ffmpeg / libavcodec / mpegaudioenc.c @ 755bfeab
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/*


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* The simplest mpeg audio layer 2 encoder

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* Copyright (c) 2000, 2001 Fabrice Bellard.

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*

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* This file is part of FFmpeg.

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*

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* FFmpeg is free software; you can redistribute it and/or

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* modify it under the terms of the GNU Lesser General Public

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* License as published by the Free Software Foundation; either

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* version 2.1 of the License, or (at your option) any later version.

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*

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* FFmpeg is distributed in the hope that it will be useful,

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* but WITHOUT ANY WARRANTY; without even the implied warranty of

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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU

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* Lesser General Public License for more details.

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*

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* You should have received a copy of the GNU Lesser General Public

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* License along with FFmpeg; if not, write to the Free Software

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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 021101301 USA

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*/

21  
22 
/**

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* @file mpegaudio.c

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* The simplest mpeg audio layer 2 encoder.

25 
*/

26  
27 
#include "avcodec.h" 
28 
#include "bitstream.h" 
29 
#include "mpegaudio.h" 
30  
31 
/* currently, cannot change these constants (need to modify

32 
quantization stage) */

33 
#define MUL(a,b) (((int64_t)(a) * (int64_t)(b)) >> FRAC_BITS)

34 
#define FIX(a) ((int)((a) * (1 << FRAC_BITS))) 
35  
36 
#define SAMPLES_BUF_SIZE 4096 
37  
38 
typedef struct MpegAudioContext { 
39 
PutBitContext pb; 
40 
int nb_channels;

41 
int freq, bit_rate;

42 
int lsf; /* 1 if mpeg2 low bitrate selected */ 
43 
int bitrate_index; /* bit rate */ 
44 
int freq_index;

45 
int frame_size; /* frame size, in bits, without padding */ 
46 
int64_t nb_samples; /* total number of samples encoded */

47 
/* padding computation */

48 
int frame_frac, frame_frac_incr, do_padding;

49 
short samples_buf[MPA_MAX_CHANNELS][SAMPLES_BUF_SIZE]; /* buffer for filter */ 
50 
int samples_offset[MPA_MAX_CHANNELS]; /* offset in samples_buf */ 
51 
int sb_samples[MPA_MAX_CHANNELS][3][12][SBLIMIT]; 
52 
unsigned char scale_factors[MPA_MAX_CHANNELS][SBLIMIT][3]; /* scale factors */ 
53 
/* code to group 3 scale factors */

54 
unsigned char scale_code[MPA_MAX_CHANNELS][SBLIMIT]; 
55 
int sblimit; /* number of used subbands */ 
56 
const unsigned char *alloc_table; 
57 
} MpegAudioContext; 
58  
59 
/* define it to use floats in quantization (I don't like floats !) */

60 
//#define USE_FLOATS

61  
62 
#include "mpegaudiodata.h" 
63 
#include "mpegaudiotab.h" 
64  
65 
static int MPA_encode_init(AVCodecContext *avctx) 
66 
{ 
67 
MpegAudioContext *s = avctx>priv_data; 
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int freq = avctx>sample_rate;

69 
int bitrate = avctx>bit_rate;

70 
int channels = avctx>channels;

71 
int i, v, table;

72 
float a;

73  
74 
if (channels <= 0  channels > 2){ 
75 
av_log(avctx, AV_LOG_ERROR, "encoding %d channel(s) is not allowed in mp2\n", channels);

76 
return 1; 
77 
} 
78 
bitrate = bitrate / 1000;

79 
s>nb_channels = channels; 
80 
s>freq = freq; 
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s>bit_rate = bitrate * 1000;

82 
avctx>frame_size = MPA_FRAME_SIZE; 
83  
84 
/* encoding freq */

85 
s>lsf = 0;

86 
for(i=0;i<3;i++) { 
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if (ff_mpa_freq_tab[i] == freq)

88 
break;

89 
if ((ff_mpa_freq_tab[i] / 2) == freq) { 
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s>lsf = 1;

91 
break;

92 
} 
93 
} 
94 
if (i == 3){ 
95 
av_log(avctx, AV_LOG_ERROR, "Sampling rate %d is not allowed in mp2\n", freq);

96 
return 1; 
97 
} 
98 
s>freq_index = i; 
99  
100 
/* encoding bitrate & frequency */

101 
for(i=0;i<15;i++) { 
102 
if (ff_mpa_bitrate_tab[s>lsf][1][i] == bitrate) 
103 
break;

104 
} 
105 
if (i == 15){ 
106 
av_log(avctx, AV_LOG_ERROR, "bitrate %d is not allowed in mp2\n", bitrate);

107 
return 1; 
108 
} 
109 
s>bitrate_index = i; 
110  
111 
/* compute total header size & pad bit */

112  
113 
a = (float)(bitrate * 1000 * MPA_FRAME_SIZE) / (freq * 8.0); 
114 
s>frame_size = ((int)a) * 8; 
115  
116 
/* frame fractional size to compute padding */

117 
s>frame_frac = 0;

118 
s>frame_frac_incr = (int)((a  floor(a)) * 65536.0); 
119  
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/* select the right allocation table */

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table = ff_mpa_l2_select_table(bitrate, s>nb_channels, freq, s>lsf); 
122  
123 
/* number of used subbands */

124 
s>sblimit = ff_mpa_sblimit_table[table]; 
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s>alloc_table = ff_mpa_alloc_tables[table]; 
126  
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#ifdef DEBUG

128 
av_log(avctx, AV_LOG_DEBUG, "%d kb/s, %d Hz, frame_size=%d bits, table=%d, padincr=%x\n",

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bitrate, freq, s>frame_size, table, s>frame_frac_incr); 
130 
#endif

131  
132 
for(i=0;i<s>nb_channels;i++) 
133 
s>samples_offset[i] = 0;

134  
135 
for(i=0;i<257;i++) { 
136 
int v;

137 
v = ff_mpa_enwindow[i]; 
138 
#if WFRAC_BITS != 16 
139 
v = (v + (1 << (16  WFRAC_BITS  1))) >> (16  WFRAC_BITS); 
140 
#endif

141 
filter_bank[i] = v; 
142 
if ((i & 63) != 0) 
143 
v = v; 
144 
if (i != 0) 
145 
filter_bank[512  i] = v;

146 
} 
147  
148 
for(i=0;i<64;i++) { 
149 
v = (int)(pow(2.0, (3  i) / 3.0) * (1 << 20)); 
150 
if (v <= 0) 
151 
v = 1;

152 
scale_factor_table[i] = v; 
153 
#ifdef USE_FLOATS

154 
scale_factor_inv_table[i] = pow(2.0, (3  i) / 3.0) / (float)(1 << 20); 
155 
#else

156 
#define P 15 
157 
scale_factor_shift[i] = 21  P  (i / 3); 
158 
scale_factor_mult[i] = (1 << P) * pow(2.0, (i % 3) / 3.0); 
159 
#endif

160 
} 
161 
for(i=0;i<128;i++) { 
162 
v = i  64;

163 
if (v <= 3) 
164 
v = 0;

165 
else if (v < 0) 
166 
v = 1;

167 
else if (v == 0) 
168 
v = 2;

169 
else if (v < 3) 
170 
v = 3;

171 
else

172 
v = 4;

173 
scale_diff_table[i] = v; 
174 
} 
175  
176 
for(i=0;i<17;i++) { 
177 
v = ff_mpa_quant_bits[i]; 
178 
if (v < 0) 
179 
v = v; 
180 
else

181 
v = v * 3;

182 
total_quant_bits[i] = 12 * v;

183 
} 
184  
185 
avctx>coded_frame= avcodec_alloc_frame(); 
186 
avctx>coded_frame>key_frame= 1;

187  
188 
return 0; 
189 
} 
190  
191 
/* 32 point floating point IDCT without 1/sqrt(2) coef zero scaling */

192 
static void idct32(int *out, int *tab) 
193 
{ 
194 
int i, j;

195 
int *t, *t1, xr;

196 
const int *xp = costab32; 
197  
198 
for(j=31;j>=3;j=2) tab[j] += tab[j  2]; 
199  
200 
t = tab + 30;

201 
t1 = tab + 2;

202 
do {

203 
t[0] += t[4]; 
204 
t[1] += t[1  4]; 
205 
t = 4;

206 
} while (t != t1);

207  
208 
t = tab + 28;

209 
t1 = tab + 4;

210 
do {

211 
t[0] += t[8]; 
212 
t[1] += t[18]; 
213 
t[2] += t[28]; 
214 
t[3] += t[38]; 
215 
t = 8;

216 
} while (t != t1);

217  
218 
t = tab; 
219 
t1 = tab + 32;

220 
do {

221 
t[ 3] = t[ 3]; 
222 
t[ 6] = t[ 6]; 
223  
224 
t[11] = t[11]; 
225 
t[12] = t[12]; 
226 
t[13] = t[13]; 
227 
t[15] = t[15]; 
228 
t += 16;

229 
} while (t != t1);

230  
231  
232 
t = tab; 
233 
t1 = tab + 8;

234 
do {

235 
int x1, x2, x3, x4;

236  
237 
x3 = MUL(t[16], FIX(SQRT2*0.5)); 
238 
x4 = t[0]  x3;

239 
x3 = t[0] + x3;

240  
241 
x2 = MUL((t[24] + t[8]), FIX(SQRT2*0.5)); 
242 
x1 = MUL((t[8]  x2), xp[0]); 
243 
x2 = MUL((t[8] + x2), xp[1]); 
244  
245 
t[ 0] = x3 + x1;

246 
t[ 8] = x4  x2;

247 
t[16] = x4 + x2;

248 
t[24] = x3  x1;

249 
t++; 
250 
} while (t != t1);

251  
252 
xp += 2;

253 
t = tab; 
254 
t1 = tab + 4;

255 
do {

256 
xr = MUL(t[28],xp[0]); 
257 
t[28] = (t[0]  xr); 
258 
t[0] = (t[0] + xr); 
259  
260 
xr = MUL(t[4],xp[1]); 
261 
t[ 4] = (t[24]  xr); 
262 
t[24] = (t[24] + xr); 
263  
264 
xr = MUL(t[20],xp[2]); 
265 
t[20] = (t[8]  xr); 
266 
t[ 8] = (t[8] + xr); 
267  
268 
xr = MUL(t[12],xp[3]); 
269 
t[12] = (t[16]  xr); 
270 
t[16] = (t[16] + xr); 
271 
t++; 
272 
} while (t != t1);

273 
xp += 4;

274  
275 
for (i = 0; i < 4; i++) { 
276 
xr = MUL(tab[30i*4],xp[0]); 
277 
tab[30i*4] = (tab[i*4]  xr); 
278 
tab[ i*4] = (tab[i*4] + xr); 
279  
280 
xr = MUL(tab[ 2+i*4],xp[1]); 
281 
tab[ 2+i*4] = (tab[28i*4]  xr); 
282 
tab[28i*4] = (tab[28i*4] + xr); 
283  
284 
xr = MUL(tab[31i*4],xp[0]); 
285 
tab[31i*4] = (tab[1+i*4]  xr); 
286 
tab[ 1+i*4] = (tab[1+i*4] + xr); 
287  
288 
xr = MUL(tab[ 3+i*4],xp[1]); 
289 
tab[ 3+i*4] = (tab[29i*4]  xr); 
290 
tab[29i*4] = (tab[29i*4] + xr); 
291  
292 
xp += 2;

293 
} 
294  
295 
t = tab + 30;

296 
t1 = tab + 1;

297 
do {

298 
xr = MUL(t1[0], *xp);

299 
t1[0] = (t[0]  xr); 
300 
t[0] = (t[0] + xr); 
301 
t = 2;

302 
t1 += 2;

303 
xp++; 
304 
} while (t >= tab);

305  
306 
for(i=0;i<32;i++) { 
307 
out[i] = tab[bitinv32[i]]; 
308 
} 
309 
} 
310  
311 
#define WSHIFT (WFRAC_BITS + 15  FRAC_BITS) 
312  
313 
static void filter(MpegAudioContext *s, int ch, short *samples, int incr) 
314 
{ 
315 
short *p, *q;

316 
int sum, offset, i, j;

317 
int tmp[64]; 
318 
int tmp1[32]; 
319 
int *out;

320  
321 
// print_pow1(samples, 1152);

322  
323 
offset = s>samples_offset[ch]; 
324 
out = &s>sb_samples[ch][0][0][0]; 
325 
for(j=0;j<36;j++) { 
326 
/* 32 samples at once */

327 
for(i=0;i<32;i++) { 
328 
s>samples_buf[ch][offset + (31  i)] = samples[0]; 
329 
samples += incr; 
330 
} 
331  
332 
/* filter */

333 
p = s>samples_buf[ch] + offset; 
334 
q = filter_bank; 
335 
/* maxsum = 23169 */

336 
for(i=0;i<64;i++) { 
337 
sum = p[0*64] * q[0*64]; 
338 
sum += p[1*64] * q[1*64]; 
339 
sum += p[2*64] * q[2*64]; 
340 
sum += p[3*64] * q[3*64]; 
341 
sum += p[4*64] * q[4*64]; 
342 
sum += p[5*64] * q[5*64]; 
343 
sum += p[6*64] * q[6*64]; 
344 
sum += p[7*64] * q[7*64]; 
345 
tmp[i] = sum; 
346 
p++; 
347 
q++; 
348 
} 
349 
tmp1[0] = tmp[16] >> WSHIFT; 
350 
for( i=1; i<=16; i++ ) tmp1[i] = (tmp[i+16]+tmp[16i]) >> WSHIFT; 
351 
for( i=17; i<=31; i++ ) tmp1[i] = (tmp[i+16]tmp[80i]) >> WSHIFT; 
352  
353 
idct32(out, tmp1); 
354  
355 
/* advance of 32 samples */

356 
offset = 32;

357 
out += 32;

358 
/* handle the wrap around */

359 
if (offset < 0) { 
360 
memmove(s>samples_buf[ch] + SAMPLES_BUF_SIZE  (512  32), 
361 
s>samples_buf[ch], (512  32) * 2); 
362 
offset = SAMPLES_BUF_SIZE  512;

363 
} 
364 
} 
365 
s>samples_offset[ch] = offset; 
366  
367 
// print_pow(s>sb_samples, 1152);

368 
} 
369  
370 
static void compute_scale_factors(unsigned char scale_code[SBLIMIT], 
371 
unsigned char scale_factors[SBLIMIT][3], 
372 
int sb_samples[3][12][SBLIMIT], 
373 
int sblimit)

374 
{ 
375 
int *p, vmax, v, n, i, j, k, code;

376 
int index, d1, d2;

377 
unsigned char *sf = &scale_factors[0][0]; 
378  
379 
for(j=0;j<sblimit;j++) { 
380 
for(i=0;i<3;i++) { 
381 
/* find the max absolute value */

382 
p = &sb_samples[i][0][j];

383 
vmax = abs(*p); 
384 
for(k=1;k<12;k++) { 
385 
p += SBLIMIT; 
386 
v = abs(*p); 
387 
if (v > vmax)

388 
vmax = v; 
389 
} 
390 
/* compute the scale factor index using log 2 computations */

391 
if (vmax > 0) { 
392 
n = av_log2(vmax); 
393 
/* n is the position of the MSB of vmax. now

394 
use at most 2 compares to find the index */

395 
index = (21  n) * 3  3; 
396 
if (index >= 0) { 
397 
while (vmax <= scale_factor_table[index+1]) 
398 
index++; 
399 
} else {

400 
index = 0; /* very unlikely case of overflow */ 
401 
} 
402 
} else {

403 
index = 62; /* value 63 is not allowed */ 
404 
} 
405  
406 
#if 0

407 
printf("%2d:%d in=%x %x %d\n",

408 
j, i, vmax, scale_factor_table[index], index);

409 
#endif

410 
/* store the scale factor */

411 
assert(index >=0 && index <= 63); 
412 
sf[i] = index; 
413 
} 
414  
415 
/* compute the transmission factor : look if the scale factors

416 
are close enough to each other */

417 
d1 = scale_diff_table[sf[0]  sf[1] + 64]; 
418 
d2 = scale_diff_table[sf[1]  sf[2] + 64]; 
419  
420 
/* handle the 25 cases */

421 
switch(d1 * 5 + d2) { 
422 
case 0*5+0: 
423 
case 0*5+4: 
424 
case 3*5+4: 
425 
case 4*5+0: 
426 
case 4*5+4: 
427 
code = 0;

428 
break;

429 
case 0*5+1: 
430 
case 0*5+2: 
431 
case 4*5+1: 
432 
case 4*5+2: 
433 
code = 3;

434 
sf[2] = sf[1]; 
435 
break;

436 
case 0*5+3: 
437 
case 4*5+3: 
438 
code = 3;

439 
sf[1] = sf[2]; 
440 
break;

441 
case 1*5+0: 
442 
case 1*5+4: 
443 
case 2*5+4: 
444 
code = 1;

445 
sf[1] = sf[0]; 
446 
break;

447 
case 1*5+1: 
448 
case 1*5+2: 
449 
case 2*5+0: 
450 
case 2*5+1: 
451 
case 2*5+2: 
452 
code = 2;

453 
sf[1] = sf[2] = sf[0]; 
454 
break;

455 
case 2*5+3: 
456 
case 3*5+3: 
457 
code = 2;

458 
sf[0] = sf[1] = sf[2]; 
459 
break;

460 
case 3*5+0: 
461 
case 3*5+1: 
462 
case 3*5+2: 
463 
code = 2;

464 
sf[0] = sf[2] = sf[1]; 
465 
break;

466 
case 1*5+3: 
467 
code = 2;

468 
if (sf[0] > sf[2]) 
469 
sf[0] = sf[2]; 
470 
sf[1] = sf[2] = sf[0]; 
471 
break;

472 
default:

473 
assert(0); //cannot happen 
474 
code = 0; /* kill warning */ 
475 
} 
476  
477 
#if 0

478 
printf("%d: %2d %2d %2d %d %d > %d\n", j,

479 
sf[0], sf[1], sf[2], d1, d2, code);

480 
#endif

481 
scale_code[j] = code; 
482 
sf += 3;

483 
} 
484 
} 
485  
486 
/* The most important function : psycho acoustic module. In this

487 
encoder there is basically none, so this is the worst you can do,

488 
but also this is the simpler. */

489 
static void psycho_acoustic_model(MpegAudioContext *s, short smr[SBLIMIT]) 
490 
{ 
491 
int i;

492  
493 
for(i=0;i<s>sblimit;i++) { 
494 
smr[i] = (int)(fixed_smr[i] * 10); 
495 
} 
496 
} 
497  
498  
499 
#define SB_NOTALLOCATED 0 
500 
#define SB_ALLOCATED 1 
501 
#define SB_NOMORE 2 
502  
503 
/* Try to maximize the smr while using a number of bits inferior to

504 
the frame size. I tried to make the code simpler, faster and

505 
smaller than other encoders :) */

506 
static void compute_bit_allocation(MpegAudioContext *s, 
507 
short smr1[MPA_MAX_CHANNELS][SBLIMIT],

508 
unsigned char bit_alloc[MPA_MAX_CHANNELS][SBLIMIT], 
509 
int *padding)

510 
{ 
511 
int i, ch, b, max_smr, max_ch, max_sb, current_frame_size, max_frame_size;

512 
int incr;

513 
short smr[MPA_MAX_CHANNELS][SBLIMIT];

514 
unsigned char subband_status[MPA_MAX_CHANNELS][SBLIMIT]; 
515 
const unsigned char *alloc; 
516  
517 
memcpy(smr, smr1, s>nb_channels * sizeof(short) * SBLIMIT); 
518 
memset(subband_status, SB_NOTALLOCATED, s>nb_channels * SBLIMIT); 
519 
memset(bit_alloc, 0, s>nb_channels * SBLIMIT);

520  
521 
/* compute frame size and padding */

522 
max_frame_size = s>frame_size; 
523 
s>frame_frac += s>frame_frac_incr; 
524 
if (s>frame_frac >= 65536) { 
525 
s>frame_frac = 65536;

526 
s>do_padding = 1;

527 
max_frame_size += 8;

528 
} else {

529 
s>do_padding = 0;

530 
} 
531  
532 
/* compute the header + bit alloc size */

533 
current_frame_size = 32;

534 
alloc = s>alloc_table; 
535 
for(i=0;i<s>sblimit;i++) { 
536 
incr = alloc[0];

537 
current_frame_size += incr * s>nb_channels; 
538 
alloc += 1 << incr;

539 
} 
540 
for(;;) {

541 
/* look for the subband with the largest signal to mask ratio */

542 
max_sb = 1;

543 
max_ch = 1;

544 
max_smr = 0x80000000;

545 
for(ch=0;ch<s>nb_channels;ch++) { 
546 
for(i=0;i<s>sblimit;i++) { 
547 
if (smr[ch][i] > max_smr && subband_status[ch][i] != SB_NOMORE) {

548 
max_smr = smr[ch][i]; 
549 
max_sb = i; 
550 
max_ch = ch; 
551 
} 
552 
} 
553 
} 
554 
#if 0

555 
printf("current=%d max=%d max_sb=%d alloc=%d\n",

556 
current_frame_size, max_frame_size, max_sb,

557 
bit_alloc[max_sb]);

558 
#endif

559 
if (max_sb < 0) 
560 
break;

561  
562 
/* find alloc table entry (XXX: not optimal, should use

563 
pointer table) */

564 
alloc = s>alloc_table; 
565 
for(i=0;i<max_sb;i++) { 
566 
alloc += 1 << alloc[0]; 
567 
} 
568  
569 
if (subband_status[max_ch][max_sb] == SB_NOTALLOCATED) {

570 
/* nothing was coded for this band: add the necessary bits */

571 
incr = 2 + nb_scale_factors[s>scale_code[max_ch][max_sb]] * 6; 
572 
incr += total_quant_bits[alloc[1]];

573 
} else {

574 
/* increments bit allocation */

575 
b = bit_alloc[max_ch][max_sb]; 
576 
incr = total_quant_bits[alloc[b + 1]] 

577 
total_quant_bits[alloc[b]]; 
578 
} 
579  
580 
if (current_frame_size + incr <= max_frame_size) {

581 
/* can increase size */

582 
b = ++bit_alloc[max_ch][max_sb]; 
583 
current_frame_size += incr; 
584 
/* decrease smr by the resolution we added */

585 
smr[max_ch][max_sb] = smr1[max_ch][max_sb]  quant_snr[alloc[b]]; 
586 
/* max allocation size reached ? */

587 
if (b == ((1 << alloc[0])  1)) 
588 
subband_status[max_ch][max_sb] = SB_NOMORE; 
589 
else

590 
subband_status[max_ch][max_sb] = SB_ALLOCATED; 
591 
} else {

592 
/* cannot increase the size of this subband */

593 
subband_status[max_ch][max_sb] = SB_NOMORE; 
594 
} 
595 
} 
596 
*padding = max_frame_size  current_frame_size; 
597 
assert(*padding >= 0);

598  
599 
#if 0

600 
for(i=0;i<s>sblimit;i++) {

601 
printf("%d ", bit_alloc[i]);

602 
}

603 
printf("\n");

604 
#endif

605 
} 
606  
607 
/*

608 
* Output the mpeg audio layer 2 frame. Note how the code is small

609 
* compared to other encoders :)

610 
*/

611 
static void encode_frame(MpegAudioContext *s, 
612 
unsigned char bit_alloc[MPA_MAX_CHANNELS][SBLIMIT], 
613 
int padding)

614 
{ 
615 
int i, j, k, l, bit_alloc_bits, b, ch;

616 
unsigned char *sf; 
617 
int q[3]; 
618 
PutBitContext *p = &s>pb; 
619  
620 
/* header */

621  
622 
put_bits(p, 12, 0xfff); 
623 
put_bits(p, 1, 1  s>lsf); /* 1 = mpeg1 ID, 0 = mpeg2 lsf ID */ 
624 
put_bits(p, 2, 42); /* layer 2 */ 
625 
put_bits(p, 1, 1); /* no error protection */ 
626 
put_bits(p, 4, s>bitrate_index);

627 
put_bits(p, 2, s>freq_index);

628 
put_bits(p, 1, s>do_padding); /* use padding */ 
629 
put_bits(p, 1, 0); /* private_bit */ 
630 
put_bits(p, 2, s>nb_channels == 2 ? MPA_STEREO : MPA_MONO); 
631 
put_bits(p, 2, 0); /* mode_ext */ 
632 
put_bits(p, 1, 0); /* no copyright */ 
633 
put_bits(p, 1, 1); /* original */ 
634 
put_bits(p, 2, 0); /* no emphasis */ 
635  
636 
/* bit allocation */

637 
j = 0;

638 
for(i=0;i<s>sblimit;i++) { 
639 
bit_alloc_bits = s>alloc_table[j]; 
640 
for(ch=0;ch<s>nb_channels;ch++) { 
641 
put_bits(p, bit_alloc_bits, bit_alloc[ch][i]); 
642 
} 
643 
j += 1 << bit_alloc_bits;

644 
} 
645  
646 
/* scale codes */

647 
for(i=0;i<s>sblimit;i++) { 
648 
for(ch=0;ch<s>nb_channels;ch++) { 
649 
if (bit_alloc[ch][i])

650 
put_bits(p, 2, s>scale_code[ch][i]);

651 
} 
652 
} 
653  
654 
/* scale factors */

655 
for(i=0;i<s>sblimit;i++) { 
656 
for(ch=0;ch<s>nb_channels;ch++) { 
657 
if (bit_alloc[ch][i]) {

658 
sf = &s>scale_factors[ch][i][0];

659 
switch(s>scale_code[ch][i]) {

660 
case 0: 
661 
put_bits(p, 6, sf[0]); 
662 
put_bits(p, 6, sf[1]); 
663 
put_bits(p, 6, sf[2]); 
664 
break;

665 
case 3: 
666 
case 1: 
667 
put_bits(p, 6, sf[0]); 
668 
put_bits(p, 6, sf[2]); 
669 
break;

670 
case 2: 
671 
put_bits(p, 6, sf[0]); 
672 
break;

673 
} 
674 
} 
675 
} 
676 
} 
677  
678 
/* quantization & write sub band samples */

679  
680 
for(k=0;k<3;k++) { 
681 
for(l=0;l<12;l+=3) { 
682 
j = 0;

683 
for(i=0;i<s>sblimit;i++) { 
684 
bit_alloc_bits = s>alloc_table[j]; 
685 
for(ch=0;ch<s>nb_channels;ch++) { 
686 
b = bit_alloc[ch][i]; 
687 
if (b) {

688 
int qindex, steps, m, sample, bits;

689 
/* we encode 3 sub band samples of the same sub band at a time */

690 
qindex = s>alloc_table[j+b]; 
691 
steps = ff_mpa_quant_steps[qindex]; 
692 
for(m=0;m<3;m++) { 
693 
sample = s>sb_samples[ch][k][l + m][i]; 
694 
/* divide by scale factor */

695 
#ifdef USE_FLOATS

696 
{ 
697 
float a;

698 
a = (float)sample * scale_factor_inv_table[s>scale_factors[ch][i][k]];

699 
q[m] = (int)((a + 1.0) * steps * 0.5); 
700 
} 
701 
#else

702 
{ 
703 
int q1, e, shift, mult;

704 
e = s>scale_factors[ch][i][k]; 
705 
shift = scale_factor_shift[e]; 
706 
mult = scale_factor_mult[e]; 
707  
708 
/* normalize to P bits */

709 
if (shift < 0) 
710 
q1 = sample << (shift); 
711 
else

712 
q1 = sample >> shift; 
713 
q1 = (q1 * mult) >> P; 
714 
q[m] = ((q1 + (1 << P)) * steps) >> (P + 1); 
715 
} 
716 
#endif

717 
if (q[m] >= steps)

718 
q[m] = steps  1;

719 
assert(q[m] >= 0 && q[m] < steps);

720 
} 
721 
bits = ff_mpa_quant_bits[qindex]; 
722 
if (bits < 0) { 
723 
/* group the 3 values to save bits */

724 
put_bits(p, bits, 
725 
q[0] + steps * (q[1] + steps * q[2])); 
726 
#if 0

727 
printf("%d: gr1 %d\n",

728 
i, q[0] + steps * (q[1] + steps * q[2]));

729 
#endif

730 
} else {

731 
#if 0

732 
printf("%d: gr3 %d %d %d\n",

733 
i, q[0], q[1], q[2]);

734 
#endif

735 
put_bits(p, bits, q[0]);

736 
put_bits(p, bits, q[1]);

737 
put_bits(p, bits, q[2]);

738 
} 
739 
} 
740 
} 
741 
/* next subband in alloc table */

742 
j += 1 << bit_alloc_bits;

743 
} 
744 
} 
745 
} 
746  
747 
/* padding */

748 
for(i=0;i<padding;i++) 
749 
put_bits(p, 1, 0); 
750  
751 
/* flush */

752 
flush_put_bits(p); 
753 
} 
754  
755 
static int MPA_encode_frame(AVCodecContext *avctx, 
756 
unsigned char *frame, int buf_size, void *data) 
757 
{ 
758 
MpegAudioContext *s = avctx>priv_data; 
759 
short *samples = data;

760 
short smr[MPA_MAX_CHANNELS][SBLIMIT];

761 
unsigned char bit_alloc[MPA_MAX_CHANNELS][SBLIMIT]; 
762 
int padding, i;

763  
764 
for(i=0;i<s>nb_channels;i++) { 
765 
filter(s, i, samples + i, s>nb_channels); 
766 
} 
767  
768 
for(i=0;i<s>nb_channels;i++) { 
769 
compute_scale_factors(s>scale_code[i], s>scale_factors[i], 
770 
s>sb_samples[i], s>sblimit); 
771 
} 
772 
for(i=0;i<s>nb_channels;i++) { 
773 
psycho_acoustic_model(s, smr[i]); 
774 
} 
775 
compute_bit_allocation(s, smr, bit_alloc, &padding); 
776  
777 
init_put_bits(&s>pb, frame, MPA_MAX_CODED_FRAME_SIZE); 
778  
779 
encode_frame(s, bit_alloc, padding); 
780  
781 
s>nb_samples += MPA_FRAME_SIZE; 
782 
return pbBufPtr(&s>pb)  s>pb.buf;

783 
} 
784  
785 
static int MPA_encode_close(AVCodecContext *avctx) 
786 
{ 
787 
av_freep(&avctx>coded_frame); 
788 
return 0; 
789 
} 
790  
791 
AVCodec mp2_encoder = { 
792 
"mp2",

793 
CODEC_TYPE_AUDIO, 
794 
CODEC_ID_MP2, 
795 
sizeof(MpegAudioContext),

796 
MPA_encode_init, 
797 
MPA_encode_frame, 
798 
MPA_encode_close, 
799 
NULL,

800 
}; 
801  
802 
#undef FIX
