosTabFfftQ14[20];
85 ccc72Q14 = kCosTabFfftQ14[48];
86 sss72Q14 = kCosTabFfftQ14[12];
87
88 if (iSign < 0) {
89 sss72Q14 = -sss72Q14;
90 sss60Q14 = -sss60Q14;
91 }
92 /* Complexity is: 10 cycles */
93
94 /* compute fourier transform */
95
96 // transform for factor of 4
97 for (kk=0; kk<60; kk++) {
98 k0 = kk;
99 k1 = k0 + 60;
100 k2 = k1 + 60;
101 k3 = k2 + 60;
102
103 akpQx = RexQx[k0] + RexQx[k2];
104 akmQx = RexQx[k0] - RexQx[k2];
105 ajpQx = RexQx[k1] + RexQx[k3];
106 ajmQx = RexQx[k1] - RexQx[k3];
107 bkpQx = ImxQx[k0] + ImxQx[k2];
108 bkmQx = ImxQx[k0] - ImxQx[k2];
109 bjpQx = ImxQx[k1] + ImxQx[k3];
110 bjmQx = ImxQx[k1] - ImxQx[k3];
111
112 RexQx[k0] = akpQx + ajpQx;
113 ImxQx[k0] = bkpQx + bjpQx;
114 ajpQx = akpQx - ajpQx;
115 bjpQx = bkpQx - bjpQx;
116 if (iSign < 0) {
117 akpQx = akmQx + bjmQx;
118 bkpQx = bkmQx - ajmQx;
119 akmQx -= bjmQx;
120 bkmQx += ajmQx;
121 } else {
122 akpQx = akmQx - bjmQx;
123 bkpQx = bkmQx + ajmQx;
124 akmQx += bjmQx;
125 bkmQx -= ajmQx;
126 }
127
128 ccc1Q14 = kCosTabFfftQ14[kk];
129 ccc2Q14 = kCosTabFfftQ14[WEBRTC_SPL_MUL_16_16(2, kk)];
130 ccc3Q14 = kCosTabFfftQ14[WEBRTC_SPL_MUL_16_16(3, kk)];
131 sss1Q14 = kCosTabFfftQ14[kk+60];
132 sss2Q14 = kCosTabFfftQ14[WEBRTC_SPL_MUL_16_16(2, kk)+60];
133 sss3Q14 = kCosTabFfftQ14[WEBRTC_SPL_MUL_16_16(3, kk)+60];
134 if (iSign==1) {
135 sss1Q14 = -sss1Q14;
136 sss2Q14 = -sss2Q14;
137 sss3Q14 = -sss3Q14;
138 }
139
140 //Do several multiplications like Q14*Q16>>14 = Q16
141 // RexQ16[k1] = akpQ16 * ccc1Q14 - bkpQ16 * sss1Q14;
142 // RexQ16[k2] = ajpQ16 * ccc2Q14 - bjpQ16 * sss2Q14;
143 // RexQ16[k3] = akmQ16 * ccc3Q14 - bkmQ16 * sss3Q14;
144 // ImxQ16[k1] = akpQ16 * sss1Q14 + bkpQ16 * ccc1Q14;
145 // ImxQ16[k2] = ajpQ16 * sss2Q14 + bjpQ16 * ccc2Q14;
146 // ImxQ16[k3] = akmQ16 * sss3Q14 + bkmQ16 * ccc3Q14;
147
148 RexQx[k1] = (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(ccc1Q14, akpQx, 14) -
149 (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(sss1Q14, bkpQx, 14); // 6 non-mul + 2 mul cycles, i.e. 8 cycles (6+2*7=20 cycles if 16x32mul)
150 RexQx[k2] = (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(ccc2Q14, ajpQx, 14) -
151 (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(sss2Q14, bjpQx, 14);
152 RexQx[k3] = (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(ccc3Q14, akmQx, 14) -
153 (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(sss3Q14, bkmQx, 14);
154 ImxQx[k1] = (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(sss1Q14, akpQx, 14) +
155 (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(ccc1Q14, bkpQx, 14);
156 ImxQx[k2] = (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(sss2Q14, ajpQx, 14) +
157 (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(ccc2Q14, bjpQx, 14);
158 ImxQx[k3] = (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(sss3Q14, akmQx, 14) +
159 (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(ccc3Q14, bkmQx, 14);
160 //This mul segment needs 6*8 = 48 cycles for 16x16 muls, but 6*20 = 120 cycles for 16x32 muls
161
162
163 }
164 /* Complexity is: 51+48 = 99 cycles for 16x16 muls, but 51+120 = 171 cycles for 16x32 muls*/
165
166 // transform for factor of 3
167 kk=0;
168 k1=20;
169 k2=40;
170
171 for (hh=0; hh<4; hh++) {
172 for (ii=0; ii<20; ii++) {
173 akQx = RexQx[kk];
174 bkQx = ImxQx[kk];
175 ajQx = RexQx[k1] + RexQx[k2];
176 bjQx = ImxQx[k1] + ImxQx[k2];
177 RexQx[kk] = akQx + ajQx;
178 ImxQx[kk] = bkQx + bjQx;
179 tmp116 = WEBRTC_SPL_RSHIFT_W16(ajQx, 1);
180 tmp216 = WEBRTC_SPL_RSHIFT_W16(bjQx, 1);
181 akQx = akQx - tmp116;
182 bkQx = bkQx - tmp216;
183 tmp116 = RexQx[k1] - RexQx[k2];
184 tmp216 = ImxQx[k1] - ImxQx[k2];
185
186 ajQx = (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(sss60Q14, tmp116, 14); // Q14*Qx>>14 = Qx
187 bjQx = (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(sss60Q14, tmp216, 14); // Q14*Qx>>14 = Qx
188 RexQx[k1] = akQx - bjQx;
189 RexQx[k2] = akQx + bjQx;
190 ImxQx[k1] = bkQx + ajQx;
191 ImxQx[k2] = bkQx - ajQx;
192
193 kk++;
194 k1++;
195 k2++;
196 }
197 /* Complexity : (31+6)*20 = 740 cycles for 16x16 muls, but (31+18)*20 = 980 cycles for 16x32 muls*/
198 kk=kk+40;
199 k1=k1+40;
200 k2=k2+40;
201 }
202 /* Complexity : 4*(740+3) = 2972 cycles for 16x16 muls, but 4*(980+3) = 3932 cycles for 16x32 muls*/
203
204 /* multiply by rotation factor for odd factor 3 or 5 (not for 4)
205 Same code (duplicated) for both ii=2 and ii=3 */
206 kk = 1;
207 ee = 0;
208 ff = 0;
209
210 for (gg=0; gg<19; gg++) {
211 kk += 20;
212 ff = ff+4;
213 for (hh=0; hh<2; hh++) {
214 ee = ff + (WebRtc_Word16)WEBRTC_SPL_MUL_16_16(hh, ff);
215 dd = ee + 60;
216 ccc2Q14 = kCosTabFfftQ14[ee];
217 sss2Q14 = kCosTabFfftQ14[dd];
218 if (iSign==1) {
219 sss2Q14 = -sss2Q14;
220 }
221 for (ii=0; ii<4; ii++) {
222 akQx = RexQx[kk];
223 bkQx = ImxQx[kk];
224 RexQx[kk] = (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(ccc2Q14, akQx, 14) - // Q14*Qx>>14 = Qx
225 (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(sss2Q14, bkQx, 14);
226 ImxQx[kk] = (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(sss2Q14, akQx, 14) + // Q14*Qx>>14 = Qx
227 (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(ccc2Q14, bkQx, 14);
228
229
230 kk += 60;
231 }
232 kk = kk - 220;
233 }
234 // Complexity: 2*(13+5+4*13+2) = 144 for 16x16 muls, but 2*(13+5+4*33+2) = 304 cycles for 16x32 muls
235 kk = kk - 59;
236 }
237 // Complexity: 19*144 = 2736 for 16x16 muls, but 19*304 = 5776 cycles for 16x32 muls
238
239 // transform for factor of 5
240 kk = 0;
241 ccc2Q14 = kCosTabFfftQ14[96];
242 sss2Q14 = kCosTabFfftQ14[84];
243 if (iSign==1) {
244 sss2Q14 = -sss2Q14;
245 }
246
247 for (hh=0; hh<4; hh++) {
248 for (ii=0; ii<12; ii++) {
249 k1 = kk + 4;
250 k2 = k1 + 4;
251 k3 = k2 + 4;
252 k4 = k3 + 4;
253
254 akpQx = RexQx[k1] + RexQx[k4];
255 akmQx = RexQx[k1] - RexQx[k4];
256 bkpQx = ImxQx[k1] + ImxQx[k4];
257 bkmQx = ImxQx[k1] - ImxQx[k4];
258 ajpQx = RexQx[k2] + RexQx[k3];
259 ajmQx = RexQx[k2] - RexQx[k3];
260 bjpQx = ImxQx[k2] + ImxQx[k3];
261 bjmQx = ImxQx[k2] - ImxQx[k3];
262 aaQx = RexQx[kk];
263 bbQx = ImxQx[kk];
264 RexQx[kk] = aaQx + akpQx + ajpQx;
265 ImxQx[kk] = bbQx + bkpQx + bjpQx;
266
267 akQx = (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(ccc72Q14, akpQx, 14) +
268 (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(ccc2Q14, ajpQx, 14) + aaQx;
269 bkQx = (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(ccc72Q14, bkpQx, 14) +
270 (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(ccc2Q14, bjpQx, 14) + bbQx;
271 ajQx = (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(sss72Q14, akmQx, 14) +
272 (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(sss2Q14, ajmQx, 14);
273 bjQx = (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(sss72Q14, bkmQx, 14) +
274 (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(sss2Q14, bjmQx, 14);
275 // 32+4*8=64 or 32+4*20=112
276
277 RexQx[k1] = akQx - bjQx;
278 RexQx[k4] = akQx + bjQx;
279 ImxQx[k1] = bkQx + ajQx;
280 ImxQx[k4] = bkQx - ajQx;
281
282 akQx = (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(ccc2Q14, akpQx, 14) +
283 (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(ccc72Q14, ajpQx, 14) + aaQx;
284 bkQx = (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(ccc2Q14, bkpQx, 14) +
285 (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(ccc72Q14, bjpQx, 14) + bbQx;
286 ajQx = (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(sss2Q14, akmQx, 14) -
287 (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(sss72Q14, ajmQx, 14);
288 bjQx = (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(sss2Q14, bkmQx, 14) -
289 (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(sss72Q14, bjmQx, 14);
290 // 8+4*8=40 or 8+4*20=88
291
292 RexQx[k2] = akQx - bjQx;
293 RexQx[k3] = akQx + bjQx;
294 ImxQx[k2] = bkQx + ajQx;
295 ImxQx[k3] = bkQx - ajQx;
296
297 kk = k4 + 4;
298 }
299 // Complexity: 12*(64+40+10) = 1368 for 16x16 muls, but 12*(112+88+10) = 2520 cycles for 16x32 muls
300 kk -= 239;
301 }
302 // Complexity: 4*1368 = 5472 for 16x16 muls, but 4*2520 = 10080 cycles for 16x32 muls
303
304 /* multiply by rotation factor for odd factor 3 or 5 (not for 4)
305 Same code (duplicated) for both ii=2 and ii=3 */
306 kk = 1;
307 ee=0;
308
309 for (gg=0; gg<3; gg++) {
310 kk += 4;
311 dd = 12 + (WebRtc_Word16)WEBRTC_SPL_MUL_16_16(12, gg);
312 ff = 0;
313 for (hh=0; hh<4; hh++) {
314 ff = ff+dd;
315 ee = ff+60;
316 for (ii=0; ii<12; ii++) {
317 akQx = RexQx[kk];
318 bkQx = ImxQx[kk];
319
320 ccc2Q14 = kCosTabFfftQ14[ff];
321 sss2Q14 = kCosTabFfftQ14[ee];
322
323 if (iSign==1) {
324 sss2Q14 = -sss2Q14;
325 }
326
327 RexQx[kk] = (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(ccc2Q14, akQx, 14) -
328 (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(sss2Q14, bkQx, 14);
329 ImxQx[kk] = (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(sss2Q14, akQx, 14) +
330 (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(ccc2Q14, bkQx, 14);
331
332 kk += 20;
333 }
334 kk = kk - 236;
335 // Complexity: 12*(12+12) = 288 for 16x16 muls, but 12*(12+32) = 528 cycles for 16x32 muls
336 }
337 kk = kk - 19;
338 // Complexity: 4*288+6 for 16x16 muls, but 4*528+6 cycles for 16x32 muls
339 }
340 // Complexity: 3*4*288+6 = 3462 for 16x16 muls, but 3*4*528+6 = 6342 cycles for 16x32 muls
341
342
343 // last transform for factor of 4 */
344 for (kk=0; kk<240; kk=kk+4) {
345 k1 = kk + 1;
346 k2 = k1 + 1;
347 k3 = k2 + 1;
348
349 akpQx = RexQx[kk] + RexQx[k2];
350 akmQx = RexQx[kk] - RexQx[k2];
351 ajpQx = RexQx[k1] + RexQx[k3];
352 ajmQx = RexQx[k1] - RexQx[k3];
353 bkpQx = ImxQx[kk] + ImxQx[k2];
354 bkmQx = ImxQx[kk] - ImxQx[k2];
355 bjpQx = ImxQx[k1] + ImxQx[k3];
356 bjmQx = ImxQx[k1] - ImxQx[k3];
357 RexQx[kk] = akpQx + ajpQx;
358 ImxQx[kk] = bkpQx + bjpQx;
359 ajpQx = akpQx - ajpQx;
360 bjpQx = bkpQx - bjpQx;
361 if (iSign < 0) {
362 akpQx = akmQx + bjmQx;
363 bkpQx = bkmQx - ajmQx;
364 akmQx -= bjmQx;
365 bkmQx += ajmQx;
366 } else {
367 akpQx = akmQx - bjmQx;
368 bkpQx = bkmQx + ajmQx;
369 akmQx += bjmQx;
370 bkmQx -= ajmQx;
371 }
372 RexQx[k1] = akpQx;
373 RexQx[k2] = ajpQx;
374 RexQx[k3] = akmQx;
375 ImxQx[k1] = bkpQx;
376 ImxQx[k2] = bjpQx;
377 ImxQx[k3] = bkmQx;
378 }
379 // Complexity: 60*45 = 2700 for 16x16 muls, but 60*45 = 2700 cycles for 16x32 muls
380
381 /* permute the results to normal order */
382 for (ii=0; ii<240; ii++) {
383 ReDATAQx[ii]=RexQx[ii];
384 ImDATAQx[ii]=ImxQx[ii];
385 }
386 // Complexity: 240*2=480 cycles
387
388 for (ii=0; ii<240; ii++) {
389 RexQx[ii]=ReDATAQx[kSortTabFft[ii]];
390 ImxQx[ii]=ImDATAQx[kSortTabFft[ii]];
391 }
392 // Complexity: 240*2*2=960 cycles
393
394 // Total complexity:
395 // 16x16 16x32
396 // Complexity: 10 10
397 // Complexity: 99 171
398 // Complexity: 2972 3932
399 // Complexity: 2736 5776
400 // Complexity: 5472 10080
401 // Complexity: 3462 6342
402 // Complexity: 2700 2700
403 // Complexity: 480 480
404 // Complexity: 960 960
405 // =======================
406 // 18891 30451
407 //
408 // If this FFT is called 2 time each frame, i.e. 67 times per second, it will correspond to
409 // a C54 complexity of 67*18891/1000000 = 1.27 MIPS with 16x16-muls, and 67*30451/1000000 =
410 // = 2.04 MIPS with 16x32-muls. Note that this routine somtimes is called 6 times during the
411 // encoding of a frame, i.e. the max complexity would be 7/2*1.27 = 4.4 MIPS for the 16x16 mul case.
412
413
414 return 0;
415 }
416