1 /* 2 * Copyright (C) 2010 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 //#define LOG_NDEBUG 0 18 #define LOG_TAG "avc_utils" 19 #include <utils/Log.h> 20 21 #include "include/avc_utils.h" 22 23 #include <media/stagefright/foundation/ABitReader.h> 24 #include <media/stagefright/foundation/ADebug.h> 25 #include <media/stagefright/foundation/hexdump.h> 26 #include <media/stagefright/MediaDefs.h> 27 #include <media/stagefright/MediaErrors.h> 28 #include <media/stagefright/MetaData.h> 29 30 namespace android { 31 32 unsigned parseUE(ABitReader *br) { 33 unsigned numZeroes = 0; 34 while (br->getBits(1) == 0) { 35 ++numZeroes; 36 } 37 38 unsigned x = br->getBits(numZeroes); 39 40 return x + (1u << numZeroes) - 1; 41 } 42 43 signed parseSE(ABitReader *br) { 44 unsigned codeNum = parseUE(br); 45 46 return (codeNum & 1) ? (codeNum + 1) / 2 : -(codeNum / 2); 47 } 48 49 static void skipScalingList(ABitReader *br, size_t sizeOfScalingList) { 50 size_t lastScale = 8; 51 size_t nextScale = 8; 52 for (size_t j = 0; j < sizeOfScalingList; ++j) { 53 if (nextScale != 0) { 54 signed delta_scale = parseSE(br); 55 nextScale = (lastScale + delta_scale + 256) % 256; 56 } 57 58 lastScale = (nextScale == 0) ? lastScale : nextScale; 59 } 60 } 61 62 // Determine video dimensions from the sequence parameterset. 63 void FindAVCDimensions( 64 const sp<ABuffer> &seqParamSet, 65 int32_t *width, int32_t *height, 66 int32_t *sarWidth, int32_t *sarHeight) { 67 ABitReader br(seqParamSet->data() + 1, seqParamSet->size() - 1); 68 69 unsigned profile_idc = br.getBits(8); 70 br.skipBits(16); 71 parseUE(&br); // seq_parameter_set_id 72 73 unsigned chroma_format_idc = 1; // 4:2:0 chroma format 74 75 if (profile_idc == 100 || profile_idc == 110 76 || profile_idc == 122 || profile_idc == 244 77 || profile_idc == 44 || profile_idc == 83 || profile_idc == 86) { 78 chroma_format_idc = parseUE(&br); 79 if (chroma_format_idc == 3) { 80 br.skipBits(1); // residual_colour_transform_flag 81 } 82 parseUE(&br); // bit_depth_luma_minus8 83 parseUE(&br); // bit_depth_chroma_minus8 84 br.skipBits(1); // qpprime_y_zero_transform_bypass_flag 85 86 if (br.getBits(1)) { // seq_scaling_matrix_present_flag 87 for (size_t i = 0; i < 8; ++i) { 88 if (br.getBits(1)) { // seq_scaling_list_present_flag[i] 89 90 // WARNING: the code below has not ever been exercised... 91 // need a real-world example. 92 93 if (i < 6) { 94 // ScalingList4x4[i],16,... 95 skipScalingList(&br, 16); 96 } else { 97 // ScalingList8x8[i-6],64,... 98 skipScalingList(&br, 64); 99 } 100 } 101 } 102 } 103 } 104 105 parseUE(&br); // log2_max_frame_num_minus4 106 unsigned pic_order_cnt_type = parseUE(&br); 107 108 if (pic_order_cnt_type == 0) { 109 parseUE(&br); // log2_max_pic_order_cnt_lsb_minus4 110 } else if (pic_order_cnt_type == 1) { 111 // offset_for_non_ref_pic, offset_for_top_to_bottom_field and 112 // offset_for_ref_frame are technically se(v), but since we are 113 // just skipping over them the midpoint does not matter. 114 115 br.getBits(1); // delta_pic_order_always_zero_flag 116 parseUE(&br); // offset_for_non_ref_pic 117 parseUE(&br); // offset_for_top_to_bottom_field 118 119 unsigned num_ref_frames_in_pic_order_cnt_cycle = parseUE(&br); 120 for (unsigned i = 0; i < num_ref_frames_in_pic_order_cnt_cycle; ++i) { 121 parseUE(&br); // offset_for_ref_frame 122 } 123 } 124 125 parseUE(&br); // num_ref_frames 126 br.getBits(1); // gaps_in_frame_num_value_allowed_flag 127 128 unsigned pic_width_in_mbs_minus1 = parseUE(&br); 129 unsigned pic_height_in_map_units_minus1 = parseUE(&br); 130 unsigned frame_mbs_only_flag = br.getBits(1); 131 132 *width = pic_width_in_mbs_minus1 * 16 + 16; 133 134 *height = (2 - frame_mbs_only_flag) 135 * (pic_height_in_map_units_minus1 * 16 + 16); 136 137 if (!frame_mbs_only_flag) { 138 br.getBits(1); // mb_adaptive_frame_field_flag 139 } 140 141 br.getBits(1); // direct_8x8_inference_flag 142 143 if (br.getBits(1)) { // frame_cropping_flag 144 unsigned frame_crop_left_offset = parseUE(&br); 145 unsigned frame_crop_right_offset = parseUE(&br); 146 unsigned frame_crop_top_offset = parseUE(&br); 147 unsigned frame_crop_bottom_offset = parseUE(&br); 148 149 unsigned cropUnitX, cropUnitY; 150 if (chroma_format_idc == 0 /* monochrome */) { 151 cropUnitX = 1; 152 cropUnitY = 2 - frame_mbs_only_flag; 153 } else { 154 unsigned subWidthC = (chroma_format_idc == 3) ? 1 : 2; 155 unsigned subHeightC = (chroma_format_idc == 1) ? 2 : 1; 156 157 cropUnitX = subWidthC; 158 cropUnitY = subHeightC * (2 - frame_mbs_only_flag); 159 } 160 161 ALOGV("frame_crop = (%u, %u, %u, %u), cropUnitX = %u, cropUnitY = %u", 162 frame_crop_left_offset, frame_crop_right_offset, 163 frame_crop_top_offset, frame_crop_bottom_offset, 164 cropUnitX, cropUnitY); 165 166 *width -= 167 (frame_crop_left_offset + frame_crop_right_offset) * cropUnitX; 168 *height -= 169 (frame_crop_top_offset + frame_crop_bottom_offset) * cropUnitY; 170 } 171 172 if (sarWidth != NULL) { 173 *sarWidth = 0; 174 } 175 176 if (sarHeight != NULL) { 177 *sarHeight = 0; 178 } 179 180 if (br.getBits(1)) { // vui_parameters_present_flag 181 unsigned sar_width = 0, sar_height = 0; 182 183 if (br.getBits(1)) { // aspect_ratio_info_present_flag 184 unsigned aspect_ratio_idc = br.getBits(8); 185 186 if (aspect_ratio_idc == 255 /* extendedSAR */) { 187 sar_width = br.getBits(16); 188 sar_height = br.getBits(16); 189 } else if (aspect_ratio_idc > 0 && aspect_ratio_idc < 14) { 190 static const int32_t kFixedSARWidth[] = { 191 1, 12, 10, 16, 40, 24, 20, 32, 80, 18, 15, 64, 160 192 }; 193 194 static const int32_t kFixedSARHeight[] = { 195 1, 11, 11, 11, 33, 11, 11, 11, 33, 11, 11, 33, 99 196 }; 197 198 sar_width = kFixedSARWidth[aspect_ratio_idc - 1]; 199 sar_height = kFixedSARHeight[aspect_ratio_idc - 1]; 200 } 201 } 202 203 ALOGV("sample aspect ratio = %u : %u", sar_width, sar_height); 204 205 if (sarWidth != NULL) { 206 *sarWidth = sar_width; 207 } 208 209 if (sarHeight != NULL) { 210 *sarHeight = sar_height; 211 } 212 } 213 } 214 215 status_t getNextNALUnit( 216 const uint8_t **_data, size_t *_size, 217 const uint8_t **nalStart, size_t *nalSize, 218 bool startCodeFollows) { 219 const uint8_t *data = *_data; 220 size_t size = *_size; 221 222 *nalStart = NULL; 223 *nalSize = 0; 224 225 if (size == 0) { 226 return -EAGAIN; 227 } 228 229 // Skip any number of leading 0x00. 230 231 size_t offset = 0; 232 while (offset < size && data[offset] == 0x00) { 233 ++offset; 234 } 235 236 if (offset == size) { 237 return -EAGAIN; 238 } 239 240 // A valid startcode consists of at least two 0x00 bytes followed by 0x01. 241 242 if (offset < 2 || data[offset] != 0x01) { 243 return ERROR_MALFORMED; 244 } 245 246 ++offset; 247 248 size_t startOffset = offset; 249 250 for (;;) { 251 while (offset < size && data[offset] != 0x01) { 252 ++offset; 253 } 254 255 if (offset == size) { 256 if (startCodeFollows) { 257 offset = size + 2; 258 break; 259 } 260 261 return -EAGAIN; 262 } 263 264 if (data[offset - 1] == 0x00 && data[offset - 2] == 0x00) { 265 break; 266 } 267 268 ++offset; 269 } 270 271 size_t endOffset = offset - 2; 272 while (endOffset > startOffset + 1 && data[endOffset - 1] == 0x00) { 273 --endOffset; 274 } 275 276 *nalStart = &data[startOffset]; 277 *nalSize = endOffset - startOffset; 278 279 if (offset + 2 < size) { 280 *_data = &data[offset - 2]; 281 *_size = size - offset + 2; 282 } else { 283 *_data = NULL; 284 *_size = 0; 285 } 286 287 return OK; 288 } 289 290 static sp<ABuffer> FindNAL(const uint8_t *data, size_t size, unsigned nalType) { 291 const uint8_t *nalStart; 292 size_t nalSize; 293 while (getNextNALUnit(&data, &size, &nalStart, &nalSize, true) == OK) { 294 if ((nalStart[0] & 0x1f) == nalType) { 295 sp<ABuffer> buffer = new ABuffer(nalSize); 296 memcpy(buffer->data(), nalStart, nalSize); 297 return buffer; 298 } 299 } 300 301 return NULL; 302 } 303 304 const char *AVCProfileToString(uint8_t profile) { 305 switch (profile) { 306 case kAVCProfileBaseline: 307 return "Baseline"; 308 case kAVCProfileMain: 309 return "Main"; 310 case kAVCProfileExtended: 311 return "Extended"; 312 case kAVCProfileHigh: 313 return "High"; 314 case kAVCProfileHigh10: 315 return "High 10"; 316 case kAVCProfileHigh422: 317 return "High 422"; 318 case kAVCProfileHigh444: 319 return "High 444"; 320 case kAVCProfileCAVLC444Intra: 321 return "CAVLC 444 Intra"; 322 default: return "Unknown"; 323 } 324 } 325 326 sp<MetaData> MakeAVCCodecSpecificData(const sp<ABuffer> &accessUnit) { 327 const uint8_t *data = accessUnit->data(); 328 size_t size = accessUnit->size(); 329 330 sp<ABuffer> seqParamSet = FindNAL(data, size, 7); 331 if (seqParamSet == NULL) { 332 return NULL; 333 } 334 335 int32_t width, height; 336 int32_t sarWidth, sarHeight; 337 FindAVCDimensions( 338 seqParamSet, &width, &height, &sarWidth, &sarHeight); 339 340 sp<ABuffer> picParamSet = FindNAL(data, size, 8); 341 CHECK(picParamSet != NULL); 342 343 size_t csdSize = 344 1 + 3 + 1 + 1 345 + 2 * 1 + seqParamSet->size() 346 + 1 + 2 * 1 + picParamSet->size(); 347 348 sp<ABuffer> csd = new ABuffer(csdSize); 349 uint8_t *out = csd->data(); 350 351 *out++ = 0x01; // configurationVersion 352 memcpy(out, seqParamSet->data() + 1, 3); // profile/level... 353 354 uint8_t profile = out[0]; 355 uint8_t level = out[2]; 356 357 out += 3; 358 *out++ = (0x3f << 2) | 1; // lengthSize == 2 bytes 359 *out++ = 0xe0 | 1; 360 361 *out++ = seqParamSet->size() >> 8; 362 *out++ = seqParamSet->size() & 0xff; 363 memcpy(out, seqParamSet->data(), seqParamSet->size()); 364 out += seqParamSet->size(); 365 366 *out++ = 1; 367 368 *out++ = picParamSet->size() >> 8; 369 *out++ = picParamSet->size() & 0xff; 370 memcpy(out, picParamSet->data(), picParamSet->size()); 371 372 #if 0 373 ALOGI("AVC seq param set"); 374 hexdump(seqParamSet->data(), seqParamSet->size()); 375 #endif 376 377 sp<MetaData> meta = new MetaData; 378 meta->setCString(kKeyMIMEType, MEDIA_MIMETYPE_VIDEO_AVC); 379 380 meta->setData(kKeyAVCC, kTypeAVCC, csd->data(), csd->size()); 381 meta->setInt32(kKeyWidth, width); 382 meta->setInt32(kKeyHeight, height); 383 384 if (sarWidth > 1 || sarHeight > 1) { 385 // We treat 0:0 (unspecified) as 1:1. 386 387 meta->setInt32(kKeySARWidth, sarWidth); 388 meta->setInt32(kKeySARHeight, sarHeight); 389 390 ALOGI("found AVC codec config (%d x %d, %s-profile level %d.%d) " 391 "SAR %d : %d", 392 width, 393 height, 394 AVCProfileToString(profile), 395 level / 10, 396 level % 10, 397 sarWidth, 398 sarHeight); 399 } else { 400 ALOGI("found AVC codec config (%d x %d, %s-profile level %d.%d)", 401 width, 402 height, 403 AVCProfileToString(profile), 404 level / 10, 405 level % 10); 406 } 407 408 return meta; 409 } 410 411 bool IsIDR(const sp<ABuffer> &buffer) { 412 const uint8_t *data = buffer->data(); 413 size_t size = buffer->size(); 414 415 bool foundIDR = false; 416 417 const uint8_t *nalStart; 418 size_t nalSize; 419 while (getNextNALUnit(&data, &size, &nalStart, &nalSize, true) == OK) { 420 CHECK_GT(nalSize, 0u); 421 422 unsigned nalType = nalStart[0] & 0x1f; 423 424 if (nalType == 5) { 425 foundIDR = true; 426 break; 427 } 428 } 429 430 return foundIDR; 431 } 432 433 bool IsAVCReferenceFrame(const sp<ABuffer> &accessUnit) { 434 const uint8_t *data = accessUnit->data(); 435 size_t size = accessUnit->size(); 436 437 const uint8_t *nalStart; 438 size_t nalSize; 439 while (getNextNALUnit(&data, &size, &nalStart, &nalSize, true) == OK) { 440 CHECK_GT(nalSize, 0u); 441 442 unsigned nalType = nalStart[0] & 0x1f; 443 444 if (nalType == 5) { 445 return true; 446 } else if (nalType == 1) { 447 unsigned nal_ref_idc = (nalStart[0] >> 5) & 3; 448 return nal_ref_idc != 0; 449 } 450 } 451 452 return true; 453 } 454 455 sp<MetaData> MakeAACCodecSpecificData( 456 unsigned profile, unsigned sampling_freq_index, 457 unsigned channel_configuration) { 458 sp<MetaData> meta = new MetaData; 459 meta->setCString(kKeyMIMEType, MEDIA_MIMETYPE_AUDIO_AAC); 460 461 CHECK_LE(sampling_freq_index, 11u); 462 static const int32_t kSamplingFreq[] = { 463 96000, 88200, 64000, 48000, 44100, 32000, 24000, 22050, 464 16000, 12000, 11025, 8000 465 }; 466 meta->setInt32(kKeySampleRate, kSamplingFreq[sampling_freq_index]); 467 meta->setInt32(kKeyChannelCount, channel_configuration); 468 469 static const uint8_t kStaticESDS[] = { 470 0x03, 22, 471 0x00, 0x00, // ES_ID 472 0x00, // streamDependenceFlag, URL_Flag, OCRstreamFlag 473 474 0x04, 17, 475 0x40, // Audio ISO/IEC 14496-3 476 0x00, 0x00, 0x00, 0x00, 477 0x00, 0x00, 0x00, 0x00, 478 0x00, 0x00, 0x00, 0x00, 479 480 0x05, 2, 481 // AudioSpecificInfo follows 482 483 // oooo offf fccc c000 484 // o - audioObjectType 485 // f - samplingFreqIndex 486 // c - channelConfig 487 }; 488 sp<ABuffer> csd = new ABuffer(sizeof(kStaticESDS) + 2); 489 memcpy(csd->data(), kStaticESDS, sizeof(kStaticESDS)); 490 491 csd->data()[sizeof(kStaticESDS)] = 492 ((profile + 1) << 3) | (sampling_freq_index >> 1); 493 494 csd->data()[sizeof(kStaticESDS) + 1] = 495 ((sampling_freq_index << 7) & 0x80) | (channel_configuration << 3); 496 497 meta->setData(kKeyESDS, 0, csd->data(), csd->size()); 498 499 return meta; 500 } 501 502 bool ExtractDimensionsFromVOLHeader( 503 const uint8_t *data, size_t size, int32_t *width, int32_t *height) { 504 ABitReader br(&data[4], size - 4); 505 br.skipBits(1); // random_accessible_vol 506 unsigned video_object_type_indication = br.getBits(8); 507 508 CHECK_NE(video_object_type_indication, 509 0x21u /* Fine Granularity Scalable */); 510 511 unsigned video_object_layer_verid; 512 unsigned video_object_layer_priority; 513 if (br.getBits(1)) { 514 video_object_layer_verid = br.getBits(4); 515 video_object_layer_priority = br.getBits(3); 516 } 517 unsigned aspect_ratio_info = br.getBits(4); 518 if (aspect_ratio_info == 0x0f /* extended PAR */) { 519 br.skipBits(8); // par_width 520 br.skipBits(8); // par_height 521 } 522 if (br.getBits(1)) { // vol_control_parameters 523 br.skipBits(2); // chroma_format 524 br.skipBits(1); // low_delay 525 if (br.getBits(1)) { // vbv_parameters 526 br.skipBits(15); // first_half_bit_rate 527 CHECK(br.getBits(1)); // marker_bit 528 br.skipBits(15); // latter_half_bit_rate 529 CHECK(br.getBits(1)); // marker_bit 530 br.skipBits(15); // first_half_vbv_buffer_size 531 CHECK(br.getBits(1)); // marker_bit 532 br.skipBits(3); // latter_half_vbv_buffer_size 533 br.skipBits(11); // first_half_vbv_occupancy 534 CHECK(br.getBits(1)); // marker_bit 535 br.skipBits(15); // latter_half_vbv_occupancy 536 CHECK(br.getBits(1)); // marker_bit 537 } 538 } 539 unsigned video_object_layer_shape = br.getBits(2); 540 CHECK_EQ(video_object_layer_shape, 0x00u /* rectangular */); 541 542 CHECK(br.getBits(1)); // marker_bit 543 unsigned vop_time_increment_resolution = br.getBits(16); 544 CHECK(br.getBits(1)); // marker_bit 545 546 if (br.getBits(1)) { // fixed_vop_rate 547 // range [0..vop_time_increment_resolution) 548 549 // vop_time_increment_resolution 550 // 2 => 0..1, 1 bit 551 // 3 => 0..2, 2 bits 552 // 4 => 0..3, 2 bits 553 // 5 => 0..4, 3 bits 554 // ... 555 556 CHECK_GT(vop_time_increment_resolution, 0u); 557 --vop_time_increment_resolution; 558 559 unsigned numBits = 0; 560 while (vop_time_increment_resolution > 0) { 561 ++numBits; 562 vop_time_increment_resolution >>= 1; 563 } 564 565 br.skipBits(numBits); // fixed_vop_time_increment 566 } 567 568 CHECK(br.getBits(1)); // marker_bit 569 unsigned video_object_layer_width = br.getBits(13); 570 CHECK(br.getBits(1)); // marker_bit 571 unsigned video_object_layer_height = br.getBits(13); 572 CHECK(br.getBits(1)); // marker_bit 573 574 unsigned interlaced = br.getBits(1); 575 576 *width = video_object_layer_width; 577 *height = video_object_layer_height; 578 579 return true; 580 } 581 582 bool GetMPEGAudioFrameSize( 583 uint32_t header, size_t *frame_size, 584 int *out_sampling_rate, int *out_channels, 585 int *out_bitrate, int *out_num_samples) { 586 *frame_size = 0; 587 588 if (out_sampling_rate) { 589 *out_sampling_rate = 0; 590 } 591 592 if (out_channels) { 593 *out_channels = 0; 594 } 595 596 if (out_bitrate) { 597 *out_bitrate = 0; 598 } 599 600 if (out_num_samples) { 601 *out_num_samples = 1152; 602 } 603 604 if ((header & 0xffe00000) != 0xffe00000) { 605 return false; 606 } 607 608 unsigned version = (header >> 19) & 3; 609 610 if (version == 0x01) { 611 return false; 612 } 613 614 unsigned layer = (header >> 17) & 3; 615 616 if (layer == 0x00) { 617 return false; 618 } 619 620 unsigned protection = (header >> 16) & 1; 621 622 unsigned bitrate_index = (header >> 12) & 0x0f; 623 624 if (bitrate_index == 0 || bitrate_index == 0x0f) { 625 // Disallow "free" bitrate. 626 return false; 627 } 628 629 unsigned sampling_rate_index = (header >> 10) & 3; 630 631 if (sampling_rate_index == 3) { 632 return false; 633 } 634 635 static const int kSamplingRateV1[] = { 44100, 48000, 32000 }; 636 int sampling_rate = kSamplingRateV1[sampling_rate_index]; 637 if (version == 2 /* V2 */) { 638 sampling_rate /= 2; 639 } else if (version == 0 /* V2.5 */) { 640 sampling_rate /= 4; 641 } 642 643 unsigned padding = (header >> 9) & 1; 644 645 if (layer == 3) { 646 // layer I 647 648 static const int kBitrateV1[] = { 649 32, 64, 96, 128, 160, 192, 224, 256, 650 288, 320, 352, 384, 416, 448 651 }; 652 653 static const int kBitrateV2[] = { 654 32, 48, 56, 64, 80, 96, 112, 128, 655 144, 160, 176, 192, 224, 256 656 }; 657 658 int bitrate = 659 (version == 3 /* V1 */) 660 ? kBitrateV1[bitrate_index - 1] 661 : kBitrateV2[bitrate_index - 1]; 662 663 if (out_bitrate) { 664 *out_bitrate = bitrate; 665 } 666 667 *frame_size = (12000 * bitrate / sampling_rate + padding) * 4; 668 669 if (out_num_samples) { 670 *out_num_samples = 384; 671 } 672 } else { 673 // layer II or III 674 675 static const int kBitrateV1L2[] = { 676 32, 48, 56, 64, 80, 96, 112, 128, 677 160, 192, 224, 256, 320, 384 678 }; 679 680 static const int kBitrateV1L3[] = { 681 32, 40, 48, 56, 64, 80, 96, 112, 682 128, 160, 192, 224, 256, 320 683 }; 684 685 static const int kBitrateV2[] = { 686 8, 16, 24, 32, 40, 48, 56, 64, 687 80, 96, 112, 128, 144, 160 688 }; 689 690 int bitrate; 691 if (version == 3 /* V1 */) { 692 bitrate = (layer == 2 /* L2 */) 693 ? kBitrateV1L2[bitrate_index - 1] 694 : kBitrateV1L3[bitrate_index - 1]; 695 696 if (out_num_samples) { 697 *out_num_samples = 1152; 698 } 699 } else { 700 // V2 (or 2.5) 701 702 bitrate = kBitrateV2[bitrate_index - 1]; 703 if (out_num_samples) { 704 *out_num_samples = (layer == 1 /* L3 */) ? 576 : 1152; 705 } 706 } 707 708 if (out_bitrate) { 709 *out_bitrate = bitrate; 710 } 711 712 if (version == 3 /* V1 */) { 713 *frame_size = 144000 * bitrate / sampling_rate + padding; 714 } else { 715 // V2 or V2.5 716 size_t tmp = (layer == 1 /* L3 */) ? 72000 : 144000; 717 *frame_size = tmp * bitrate / sampling_rate + padding; 718 } 719 } 720 721 if (out_sampling_rate) { 722 *out_sampling_rate = sampling_rate; 723 } 724 725 if (out_channels) { 726 int channel_mode = (header >> 6) & 3; 727 728 *out_channels = (channel_mode == 3) ? 1 : 2; 729 } 730 731 return true; 732 } 733 734 } // namespace android 735 736
