FFmpeg: libavcodec/alac.c Source File

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libavcodec

alac.c

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1 /*

2 * ALAC (Apple Lossless Audio Codec) decoder

4 *

5 * This file is part of FFmpeg.

6 *

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

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

9 * License as published by the Free Software Foundation; either

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

11 *

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

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

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

15 * Lesser General Public License for more details.

16 *

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

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

19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

20 */

22 /**

23 * @file

24 * ALAC (Apple Lossless Audio Codec) decoder

25 * @author 2005 David Hammerton

26 * @see http://crazney.net/programs/itunes/alac.html

27 *

28 * Note: This decoder expects a 36-byte QuickTime atom to be

29 * passed through the extradata[_size] fields. This atom is tacked onto

30 * the end of an 'alac' stsd atom and has the following format:

31 *

32 * 32bit atom size

33 * 32bit tag ("alac")

34 * 32bit tag version (0)

35 * 32bit samples per frame (used when not set explicitly in the frames)

36 * 8bit compatible version (0)

37 * 8bit sample size

38 * 8bit history mult (40)

39 * 8bit initial history (10)

40 * 8bit rice param limit (14)

41 * 8bit channels

42 * 16bit maxRun (255)

43 * 32bit max coded frame size (0 means unknown)

44 * 32bit average bitrate (0 means unknown)

45 * 32bit samplerate

46 */

48 #include "libavutil/channel_layout.h"

49 #include "avcodec.h"

50 #include "get_bits.h"

51 #include "bytestream.h"

52 #include "internal.h"

53 #include "thread.h"

54 #include "unary.h"

55 #include "mathops.h"

56 #include "alac_data.h"

58 #define ALAC_EXTRADATA_SIZE 36

60 typedef struct {

61 AVCodecContext *avctx;

62 GetBitContext gb;

63 int channels;

65 int32_t *predict_error_buffer[2];

66 int32_t *output_samples_buffer[2];

67 int32_t *extra_bits_buffer[2];

69 uint32_t max_samples_per_frame;

70 uint8_t sample_size;

71 uint8_t rice_history_mult;

72 uint8_t rice_initial_history;

73 uint8_t rice_limit;

75 int extra_bits; /**< number of extra bits beyond 16-bit */

76 int nb_samples; /**< number of samples in the current frame */

78 int direct_output;

79 } ALACContext;

81 static inline unsigned int decode_scalar(GetBitContext *gb, int k, int bps)

82 {

83 unsigned int x = get_unary_0_9(gb);

85 if (x > 8) { /* RICE THRESHOLD */

86 /* use alternative encoding */

87 x = get_bits_long(gb, bps);

88 } else if (k != 1) {

89 int extrabits = show_bits(gb, k);

91 /* multiply x by 2^k - 1, as part of their strange algorithm */

92 x = (x << k) - x;

94 if (extrabits > 1) {

95 x += extrabits - 1;

96 skip_bits(gb, k);

97 } else

98 skip_bits(gb, k - 1);

99 }

100 return x;

101 }

102

103 static int rice_decompress(ALACContext *alac, int32_t *output_buffer,

104 int nb_samples, int bps, int rice_history_mult)

105 {

106 int i;

107 unsigned int history = alac->rice_initial_history;

108 int sign_modifier = 0;

109

110 for (i = 0; i < nb_samples; i++) {

111 int k;

112 unsigned int x;

113

114 if(get_bits_left(&alac->gb) <= 0)

115 return -1;

116

117 /* calculate rice param and decode next value */

118 k = av_log2((history >> 9) + 3);

119 k = FFMIN(k, alac->rice_limit);

120 x = decode_scalar(&alac->gb, k, bps);

121 x += sign_modifier;

122 sign_modifier = 0;

123 output_buffer[i] = (x >> 1) ^ -(x & 1);

124

125 /* update the history */

126 if (x > 0xffff)

127 history = 0xffff;

128 else

129 history += x * rice_history_mult -

130 ((history * rice_history_mult) >> 9);

131

132 /* special case: there may be compressed blocks of 0 */

133 if ((history < 128) && (i + 1 < nb_samples)) {

134 int block_size;

135

136 /* calculate rice param and decode block size */

137 k = 7 - av_log2(history) + ((history + 16) >> 6);

138 k = FFMIN(k, alac->rice_limit);

139 block_size = decode_scalar(&alac->gb, k, 16);

140

141 if (block_size > 0) {

142 if (block_size >= nb_samples - i) {

143 av_log(alac->avctx, AV_LOG_ERROR,

144 "invalid zero block size of %d %d %d\n", block_size,

145 nb_samples, i);

146 block_size = nb_samples - i - 1;

147 }

148 memset(&output_buffer[i + 1], 0,

149 block_size * sizeof(*output_buffer));

150 i += block_size;

151 }

152 if (block_size <= 0xffff)

153 sign_modifier = 1;

154 history = 0;

155 }

156 }

157 return 0;

158 }

159

160 static inline int sign_only(int v)

161 {

162 return v ? FFSIGN(v) : 0;

163 }

164

165 static void lpc_prediction(int32_t *error_buffer, int32_t *buffer_out,

166 int nb_samples, int bps, int16_t *lpc_coefs,

167 int lpc_order, int lpc_quant)

168 {

169 int i;

170 int32_t *pred = buffer_out;

171

172 /* first sample always copies */

173 *buffer_out = *error_buffer;

174

175 if (nb_samples <= 1)

176 return;

177

178 if (!lpc_order) {

179 memcpy(&buffer_out[1], &error_buffer[1],

180 (nb_samples - 1) * sizeof(*buffer_out));

181 return;

182 }

183

184 if (lpc_order == 31) {

185 /* simple 1st-order prediction */

186 for (i = 1; i < nb_samples; i++) {

187 buffer_out[i] = sign_extend(buffer_out[i - 1] + error_buffer[i],

188 bps);

189 }

190 return;

191 }

192

193 /* read warm-up samples */

194 for (i = 1; i <= lpc_order && i < nb_samples; i++)

195 buffer_out[i] = sign_extend(buffer_out[i - 1] + error_buffer[i], bps);

196

197 /* NOTE: 4 and 8 are very common cases that could be optimized. */

198

199 for (; i < nb_samples; i++) {

200 int j;

201 int val = 0;

202 int error_val = error_buffer[i];

203 int error_sign;

204 int d = *pred++;

205

206 /* LPC prediction */

207 for (j = 0; j < lpc_order; j++)

208 val += (pred[j] - d) * lpc_coefs[j];

209 val = (val + (1 << (lpc_quant - 1))) >> lpc_quant;

210 val += d + error_val;

211 buffer_out[i] = sign_extend(val, bps);

212

213 /* adapt LPC coefficients */

214 error_sign = sign_only(error_val);

215 if (error_sign) {

216 for (j = 0; j < lpc_order && error_val * error_sign > 0; j++) {

217 int sign;

218 val = d - pred[j];

219 sign = sign_only(val) * error_sign;

220 lpc_coefs[j] -= sign;

221 val *= sign;

222 error_val -= (val >> lpc_quant) * (j + 1);

223 }

224 }

225 }

226 }

227

228 static void decorrelate_stereo(int32_t *buffer[2], int nb_samples,

229 int decorr_shift, int decorr_left_weight)

230 {

231 int i;

232

233 for (i = 0; i < nb_samples; i++) {

234 int32_t a, b;

235

236 a = buffer[0][i];

237 b = buffer[1][i];

238

239 a -= (b * decorr_left_weight) >> decorr_shift;

240 b += a;

241

242 buffer[0][i] = b;

243 buffer[1][i] = a;

244 }

245 }

246

247 static void append_extra_bits(int32_t *buffer[2], int32_t *extra_bits_buffer[2],

248 int extra_bits, int channels, int nb_samples)

249 {

250 int i, ch;

251

252 for (ch = 0; ch < channels; ch++)

253 for (i = 0; i < nb_samples; i++)

254 buffer[ch][i] = (buffer[ch][i] << extra_bits) | extra_bits_buffer[ch][i];

255 }

256

257 static int decode_element(AVCodecContext *avctx, AVFrame *frame, int ch_index,

258 int channels)

259 {

260 ALACContext *alac = avctx->priv_data;

261 int has_size, bps, is_compressed, decorr_shift, decorr_left_weight, ret;

262 uint32_t output_samples;

263 int i, ch;

264

265 skip_bits(&alac->gb, 4); /* element instance tag */

266 skip_bits(&alac->gb, 12); /* unused header bits */

267

268 /* the number of output samples is stored in the frame */

269 has_size = get_bits1(&alac->gb);

270

271 alac->extra_bits = get_bits(&alac->gb, 2) << 3;

272 bps = alac->sample_size - alac->extra_bits + channels - 1;

273 if (bps > 32U) {

274 av_log(avctx, AV_LOG_ERROR, "bps is unsupported: %d\n", bps);

275 return AVERROR_PATCHWELCOME;

276 }

277

278 /* whether the frame is compressed */

279 is_compressed = !get_bits1(&alac->gb);

280

281 if (has_size)

282 output_samples = get_bits_long(&alac->gb, 32);

283 else

284 output_samples = alac->max_samples_per_frame;

285 if (!output_samples || output_samples > alac->max_samples_per_frame) {

286 av_log(avctx, AV_LOG_ERROR, "invalid samples per frame: %d\n",

287 output_samples);

288 return AVERROR_INVALIDDATA;

289 }

290 if (!alac->nb_samples) {

291 ThreadFrame tframe = { .f = frame };

292 /* get output buffer */

293 frame->nb_samples = output_samples;

294 if ((ret = ff_thread_get_buffer(avctx, &tframe, 0)) < 0)

295 return ret;

296 } else if (output_samples != alac->nb_samples) {

297 av_log(avctx, AV_LOG_ERROR, "sample count mismatch: %u != %d\n",

298 output_samples, alac->nb_samples);

299 return AVERROR_INVALIDDATA;

300 }

301 alac->nb_samples = output_samples;

302 if (alac->direct_output) {

303 for (ch = 0; ch < channels; ch++)

304 alac->output_samples_buffer[ch] = (int32_t *)frame->extended_data[ch_index + ch];

305 }

306

307 if (is_compressed) {

308 int16_t lpc_coefs[2][32];

309 int lpc_order[2];

310 int prediction_type[2];

311 int lpc_quant[2];

312 int rice_history_mult[2];

313

314 decorr_shift = get_bits(&alac->gb, 8);

315 decorr_left_weight = get_bits(&alac->gb, 8);

316

317 for (ch = 0; ch < channels; ch++) {

318 prediction_type[ch] = get_bits(&alac->gb, 4);

319 lpc_quant[ch] = get_bits(&alac->gb, 4);

320 rice_history_mult[ch] = get_bits(&alac->gb, 3);

321 lpc_order[ch] = get_bits(&alac->gb, 5);

322

323 if (lpc_order[ch] >= alac->max_samples_per_frame)

324 return AVERROR_INVALIDDATA;

325

326 /* read the predictor table */

327 for (i = lpc_order[ch] - 1; i >= 0; i--)

328 lpc_coefs[ch][i] = get_sbits(&alac->gb, 16);

329 }

330

331 if (alac->extra_bits) {

332 for (i = 0; i < alac->nb_samples; i++) {

333 if(get_bits_left(&alac->gb) <= 0)

334 return -1;

335 for (ch = 0; ch < channels; ch++)

336 alac->extra_bits_buffer[ch][i] = get_bits(&alac->gb, alac->extra_bits);

337 }

338 }

339 for (ch = 0; ch < channels; ch++) {

340 int ret=rice_decompress(alac, alac->predict_error_buffer[ch],

341 alac->nb_samples, bps,

342 rice_history_mult[ch] * alac->rice_history_mult / 4);

343 if(ret<0)

344 return ret;

345

346 /* adaptive FIR filter */

347 if (prediction_type[ch] == 15) {

348 /* Prediction type 15 runs the adaptive FIR twice.

349 * The first pass uses the special-case coef_num = 31, while

350 * the second pass uses the coefs from the bitstream.

351 *

352 * However, this prediction type is not currently used by the

353 * reference encoder.

354 */

355 lpc_prediction(alac->predict_error_buffer[ch],

356 alac->predict_error_buffer[ch],

357 alac->nb_samples, bps, NULL, 31, 0);

358 } else if (prediction_type[ch] > 0) {

359 av_log(avctx, AV_LOG_WARNING, "unknown prediction type: %i\n",

360 prediction_type[ch]);

361 }

362 lpc_prediction(alac->predict_error_buffer[ch],

363 alac->output_samples_buffer[ch], alac->nb_samples,

364 bps, lpc_coefs[ch], lpc_order[ch], lpc_quant[ch]);

365 }

366 } else {

367 /* not compressed, easy case */

368 for (i = 0; i < alac->nb_samples; i++) {

369 if(get_bits_left(&alac->gb) <= 0)

370 return -1;

371 for (ch = 0; ch < channels; ch++) {

372 alac->output_samples_buffer[ch][i] =

373 get_sbits_long(&alac->gb, alac->sample_size);

374 }

375 }

376 alac->extra_bits = 0;

377 decorr_shift = 0;

378 decorr_left_weight = 0;

379 }

380

381 if (channels == 2 && decorr_left_weight) {

382 decorrelate_stereo(alac->output_samples_buffer, alac->nb_samples,

383 decorr_shift, decorr_left_weight);

384 }

385

386 if (alac->extra_bits) {

387 append_extra_bits(alac->output_samples_buffer, alac->extra_bits_buffer,

388 alac->extra_bits, channels, alac->nb_samples);

389 }

390

391 if(av_sample_fmt_is_planar(avctx->sample_fmt)) {

392 switch(alac->sample_size) {

393 case 16: {

394 for (ch = 0; ch < channels; ch++) {

395 int16_t *outbuffer = (int16_t *)frame->extended_data[ch_index + ch];

396 for (i = 0; i < alac->nb_samples; i++)

397 *outbuffer++ = alac->output_samples_buffer[ch][i];

398 }}

399 break;

400 case 24: {

401 for (ch = 0; ch < channels; ch++) {

402 for (i = 0; i < alac->nb_samples; i++)

403 alac->output_samples_buffer[ch][i] <<= 8;

404 }}

405 break;

406 }

407 }else{

408 switch(alac->sample_size) {

409 case 16: {

410 int16_t *outbuffer = ((int16_t *)frame->extended_data[0]) + ch_index;

411 for (i = 0; i < alac->nb_samples; i++) {

412 for (ch = 0; ch < channels; ch++)

413 *outbuffer++ = alac->output_samples_buffer[ch][i];

414 outbuffer += alac->channels - channels;

415 }

416 }

417 break;

418 case 24: {

419 int32_t *outbuffer = ((int32_t *)frame->extended_data[0]) + ch_index;

420 for (i = 0; i < alac->nb_samples; i++) {

421 for (ch = 0; ch < channels; ch++)

422 *outbuffer++ = alac->output_samples_buffer[ch][i] << 8;

423 outbuffer += alac->channels - channels;

424 }

425 }

426 break;

427 case 32: {

428 int32_t *outbuffer = ((int32_t *)frame->extended_data[0]) + ch_index;

429 for (i = 0; i < alac->nb_samples; i++) {

430 for (ch = 0; ch < channels; ch++)

431 *outbuffer++ = alac->output_samples_buffer[ch][i];

432 outbuffer += alac->channels - channels;

433 }

434 }

435 break;

436 }

437 }

438

439 return 0;

440 }

441

442 static int alac_decode_frame(AVCodecContext *avctx, void *data,

443 int *got_frame_ptr, AVPacket *avpkt)

444 {

445 ALACContext *alac = avctx->priv_data;

446 AVFrame *frame = data;

447 enum AlacRawDataBlockType element;

448 int channels;

449 int ch, ret, got_end;

450

451 if ((ret = init_get_bits8(&alac->gb, avpkt->data, avpkt->size)) < 0)

452 return ret;

453

454 got_end = 0;

455 alac->nb_samples = 0;

456 ch = 0;

457 while (get_bits_left(&alac->gb) >= 3) {

458 element = get_bits(&alac->gb, 3);

459 if (element == TYPE_END) {

460 got_end = 1;

461 break;

462 }

463 if (element > TYPE_CPE && element != TYPE_LFE) {

464 av_log(avctx, AV_LOG_ERROR, "syntax element unsupported: %d\n", element);

465 return AVERROR_PATCHWELCOME;

466 }

467

468 channels = (element == TYPE_CPE) ? 2 : 1;

469 if (ch + channels > alac->channels ||

470 ff_alac_channel_layout_offsets[alac->channels - 1][ch] + channels > alac->channels) {

471 av_log(avctx, AV_LOG_ERROR, "invalid element channel count\n");

472 return AVERROR_INVALIDDATA;

473 }

474

475 ret = decode_element(avctx, frame,

476 ff_alac_channel_layout_offsets[alac->channels - 1][ch],

477 channels);

478 if (ret < 0 && get_bits_left(&alac->gb))

479 return ret;

480

481 ch += channels;

482 }

483 if (!got_end) {

484 av_log(avctx, AV_LOG_ERROR, "no end tag found. incomplete packet.\n");

485 return AVERROR_INVALIDDATA;

486 }

487

488 if (avpkt->size * 8 - get_bits_count(&alac->gb) > 8) {

489 av_log(avctx, AV_LOG_ERROR, "Error : %d bits left\n",

490 avpkt->size * 8 - get_bits_count(&alac->gb));

491 }

492

493 if (alac->channels == ch)

494 *got_frame_ptr = 1;

495

496 return avpkt->size;

497 }

498

499 static av_cold int alac_decode_close(AVCodecContext *avctx)

500 {

501 ALACContext *alac = avctx->priv_data;

502

503 int ch;

504 for (ch = 0; ch < FFMIN(alac->channels, 2); ch++) {

505 av_freep(&alac->predict_error_buffer[ch]);

506 if (!alac->direct_output)

507 av_freep(&alac->output_samples_buffer[ch]);

508 av_freep(&alac->extra_bits_buffer[ch]);

509 }

510

511 return 0;

512 }

513

514 static int allocate_buffers(ALACContext *alac)

515 {

516 int ch;

517 int buf_size = alac->max_samples_per_frame * sizeof(int32_t);

518

519 for (ch = 0; ch < FFMIN(alac->channels, 2); ch++) {

520 FF_ALLOC_OR_GOTO(alac->avctx, alac->predict_error_buffer[ch],

521 buf_size, buf_alloc_fail);

522

523 alac->direct_output = alac->sample_size > 16 && av_sample_fmt_is_planar(alac->avctx->sample_fmt);

524 if (!alac->direct_output) {

525 FF_ALLOC_OR_GOTO(alac->avctx, alac->output_samples_buffer[ch],

526 buf_size, buf_alloc_fail);

527 }

528

529 FF_ALLOC_OR_GOTO(alac->avctx, alac->extra_bits_buffer[ch],

530 buf_size, buf_alloc_fail);

531 }

532 return 0;

533 buf_alloc_fail:

534 alac_decode_close(alac->avctx);

535 return AVERROR(ENOMEM);

536 }

537

538 static int alac_set_info(ALACContext *alac)

539 {

540 GetByteContext gb;

541

542 bytestream2_init(&gb, alac->avctx->extradata,

543 alac->avctx->extradata_size);

544

545 bytestream2_skipu(&gb, 12); // size:4, alac:4, version:4

546

547 alac->max_samples_per_frame = bytestream2_get_be32u(&gb);

548 if (!alac->max_samples_per_frame ||

549 alac->max_samples_per_frame > INT_MAX / sizeof(int32_t)) {

550 av_log(alac->avctx, AV_LOG_ERROR, "max samples per frame invalid: %u\n",

551 alac->max_samples_per_frame);

552 return AVERROR_INVALIDDATA;

553 }

554 bytestream2_skipu(&gb, 1); // compatible version

555 alac->sample_size = bytestream2_get_byteu(&gb);

556 alac->rice_history_mult = bytestream2_get_byteu(&gb);

557 alac->rice_initial_history = bytestream2_get_byteu(&gb);

558 alac->rice_limit = bytestream2_get_byteu(&gb);

559 alac->channels = bytestream2_get_byteu(&gb);

560 bytestream2_get_be16u(&gb); // maxRun

561 bytestream2_get_be32u(&gb); // max coded frame size

562 bytestream2_get_be32u(&gb); // average bitrate

563 bytestream2_get_be32u(&gb); // samplerate

564

565 return 0;

566 }

567

568 static av_cold int alac_decode_init(AVCodecContext * avctx)

569 {

570 int ret;

571 int req_packed;

572 ALACContext *alac = avctx->priv_data;

573 alac->avctx = avctx;

574

575 /* initialize from the extradata */

576 if (alac->avctx->extradata_size < ALAC_EXTRADATA_SIZE) {

577 av_log(avctx, AV_LOG_ERROR, "extradata is too small\n");

578 return AVERROR_INVALIDDATA;

579 }

580 if (alac_set_info(alac)) {

581 av_log(avctx, AV_LOG_ERROR, "set_info failed\n");

582 return -1;

583 }

584

585 req_packed = LIBAVCODEC_VERSION_MAJOR < 55 && !av_sample_fmt_is_planar(avctx->request_sample_fmt);

586 switch (alac->sample_size) {

587 case 16: avctx->sample_fmt = req_packed ? AV_SAMPLE_FMT_S16 : AV_SAMPLE_FMT_S16P;

588 break;

589 case 24:

590 case 32: avctx->sample_fmt = req_packed ? AV_SAMPLE_FMT_S32 : AV_SAMPLE_FMT_S32P;

591 break;

592 default: avpriv_request_sample(avctx, "Sample depth %d", alac->sample_size);

593 return AVERROR_PATCHWELCOME;

594 }

595 avctx->bits_per_raw_sample = alac->sample_size;

596

597 if (alac->channels < 1) {

598 av_log(avctx, AV_LOG_WARNING, "Invalid channel count\n");

599 alac->channels = avctx->channels;

600 } else {

601 if (alac->channels > ALAC_MAX_CHANNELS)

602 alac->channels = avctx->channels;

603 else

604 avctx->channels = alac->channels;

605 }

606 if (avctx->channels > ALAC_MAX_CHANNELS || avctx->channels <= 0 ) {

607 av_log(avctx, AV_LOG_ERROR, "Unsupported channel count: %d\n",

608 avctx->channels);

609 return AVERROR_PATCHWELCOME;

610 }

611 avctx->channel_layout = ff_alac_channel_layouts[alac->channels - 1];

612

613 if ((ret = allocate_buffers(alac)) < 0) {

614 av_log(avctx, AV_LOG_ERROR, "Error allocating buffers\n");

615 return ret;

616 }

617

618 return 0;

619 }

620

621 static int init_thread_copy(AVCodecContext *avctx)

622 {

623 ALACContext *alac = avctx->priv_data;

624 alac->avctx = avctx;

625 return allocate_buffers(alac);

626 }

627

628 AVCodec ff_alac_decoder = {

629 .name = "alac",

630 .long_name = NULL_IF_CONFIG_SMALL("ALAC (Apple Lossless Audio Codec)"),

631 .type = AVMEDIA_TYPE_AUDIO,

632 .id = AV_CODEC_ID_ALAC,

633 .priv_data_size = sizeof(ALACContext),

634 .init = alac_decode_init,

635 .close = alac_decode_close,

636 .decode = alac_decode_frame,

637 .init_thread_copy = ONLY_IF_THREADS_ENABLED(init_thread_copy),

638 .capabilities = CODEC_CAP_DR1 | CODEC_CAP_FRAME_THREADS,

639 };

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