git.sesse.net Git - ffmpeg/blob - libavresample/utils.c

   1 /*
   2  * Copyright (c) 2012 Justin Ruggles <justin.ruggles@gmail.com>
   3  *
   4  * This file is part of Libav.
   5  *
   6  * Libav is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * Libav is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with Libav; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  19  */
  20
  21 #include "libavutil/common.h"
  22 #include "libavutil/dict.h"
  23 #include "libavutil/error.h"
  24 #include "libavutil/log.h"
  25 #include "libavutil/mem.h"
  26 #include "libavutil/opt.h"
  27
  28 #include "avresample.h"
  29 #include "internal.h"
  30 #include "audio_data.h"
  31 #include "audio_convert.h"
  32 #include "audio_mix.h"
  33 #include "resample.h"
  34
  35 int avresample_open(AVAudioResampleContext *avr)
  36 {
  37     int ret;
  38
  39     /* set channel mixing parameters */
  40     avr->in_channels = av_get_channel_layout_nb_channels(avr->in_channel_layout);
  41     if (avr->in_channels <= 0 || avr->in_channels > AVRESAMPLE_MAX_CHANNELS) {
  42         av_log(avr, AV_LOG_ERROR, "Invalid input channel layout: %"PRIu64"\n",
  43                avr->in_channel_layout);
  44         return AVERROR(EINVAL);
  45     }
  46     avr->out_channels = av_get_channel_layout_nb_channels(avr->out_channel_layout);
  47     if (avr->out_channels <= 0 || avr->out_channels > AVRESAMPLE_MAX_CHANNELS) {
  48         av_log(avr, AV_LOG_ERROR, "Invalid output channel layout: %"PRIu64"\n",
  49                avr->out_channel_layout);
  50         return AVERROR(EINVAL);
  51     }
  52     avr->resample_channels = FFMIN(avr->in_channels, avr->out_channels);
  53     avr->downmix_needed    = avr->in_channels  > avr->out_channels;
  54     avr->upmix_needed      = avr->out_channels > avr->in_channels ||
  55                              (!avr->downmix_needed && (avr->mix_matrix ||
  56                               avr->in_channel_layout != avr->out_channel_layout));
  57     avr->mixing_needed     = avr->downmix_needed || avr->upmix_needed;
  58
  59     /* set resampling parameters */
  60     avr->resample_needed   = avr->in_sample_rate != avr->out_sample_rate ||
  61                              avr->force_resampling;
  62
  63     /* select internal sample format if not specified by the user */
  64     if (avr->internal_sample_fmt == AV_SAMPLE_FMT_NONE &&
  65         (avr->mixing_needed || avr->resample_needed)) {
  66         enum AVSampleFormat  in_fmt = av_get_planar_sample_fmt(avr->in_sample_fmt);
  67         enum AVSampleFormat out_fmt = av_get_planar_sample_fmt(avr->out_sample_fmt);
  68         int max_bps = FFMAX(av_get_bytes_per_sample(in_fmt),
  69                             av_get_bytes_per_sample(out_fmt));
  70         if (max_bps <= 2) {
  71             avr->internal_sample_fmt = AV_SAMPLE_FMT_S16P;
  72         } else if (avr->mixing_needed) {
  73             avr->internal_sample_fmt = AV_SAMPLE_FMT_FLTP;
  74         } else {
  75             if (max_bps <= 4) {
  76                 if (in_fmt  == AV_SAMPLE_FMT_S32P ||
  77                     out_fmt == AV_SAMPLE_FMT_S32P) {
  78                     if (in_fmt  == AV_SAMPLE_FMT_FLTP ||
  79                         out_fmt == AV_SAMPLE_FMT_FLTP) {
  80                         /* if one is s32 and the other is flt, use dbl */
  81                         avr->internal_sample_fmt = AV_SAMPLE_FMT_DBLP;
  82                     } else {
  83                         /* if one is s32 and the other is s32, s16, or u8, use s32 */
  84                         avr->internal_sample_fmt = AV_SAMPLE_FMT_S32P;
  85                     }
  86                 } else {
  87                     /* if one is flt and the other is flt, s16 or u8, use flt */
  88                     avr->internal_sample_fmt = AV_SAMPLE_FMT_FLTP;
  89                 }
  90             } else {
  91                 /* if either is dbl, use dbl */
  92                 avr->internal_sample_fmt = AV_SAMPLE_FMT_DBLP;
  93             }
  94         }
  95         av_log(avr, AV_LOG_DEBUG, "Using %s as internal sample format\n",
  96                av_get_sample_fmt_name(avr->internal_sample_fmt));
  97     }
  98
  99     /* treat all mono as planar for easier comparison */
 100     if (avr->in_channels == 1)
 101         avr->in_sample_fmt = av_get_planar_sample_fmt(avr->in_sample_fmt);
 102     if (avr->out_channels == 1)
 103         avr->out_sample_fmt = av_get_planar_sample_fmt(avr->out_sample_fmt);
 104
 105     /* we may need to add an extra conversion in order to remap channels if
 106        the output format is not planar */
 107     if (avr->use_channel_map && !avr->mixing_needed && !avr->resample_needed &&
 108         !av_sample_fmt_is_planar(avr->out_sample_fmt)) {
 109         avr->internal_sample_fmt = av_get_planar_sample_fmt(avr->out_sample_fmt);
 110     }
 111
 112     /* set sample format conversion parameters */
 113     if (avr->resample_needed || avr->mixing_needed)
 114         avr->in_convert_needed = avr->in_sample_fmt != avr->internal_sample_fmt;
 115     else
 116         avr->in_convert_needed = avr->use_channel_map &&
 117                                  !av_sample_fmt_is_planar(avr->out_sample_fmt);
 118
 119     if (avr->resample_needed || avr->mixing_needed || avr->in_convert_needed)
 120         avr->out_convert_needed = avr->internal_sample_fmt != avr->out_sample_fmt;
 121     else
 122         avr->out_convert_needed = avr->in_sample_fmt != avr->out_sample_fmt;
 123
 124     avr->in_copy_needed = !avr->in_convert_needed && (avr->mixing_needed ||
 125                           (avr->use_channel_map && avr->resample_needed));
 126
 127     if (avr->use_channel_map) {
 128         if (avr->in_copy_needed) {
 129             avr->remap_point = REMAP_IN_COPY;
 130             av_dlog(avr, "remap channels during in_copy\n");
 131         } else if (avr->in_convert_needed) {
 132             avr->remap_point = REMAP_IN_CONVERT;
 133             av_dlog(avr, "remap channels during in_convert\n");
 134         } else if (avr->out_convert_needed) {
 135             avr->remap_point = REMAP_OUT_CONVERT;
 136             av_dlog(avr, "remap channels during out_convert\n");
 137         } else {
 138             avr->remap_point = REMAP_OUT_COPY;
 139             av_dlog(avr, "remap channels during out_copy\n");
 140         }
 141
 142 #ifdef DEBUG
 143         {
 144             int ch;
 145             av_dlog(avr, "output map: ");
 146             if (avr->ch_map_info.do_remap)
 147                 for (ch = 0; ch < avr->in_channels; ch++)
 148                     av_dlog(avr, " % 2d", avr->ch_map_info.channel_map[ch]);
 149             else
 150                 av_dlog(avr, "n/a");
 151             av_dlog(avr, "\n");
 152             av_dlog(avr, "copy map:   ");
 153             if (avr->ch_map_info.do_copy)
 154                 for (ch = 0; ch < avr->in_channels; ch++)
 155                     av_dlog(avr, " % 2d", avr->ch_map_info.channel_copy[ch]);
 156             else
 157                 av_dlog(avr, "n/a");
 158             av_dlog(avr, "\n");
 159             av_dlog(avr, "zero map:   ");
 160             if (avr->ch_map_info.do_zero)
 161                 for (ch = 0; ch < avr->in_channels; ch++)
 162                     av_dlog(avr, " % 2d", avr->ch_map_info.channel_zero[ch]);
 163             else
 164                 av_dlog(avr, "n/a");
 165             av_dlog(avr, "\n");
 166             av_dlog(avr, "input map:  ");
 167             for (ch = 0; ch < avr->in_channels; ch++)
 168                 av_dlog(avr, " % 2d", avr->ch_map_info.input_map[ch]);
 169             av_dlog(avr, "\n");
 170         }
 171 #endif
 172     } else
 173         avr->remap_point = REMAP_NONE;
 174
 175     /* allocate buffers */
 176     if (avr->in_copy_needed || avr->in_convert_needed) {
 177         avr->in_buffer = ff_audio_data_alloc(FFMAX(avr->in_channels, avr->out_channels),
 178                                              0, avr->internal_sample_fmt,
 179                                              "in_buffer");
 180         if (!avr->in_buffer) {
 181             ret = AVERROR(EINVAL);
 182             goto error;
 183         }
 184     }
 185     if (avr->resample_needed) {
 186         avr->resample_out_buffer = ff_audio_data_alloc(avr->out_channels,
 187                                                        0, avr->internal_sample_fmt,
 188                                                        "resample_out_buffer");
 189         if (!avr->resample_out_buffer) {
 190             ret = AVERROR(EINVAL);
 191             goto error;
 192         }
 193     }
 194     if (avr->out_convert_needed) {
 195         avr->out_buffer = ff_audio_data_alloc(avr->out_channels, 0,
 196                                               avr->out_sample_fmt, "out_buffer");
 197         if (!avr->out_buffer) {
 198             ret = AVERROR(EINVAL);
 199             goto error;
 200         }
 201     }
 202     avr->out_fifo = av_audio_fifo_alloc(avr->out_sample_fmt, avr->out_channels,
 203                                         1024);
 204     if (!avr->out_fifo) {
 205         ret = AVERROR(ENOMEM);
 206         goto error;
 207     }
 208
 209     /* setup contexts */
 210     if (avr->in_convert_needed) {
 211         avr->ac_in = ff_audio_convert_alloc(avr, avr->internal_sample_fmt,
 212                                             avr->in_sample_fmt, avr->in_channels,
 213                                             avr->in_sample_rate,
 214                                             avr->remap_point == REMAP_IN_CONVERT);
 215         if (!avr->ac_in) {
 216             ret = AVERROR(ENOMEM);
 217             goto error;
 218         }
 219     }
 220     if (avr->out_convert_needed) {
 221         enum AVSampleFormat src_fmt;
 222         if (avr->in_convert_needed)
 223             src_fmt = avr->internal_sample_fmt;
 224         else
 225             src_fmt = avr->in_sample_fmt;
 226         avr->ac_out = ff_audio_convert_alloc(avr, avr->out_sample_fmt, src_fmt,
 227                                              avr->out_channels,
 228                                              avr->out_sample_rate,
 229                                              avr->remap_point == REMAP_OUT_CONVERT);
 230         if (!avr->ac_out) {
 231             ret = AVERROR(ENOMEM);
 232             goto error;
 233         }
 234     }
 235     if (avr->resample_needed) {
 236         avr->resample = ff_audio_resample_init(avr);
 237         if (!avr->resample) {
 238             ret = AVERROR(ENOMEM);
 239             goto error;
 240         }
 241     }
 242     if (avr->mixing_needed) {
 243         avr->am = ff_audio_mix_alloc(avr);
 244         if (!avr->am) {
 245             ret = AVERROR(ENOMEM);
 246             goto error;
 247         }
 248     }
 249
 250     return 0;
 251
 252 error:
 253     avresample_close(avr);
 254     return ret;
 255 }
 256
 257 void avresample_close(AVAudioResampleContext *avr)
 258 {
 259     ff_audio_data_free(&avr->in_buffer);
 260     ff_audio_data_free(&avr->resample_out_buffer);
 261     ff_audio_data_free(&avr->out_buffer);
 262     av_audio_fifo_free(avr->out_fifo);
 263     avr->out_fifo = NULL;
 264     ff_audio_convert_free(&avr->ac_in);
 265     ff_audio_convert_free(&avr->ac_out);
 266     ff_audio_resample_free(&avr->resample);
 267     ff_audio_mix_free(&avr->am);
 268     av_freep(&avr->mix_matrix);
 269
 270     avr->use_channel_map = 0;
 271 }
 272
 273 void avresample_free(AVAudioResampleContext **avr)
 274 {
 275     if (!*avr)
 276         return;
 277     avresample_close(*avr);
 278     av_opt_free(*avr);
 279     av_freep(avr);
 280 }
 281
 282 static int handle_buffered_output(AVAudioResampleContext *avr,
 283                                   AudioData *output, AudioData *converted)
 284 {
 285     int ret;
 286
 287     if (!output || av_audio_fifo_size(avr->out_fifo) > 0 ||
 288         (converted && output->allocated_samples < converted->nb_samples)) {
 289         if (converted) {
 290             /* if there are any samples in the output FIFO or if the
 291                user-supplied output buffer is not large enough for all samples,
 292                we add to the output FIFO */
 293             av_dlog(avr, "[FIFO] add %s to out_fifo\n", converted->name);
 294             ret = ff_audio_data_add_to_fifo(avr->out_fifo, converted, 0,
 295                                             converted->nb_samples);
 296             if (ret < 0)
 297                 return ret;
 298         }
 299
 300         /* if the user specified an output buffer, read samples from the output
 301            FIFO to the user output */
 302         if (output && output->allocated_samples > 0) {
 303             av_dlog(avr, "[FIFO] read from out_fifo to output\n");
 304             av_dlog(avr, "[end conversion]\n");
 305             return ff_audio_data_read_from_fifo(avr->out_fifo, output,
 306                                                 output->allocated_samples);
 307         }
 308     } else if (converted) {
 309         /* copy directly to output if it is large enough or there is not any
 310            data in the output FIFO */
 311         av_dlog(avr, "[copy] %s to output\n", converted->name);
 312         output->nb_samples = 0;
 313         ret = ff_audio_data_copy(output, converted,
 314                                  avr->remap_point == REMAP_OUT_COPY ?
 315                                  &avr->ch_map_info : NULL);
 316         if (ret < 0)
 317             return ret;
 318         av_dlog(avr, "[end conversion]\n");
 319         return output->nb_samples;
 320     }
 321     av_dlog(avr, "[end conversion]\n");
 322     return 0;
 323 }
 324
 325 int attribute_align_arg avresample_convert(AVAudioResampleContext *avr,
 326                                            uint8_t **output, int out_plane_size,
 327                                            int out_samples, uint8_t **input,
 328                                            int in_plane_size, int in_samples)
 329 {
 330     AudioData input_buffer;
 331     AudioData output_buffer;
 332     AudioData *current_buffer;
 333     int ret, direct_output;
 334
 335     /* reset internal buffers */
 336     if (avr->in_buffer) {
 337         avr->in_buffer->nb_samples = 0;
 338         ff_audio_data_set_channels(avr->in_buffer,
 339                                    avr->in_buffer->allocated_channels);
 340     }
 341     if (avr->resample_out_buffer) {
 342         avr->resample_out_buffer->nb_samples = 0;
 343         ff_audio_data_set_channels(avr->resample_out_buffer,
 344                                    avr->resample_out_buffer->allocated_channels);
 345     }
 346     if (avr->out_buffer) {
 347         avr->out_buffer->nb_samples = 0;
 348         ff_audio_data_set_channels(avr->out_buffer,
 349                                    avr->out_buffer->allocated_channels);
 350     }
 351
 352     av_dlog(avr, "[start conversion]\n");
 353
 354     /* initialize output_buffer with output data */
 355     direct_output = output && av_audio_fifo_size(avr->out_fifo) == 0;
 356     if (output) {
 357         ret = ff_audio_data_init(&output_buffer, output, out_plane_size,
 358                                  avr->out_channels, out_samples,
 359                                  avr->out_sample_fmt, 0, "output");
 360         if (ret < 0)
 361             return ret;
 362         output_buffer.nb_samples = 0;
 363     }
 364
 365     if (input) {
 366         /* initialize input_buffer with input data */
 367         ret = ff_audio_data_init(&input_buffer, input, in_plane_size,
 368                                  avr->in_channels, in_samples,
 369                                  avr->in_sample_fmt, 1, "input");
 370         if (ret < 0)
 371             return ret;
 372         current_buffer = &input_buffer;
 373
 374         if (avr->upmix_needed && !avr->in_convert_needed && !avr->resample_needed &&
 375             !avr->out_convert_needed && direct_output && out_samples >= in_samples) {
 376             /* in some rare cases we can copy input to output and upmix
 377                directly in the output buffer */
 378             av_dlog(avr, "[copy] %s to output\n", current_buffer->name);
 379             ret = ff_audio_data_copy(&output_buffer, current_buffer,
 380                                      avr->remap_point == REMAP_OUT_COPY ?
 381                                      &avr->ch_map_info : NULL);
 382             if (ret < 0)
 383                 return ret;
 384             current_buffer = &output_buffer;
 385         } else if (avr->remap_point == REMAP_OUT_COPY &&
 386                    (!direct_output || out_samples < in_samples)) {
 387             /* if remapping channels during output copy, we may need to
 388              * use an intermediate buffer in order to remap before adding
 389              * samples to the output fifo */
 390             av_dlog(avr, "[copy] %s to out_buffer\n", current_buffer->name);
 391             ret = ff_audio_data_copy(avr->out_buffer, current_buffer,
 392                                      &avr->ch_map_info);
 393             if (ret < 0)
 394                 return ret;
 395             current_buffer = avr->out_buffer;
 396         } else if (avr->in_copy_needed || avr->in_convert_needed) {
 397             /* if needed, copy or convert input to in_buffer, and downmix if
 398                applicable */
 399             if (avr->in_convert_needed) {
 400                 ret = ff_audio_data_realloc(avr->in_buffer,
 401                                             current_buffer->nb_samples);
 402                 if (ret < 0)
 403                     return ret;
 404                 av_dlog(avr, "[convert] %s to in_buffer\n", current_buffer->name);
 405                 ret = ff_audio_convert(avr->ac_in, avr->in_buffer,
 406                                        current_buffer);
 407                 if (ret < 0)
 408                     return ret;
 409             } else {
 410                 av_dlog(avr, "[copy] %s to in_buffer\n", current_buffer->name);
 411                 ret = ff_audio_data_copy(avr->in_buffer, current_buffer,
 412                                          avr->remap_point == REMAP_IN_COPY ?
 413                                          &avr->ch_map_info : NULL);
 414                 if (ret < 0)
 415                     return ret;
 416             }
 417             ff_audio_data_set_channels(avr->in_buffer, avr->in_channels);
 418             if (avr->downmix_needed) {
 419                 av_dlog(avr, "[downmix] in_buffer\n");
 420                 ret = ff_audio_mix(avr->am, avr->in_buffer);
 421                 if (ret < 0)
 422                     return ret;
 423             }
 424             current_buffer = avr->in_buffer;
 425         }
 426     } else {
 427         /* flush resampling buffer and/or output FIFO if input is NULL */
 428         if (!avr->resample_needed)
 429             return handle_buffered_output(avr, output ? &output_buffer : NULL,
 430                                           NULL);
 431         current_buffer = NULL;
 432     }
 433
 434     if (avr->resample_needed) {
 435         AudioData *resample_out;
 436
 437         if (!avr->out_convert_needed && direct_output && out_samples > 0)
 438             resample_out = &output_buffer;
 439         else
 440             resample_out = avr->resample_out_buffer;
 441         av_dlog(avr, "[resample] %s to %s\n", current_buffer->name,
 442                 resample_out->name);
 443         ret = ff_audio_resample(avr->resample, resample_out,
 444                                 current_buffer);
 445         if (ret < 0)
 446             return ret;
 447
 448         /* if resampling did not produce any samples, just return 0 */
 449         if (resample_out->nb_samples == 0) {
 450             av_dlog(avr, "[end conversion]\n");
 451             return 0;
 452         }
 453
 454         current_buffer = resample_out;
 455     }
 456
 457     if (avr->upmix_needed) {
 458         av_dlog(avr, "[upmix] %s\n", current_buffer->name);
 459         ret = ff_audio_mix(avr->am, current_buffer);
 460         if (ret < 0)
 461             return ret;
 462     }
 463
 464     /* if we resampled or upmixed directly to output, return here */
 465     if (current_buffer == &output_buffer) {
 466         av_dlog(avr, "[end conversion]\n");
 467         return current_buffer->nb_samples;
 468     }
 469
 470     if (avr->out_convert_needed) {
 471         if (direct_output && out_samples >= current_buffer->nb_samples) {
 472             /* convert directly to output */
 473             av_dlog(avr, "[convert] %s to output\n", current_buffer->name);
 474             ret = ff_audio_convert(avr->ac_out, &output_buffer, current_buffer);
 475             if (ret < 0)
 476                 return ret;
 477
 478             av_dlog(avr, "[end conversion]\n");
 479             return output_buffer.nb_samples;
 480         } else {
 481             ret = ff_audio_data_realloc(avr->out_buffer,
 482                                         current_buffer->nb_samples);
 483             if (ret < 0)
 484                 return ret;
 485             av_dlog(avr, "[convert] %s to out_buffer\n", current_buffer->name);
 486             ret = ff_audio_convert(avr->ac_out, avr->out_buffer,
 487                                    current_buffer);
 488             if (ret < 0)
 489                 return ret;
 490             current_buffer = avr->out_buffer;
 491         }
 492     }
 493
 494     return handle_buffered_output(avr, output ? &output_buffer : NULL,
 495                                   current_buffer);
 496 }
 497
 498 int avresample_get_matrix(AVAudioResampleContext *avr, double *matrix,
 499                           int stride)
 500 {
 501     int in_channels, out_channels, i, o;
 502
 503     if (avr->am)
 504         return ff_audio_mix_get_matrix(avr->am, matrix, stride);
 505
 506     in_channels  = av_get_channel_layout_nb_channels(avr->in_channel_layout);
 507     out_channels = av_get_channel_layout_nb_channels(avr->out_channel_layout);
 508
 509     if ( in_channels <= 0 ||  in_channels > AVRESAMPLE_MAX_CHANNELS ||
 510         out_channels <= 0 || out_channels > AVRESAMPLE_MAX_CHANNELS) {
 511         av_log(avr, AV_LOG_ERROR, "Invalid channel layouts\n");
 512         return AVERROR(EINVAL);
 513     }
 514
 515     if (!avr->mix_matrix) {
 516         av_log(avr, AV_LOG_ERROR, "matrix is not set\n");
 517         return AVERROR(EINVAL);
 518     }
 519
 520     for (o = 0; o < out_channels; o++)
 521         for (i = 0; i < in_channels; i++)
 522             matrix[o * stride + i] = avr->mix_matrix[o * in_channels + i];
 523
 524     return 0;
 525 }
 526
 527 int avresample_set_matrix(AVAudioResampleContext *avr, const double *matrix,
 528                           int stride)
 529 {
 530     int in_channels, out_channels, i, o;
 531
 532     if (avr->am)
 533         return ff_audio_mix_set_matrix(avr->am, matrix, stride);
 534
 535     in_channels  = av_get_channel_layout_nb_channels(avr->in_channel_layout);
 536     out_channels = av_get_channel_layout_nb_channels(avr->out_channel_layout);
 537
 538     if ( in_channels <= 0 ||  in_channels > AVRESAMPLE_MAX_CHANNELS ||
 539         out_channels <= 0 || out_channels > AVRESAMPLE_MAX_CHANNELS) {
 540         av_log(avr, AV_LOG_ERROR, "Invalid channel layouts\n");
 541         return AVERROR(EINVAL);
 542     }
 543
 544     if (avr->mix_matrix)
 545         av_freep(&avr->mix_matrix);
 546     avr->mix_matrix = av_malloc(in_channels * out_channels *
 547                                 sizeof(*avr->mix_matrix));
 548     if (!avr->mix_matrix)
 549         return AVERROR(ENOMEM);
 550
 551     for (o = 0; o < out_channels; o++)
 552         for (i = 0; i < in_channels; i++)
 553             avr->mix_matrix[o * in_channels + i] = matrix[o * stride + i];
 554
 555     return 0;
 556 }
 557
 558 int avresample_set_channel_mapping(AVAudioResampleContext *avr,
 559                                    const int *channel_map)
 560 {
 561     ChannelMapInfo *info = &avr->ch_map_info;
 562     int in_channels, ch, i;
 563
 564     in_channels = av_get_channel_layout_nb_channels(avr->in_channel_layout);
 565     if (in_channels <= 0 ||  in_channels > AVRESAMPLE_MAX_CHANNELS) {
 566         av_log(avr, AV_LOG_ERROR, "Invalid input channel layout\n");
 567         return AVERROR(EINVAL);
 568     }
 569
 570     memset(info, 0, sizeof(*info));
 571     memset(info->input_map, -1, sizeof(info->input_map));
 572
 573     for (ch = 0; ch < in_channels; ch++) {
 574         if (channel_map[ch] >= in_channels) {
 575             av_log(avr, AV_LOG_ERROR, "Invalid channel map\n");
 576             return AVERROR(EINVAL);
 577         }
 578         if (channel_map[ch] < 0) {
 579             info->channel_zero[ch] =  1;
 580             info->channel_map[ch]  = -1;
 581             info->do_zero          =  1;
 582         } else if (info->input_map[channel_map[ch]] >= 0) {
 583             info->channel_copy[ch] = info->input_map[channel_map[ch]];
 584             info->channel_map[ch]  = -1;
 585             info->do_copy          =  1;
 586         } else {
 587             info->channel_map[ch]            = channel_map[ch];
 588             info->input_map[channel_map[ch]] = ch;
 589             info->do_remap                   =  1;
 590         }
 591     }
 592     /* Fill-in unmapped input channels with unmapped output channels.
 593        This is used when remapping during conversion from interleaved to
 594        planar format. */
 595     for (ch = 0, i = 0; ch < in_channels && i < in_channels; ch++, i++) {
 596         while (ch < in_channels && info->input_map[ch] >= 0)
 597             ch++;
 598         while (i < in_channels && info->channel_map[i] >= 0)
 599             i++;
 600         if (ch >= in_channels || i >= in_channels)
 601             break;
 602         info->input_map[ch] = i;
 603     }
 604
 605     avr->use_channel_map = 1;
 606     return 0;
 607 }
 608
 609 int avresample_available(AVAudioResampleContext *avr)
 610 {
 611     return av_audio_fifo_size(avr->out_fifo);
 612 }
 613
 614 int avresample_read(AVAudioResampleContext *avr, uint8_t **output, int nb_samples)
 615 {
 616     if (!output)
 617         return av_audio_fifo_drain(avr->out_fifo, nb_samples);
 618     return av_audio_fifo_read(avr->out_fifo, (void**)output, nb_samples);
 619 }
 620
 621 unsigned avresample_version(void)
 622 {
 623     return LIBAVRESAMPLE_VERSION_INT;
 624 }
 625
 626 const char *avresample_license(void)
 627 {
 628 #define LICENSE_PREFIX "libavresample license: "
 629     return LICENSE_PREFIX LIBAV_LICENSE + sizeof(LICENSE_PREFIX) - 1;
 630 }
 631
 632 const char *avresample_configuration(void)
 633 {
 634     return LIBAV_CONFIGURATION;
 635 }