• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
1 /*
2  * Opus decoder
3  * Copyright (c) 2012 Andrew D'Addesio
4  * Copyright (c) 2013-2014 Mozilla Corporation
5  *
6  * This file is part of FFmpeg.
7  *
8  * FFmpeg is free software; you can redistribute it and/or
9  * modify it under the terms of the GNU Lesser General Public
10  * License as published by the Free Software Foundation; either
11  * version 2.1 of the License, or (at your option) any later version.
12  *
13  * FFmpeg is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
16  * Lesser General Public License for more details.
17  *
18  * You should have received a copy of the GNU Lesser General Public
19  * License along with FFmpeg; if not, write to the Free Software
20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21  */
22 
23 /**
24  * @file
25  * Opus decoder
26  * @author Andrew D'Addesio, Anton Khirnov
27  *
28  * Codec homepage: http://opus-codec.org/
29  * Specification: http://tools.ietf.org/html/rfc6716
30  * Ogg Opus specification: https://tools.ietf.org/html/draft-ietf-codec-oggopus-03
31  *
32  * Ogg-contained .opus files can be produced with opus-tools:
33  * http://git.xiph.org/?p=opus-tools.git
34  */
35 
36 #include <stdint.h>
37 
38 #include "libavutil/attributes.h"
39 #include "libavutil/audio_fifo.h"
40 #include "libavutil/channel_layout.h"
41 #include "libavutil/opt.h"
42 
43 #include "libswresample/swresample.h"
44 
45 #include "avcodec.h"
46 #include "get_bits.h"
47 #include "internal.h"
48 #include "mathops.h"
49 #include "opus.h"
50 #include "opustab.h"
51 #include "opus_celt.h"
52 
53 static const uint16_t silk_frame_duration_ms[16] = {
54     10, 20, 40, 60,
55     10, 20, 40, 60,
56     10, 20, 40, 60,
57     10, 20,
58     10, 20,
59 };
60 
61 /* number of samples of silence to feed to the resampler
62  * at the beginning */
63 static const int silk_resample_delay[] = {
64     4, 8, 11, 11, 11
65 };
66 
get_silk_samplerate(int config)67 static int get_silk_samplerate(int config)
68 {
69     if (config < 4)
70         return 8000;
71     else if (config < 8)
72         return 12000;
73     return 16000;
74 }
75 
opus_fade(float * out,const float * in1,const float * in2,const float * window,int len)76 static void opus_fade(float *out,
77                       const float *in1, const float *in2,
78                       const float *window, int len)
79 {
80     int i;
81     for (i = 0; i < len; i++)
82         out[i] = in2[i] * window[i] + in1[i] * (1.0 - window[i]);
83 }
84 
opus_flush_resample(OpusStreamContext * s,int nb_samples)85 static int opus_flush_resample(OpusStreamContext *s, int nb_samples)
86 {
87     int celt_size = av_audio_fifo_size(s->celt_delay);
88     int ret, i;
89     ret = swr_convert(s->swr,
90                       (uint8_t**)s->cur_out, nb_samples,
91                       NULL, 0);
92     if (ret < 0)
93         return ret;
94     else if (ret != nb_samples) {
95         av_log(s->avctx, AV_LOG_ERROR, "Wrong number of flushed samples: %d\n",
96                ret);
97         return AVERROR_BUG;
98     }
99 
100     if (celt_size) {
101         if (celt_size != nb_samples) {
102             av_log(s->avctx, AV_LOG_ERROR, "Wrong number of CELT delay samples.\n");
103             return AVERROR_BUG;
104         }
105         av_audio_fifo_read(s->celt_delay, (void**)s->celt_output, nb_samples);
106         for (i = 0; i < s->output_channels; i++) {
107             s->fdsp->vector_fmac_scalar(s->cur_out[i],
108                                         s->celt_output[i], 1.0,
109                                         nb_samples);
110         }
111     }
112 
113     if (s->redundancy_idx) {
114         for (i = 0; i < s->output_channels; i++)
115             opus_fade(s->cur_out[i], s->cur_out[i],
116                       s->redundancy_output[i] + 120 + s->redundancy_idx,
117                       ff_celt_window2 + s->redundancy_idx, 120 - s->redundancy_idx);
118         s->redundancy_idx = 0;
119     }
120 
121     s->cur_out[0]         += nb_samples;
122     s->cur_out[1]         += nb_samples;
123     s->remaining_out_size -= nb_samples * sizeof(float);
124 
125     return 0;
126 }
127 
opus_init_resample(OpusStreamContext * s)128 static int opus_init_resample(OpusStreamContext *s)
129 {
130     static const float delay[16] = { 0.0 };
131     const uint8_t *delayptr[2] = { (uint8_t*)delay, (uint8_t*)delay };
132     int ret;
133 
134     av_opt_set_int(s->swr, "in_sample_rate", s->silk_samplerate, 0);
135     ret = swr_init(s->swr);
136     if (ret < 0) {
137         av_log(s->avctx, AV_LOG_ERROR, "Error opening the resampler.\n");
138         return ret;
139     }
140 
141     ret = swr_convert(s->swr,
142                       NULL, 0,
143                       delayptr, silk_resample_delay[s->packet.bandwidth]);
144     if (ret < 0) {
145         av_log(s->avctx, AV_LOG_ERROR,
146                "Error feeding initial silence to the resampler.\n");
147         return ret;
148     }
149 
150     return 0;
151 }
152 
opus_decode_redundancy(OpusStreamContext * s,const uint8_t * data,int size)153 static int opus_decode_redundancy(OpusStreamContext *s, const uint8_t *data, int size)
154 {
155     int ret = ff_opus_rc_dec_init(&s->redundancy_rc, data, size);
156     if (ret < 0)
157         goto fail;
158     ff_opus_rc_dec_raw_init(&s->redundancy_rc, data + size, size);
159 
160     ret = ff_celt_decode_frame(s->celt, &s->redundancy_rc,
161                                s->redundancy_output,
162                                s->packet.stereo + 1, 240,
163                                0, ff_celt_band_end[s->packet.bandwidth]);
164     if (ret < 0)
165         goto fail;
166 
167     return 0;
168 fail:
169     av_log(s->avctx, AV_LOG_ERROR, "Error decoding the redundancy frame.\n");
170     return ret;
171 }
172 
opus_decode_frame(OpusStreamContext * s,const uint8_t * data,int size)173 static int opus_decode_frame(OpusStreamContext *s, const uint8_t *data, int size)
174 {
175     int samples    = s->packet.frame_duration;
176     int redundancy = 0;
177     int redundancy_size, redundancy_pos;
178     int ret, i, consumed;
179     int delayed_samples = s->delayed_samples;
180 
181     ret = ff_opus_rc_dec_init(&s->rc, data, size);
182     if (ret < 0)
183         return ret;
184 
185     /* decode the silk frame */
186     if (s->packet.mode == OPUS_MODE_SILK || s->packet.mode == OPUS_MODE_HYBRID) {
187         if (!swr_is_initialized(s->swr)) {
188             ret = opus_init_resample(s);
189             if (ret < 0)
190                 return ret;
191         }
192 
193         samples = ff_silk_decode_superframe(s->silk, &s->rc, s->silk_output,
194                                             FFMIN(s->packet.bandwidth, OPUS_BANDWIDTH_WIDEBAND),
195                                             s->packet.stereo + 1,
196                                             silk_frame_duration_ms[s->packet.config]);
197         if (samples < 0) {
198             av_log(s->avctx, AV_LOG_ERROR, "Error decoding a SILK frame.\n");
199             return samples;
200         }
201         samples = swr_convert(s->swr,
202                               (uint8_t**)s->cur_out, s->packet.frame_duration,
203                               (const uint8_t**)s->silk_output, samples);
204         if (samples < 0) {
205             av_log(s->avctx, AV_LOG_ERROR, "Error resampling SILK data.\n");
206             return samples;
207         }
208         av_assert2((samples & 7) == 0);
209         s->delayed_samples += s->packet.frame_duration - samples;
210     } else
211         ff_silk_flush(s->silk);
212 
213     // decode redundancy information
214     consumed = opus_rc_tell(&s->rc);
215     if (s->packet.mode == OPUS_MODE_HYBRID && consumed + 37 <= size * 8)
216         redundancy = ff_opus_rc_dec_log(&s->rc, 12);
217     else if (s->packet.mode == OPUS_MODE_SILK && consumed + 17 <= size * 8)
218         redundancy = 1;
219 
220     if (redundancy) {
221         redundancy_pos = ff_opus_rc_dec_log(&s->rc, 1);
222 
223         if (s->packet.mode == OPUS_MODE_HYBRID)
224             redundancy_size = ff_opus_rc_dec_uint(&s->rc, 256) + 2;
225         else
226             redundancy_size = size - (consumed + 7) / 8;
227         size -= redundancy_size;
228         if (size < 0) {
229             av_log(s->avctx, AV_LOG_ERROR, "Invalid redundancy frame size.\n");
230             return AVERROR_INVALIDDATA;
231         }
232 
233         if (redundancy_pos) {
234             ret = opus_decode_redundancy(s, data + size, redundancy_size);
235             if (ret < 0)
236                 return ret;
237             ff_celt_flush(s->celt);
238         }
239     }
240 
241     /* decode the CELT frame */
242     if (s->packet.mode == OPUS_MODE_CELT || s->packet.mode == OPUS_MODE_HYBRID) {
243         float *out_tmp[2] = { s->cur_out[0], s->cur_out[1] };
244         float **dst = (s->packet.mode == OPUS_MODE_CELT) ?
245                       out_tmp : s->celt_output;
246         int celt_output_samples = samples;
247         int delay_samples = av_audio_fifo_size(s->celt_delay);
248 
249         if (delay_samples) {
250             if (s->packet.mode == OPUS_MODE_HYBRID) {
251                 av_audio_fifo_read(s->celt_delay, (void**)s->celt_output, delay_samples);
252 
253                 for (i = 0; i < s->output_channels; i++) {
254                     s->fdsp->vector_fmac_scalar(out_tmp[i], s->celt_output[i], 1.0,
255                                                 delay_samples);
256                     out_tmp[i] += delay_samples;
257                 }
258                 celt_output_samples -= delay_samples;
259             } else {
260                 av_log(s->avctx, AV_LOG_WARNING,
261                        "Spurious CELT delay samples present.\n");
262                 av_audio_fifo_drain(s->celt_delay, delay_samples);
263                 if (s->avctx->err_recognition & AV_EF_EXPLODE)
264                     return AVERROR_BUG;
265             }
266         }
267 
268         ff_opus_rc_dec_raw_init(&s->rc, data + size, size);
269 
270         ret = ff_celt_decode_frame(s->celt, &s->rc, dst,
271                                    s->packet.stereo + 1,
272                                    s->packet.frame_duration,
273                                    (s->packet.mode == OPUS_MODE_HYBRID) ? 17 : 0,
274                                    ff_celt_band_end[s->packet.bandwidth]);
275         if (ret < 0)
276             return ret;
277 
278         if (s->packet.mode == OPUS_MODE_HYBRID) {
279             int celt_delay = s->packet.frame_duration - celt_output_samples;
280             void *delaybuf[2] = { s->celt_output[0] + celt_output_samples,
281                                   s->celt_output[1] + celt_output_samples };
282 
283             for (i = 0; i < s->output_channels; i++) {
284                 s->fdsp->vector_fmac_scalar(out_tmp[i],
285                                             s->celt_output[i], 1.0,
286                                             celt_output_samples);
287             }
288 
289             ret = av_audio_fifo_write(s->celt_delay, delaybuf, celt_delay);
290             if (ret < 0)
291                 return ret;
292         }
293     } else
294         ff_celt_flush(s->celt);
295 
296     if (s->redundancy_idx) {
297         for (i = 0; i < s->output_channels; i++)
298             opus_fade(s->cur_out[i], s->cur_out[i],
299                       s->redundancy_output[i] + 120 + s->redundancy_idx,
300                       ff_celt_window2 + s->redundancy_idx, 120 - s->redundancy_idx);
301         s->redundancy_idx = 0;
302     }
303     if (redundancy) {
304         if (!redundancy_pos) {
305             ff_celt_flush(s->celt);
306             ret = opus_decode_redundancy(s, data + size, redundancy_size);
307             if (ret < 0)
308                 return ret;
309 
310             for (i = 0; i < s->output_channels; i++) {
311                 opus_fade(s->cur_out[i] + samples - 120 + delayed_samples,
312                           s->cur_out[i] + samples - 120 + delayed_samples,
313                           s->redundancy_output[i] + 120,
314                           ff_celt_window2, 120 - delayed_samples);
315                 if (delayed_samples)
316                     s->redundancy_idx = 120 - delayed_samples;
317             }
318         } else {
319             for (i = 0; i < s->output_channels; i++) {
320                 memcpy(s->cur_out[i] + delayed_samples, s->redundancy_output[i], 120 * sizeof(float));
321                 opus_fade(s->cur_out[i] + 120 + delayed_samples,
322                           s->redundancy_output[i] + 120,
323                           s->cur_out[i] + 120 + delayed_samples,
324                           ff_celt_window2, 120);
325             }
326         }
327     }
328 
329     return samples;
330 }
331 
opus_decode_subpacket(OpusStreamContext * s,const uint8_t * buf,int buf_size,int nb_samples)332 static int opus_decode_subpacket(OpusStreamContext *s,
333                                  const uint8_t *buf, int buf_size,
334                                  int nb_samples)
335 {
336     int output_samples = 0;
337     int flush_needed   = 0;
338     int i, j, ret;
339 
340     s->cur_out[0]         = s->out[0];
341     s->cur_out[1]         = s->out[1];
342     s->remaining_out_size = s->out_size;
343 
344     /* check if we need to flush the resampler */
345     if (swr_is_initialized(s->swr)) {
346         if (buf) {
347             int64_t cur_samplerate;
348             av_opt_get_int(s->swr, "in_sample_rate", 0, &cur_samplerate);
349             flush_needed = (s->packet.mode == OPUS_MODE_CELT) || (cur_samplerate != s->silk_samplerate);
350         } else {
351             flush_needed = !!s->delayed_samples;
352         }
353     }
354 
355     if (!buf && !flush_needed)
356         return 0;
357 
358     /* use dummy output buffers if the channel is not mapped to anything */
359     if (!s->cur_out[0] ||
360         (s->output_channels == 2 && !s->cur_out[1])) {
361         av_fast_malloc(&s->out_dummy, &s->out_dummy_allocated_size,
362                        s->remaining_out_size);
363         if (!s->out_dummy)
364             return AVERROR(ENOMEM);
365         if (!s->cur_out[0])
366             s->cur_out[0] = s->out_dummy;
367         if (!s->cur_out[1])
368             s->cur_out[1] = s->out_dummy;
369     }
370 
371     /* flush the resampler if necessary */
372     if (flush_needed) {
373         ret = opus_flush_resample(s, s->delayed_samples);
374         if (ret < 0) {
375             av_log(s->avctx, AV_LOG_ERROR, "Error flushing the resampler.\n");
376             return ret;
377         }
378         swr_close(s->swr);
379         output_samples += s->delayed_samples;
380         s->delayed_samples = 0;
381 
382         if (!buf)
383             goto finish;
384     }
385 
386     /* decode all the frames in the packet */
387     for (i = 0; i < s->packet.frame_count; i++) {
388         int size = s->packet.frame_size[i];
389         int samples = opus_decode_frame(s, buf + s->packet.frame_offset[i], size);
390 
391         if (samples < 0) {
392             av_log(s->avctx, AV_LOG_ERROR, "Error decoding an Opus frame.\n");
393             if (s->avctx->err_recognition & AV_EF_EXPLODE)
394                 return samples;
395 
396             for (j = 0; j < s->output_channels; j++)
397                 memset(s->cur_out[j], 0, s->packet.frame_duration * sizeof(float));
398             samples = s->packet.frame_duration;
399         }
400         output_samples += samples;
401 
402         for (j = 0; j < s->output_channels; j++)
403             s->cur_out[j] += samples;
404         s->remaining_out_size -= samples * sizeof(float);
405     }
406 
407 finish:
408     s->cur_out[0] = s->cur_out[1] = NULL;
409     s->remaining_out_size = 0;
410 
411     return output_samples;
412 }
413 
opus_decode_packet(AVCodecContext * avctx,void * data,int * got_frame_ptr,AVPacket * avpkt)414 static int opus_decode_packet(AVCodecContext *avctx, void *data,
415                               int *got_frame_ptr, AVPacket *avpkt)
416 {
417     OpusContext *c      = avctx->priv_data;
418     AVFrame *frame      = data;
419     const uint8_t *buf  = avpkt->data;
420     int buf_size        = avpkt->size;
421     int coded_samples   = 0;
422     int decoded_samples = INT_MAX;
423     int delayed_samples = 0;
424     int i, ret;
425 
426     /* calculate the number of delayed samples */
427     for (i = 0; i < c->nb_streams; i++) {
428         OpusStreamContext *s = &c->streams[i];
429         s->out[0] =
430         s->out[1] = NULL;
431         delayed_samples = FFMAX(delayed_samples,
432                                 s->delayed_samples + av_audio_fifo_size(s->sync_buffer));
433     }
434 
435     /* decode the header of the first sub-packet to find out the sample count */
436     if (buf) {
437         OpusPacket *pkt = &c->streams[0].packet;
438         ret = ff_opus_parse_packet(pkt, buf, buf_size, c->nb_streams > 1);
439         if (ret < 0) {
440             av_log(avctx, AV_LOG_ERROR, "Error parsing the packet header.\n");
441             return ret;
442         }
443         coded_samples += pkt->frame_count * pkt->frame_duration;
444         c->streams[0].silk_samplerate = get_silk_samplerate(pkt->config);
445     }
446 
447     frame->nb_samples = coded_samples + delayed_samples;
448 
449     /* no input or buffered data => nothing to do */
450     if (!frame->nb_samples) {
451         *got_frame_ptr = 0;
452         return 0;
453     }
454 
455     /* setup the data buffers */
456     ret = ff_get_buffer(avctx, frame, 0);
457     if (ret < 0)
458         return ret;
459     frame->nb_samples = 0;
460 
461     for (i = 0; i < avctx->channels; i++) {
462         ChannelMap *map = &c->channel_maps[i];
463         if (!map->copy)
464             c->streams[map->stream_idx].out[map->channel_idx] = (float*)frame->extended_data[i];
465     }
466 
467     /* read the data from the sync buffers */
468     for (i = 0; i < c->nb_streams; i++) {
469         OpusStreamContext *s = &c->streams[i];
470         float          **out = s->out;
471         int sync_size = av_audio_fifo_size(s->sync_buffer);
472 
473         float sync_dummy[32];
474         int out_dummy = (!out[0]) | ((!out[1]) << 1);
475 
476         if (!out[0])
477             out[0] = sync_dummy;
478         if (!out[1])
479             out[1] = sync_dummy;
480         if (out_dummy && sync_size > FF_ARRAY_ELEMS(sync_dummy))
481             return AVERROR_BUG;
482 
483         ret = av_audio_fifo_read(s->sync_buffer, (void**)out, sync_size);
484         if (ret < 0)
485             return ret;
486 
487         if (out_dummy & 1)
488             out[0] = NULL;
489         else
490             out[0] += ret;
491         if (out_dummy & 2)
492             out[1] = NULL;
493         else
494             out[1] += ret;
495 
496         s->out_size = frame->linesize[0] - ret * sizeof(float);
497     }
498 
499     /* decode each sub-packet */
500     for (i = 0; i < c->nb_streams; i++) {
501         OpusStreamContext *s = &c->streams[i];
502 
503         if (i && buf) {
504             ret = ff_opus_parse_packet(&s->packet, buf, buf_size, i != c->nb_streams - 1);
505             if (ret < 0) {
506                 av_log(avctx, AV_LOG_ERROR, "Error parsing the packet header.\n");
507                 return ret;
508             }
509             if (coded_samples != s->packet.frame_count * s->packet.frame_duration) {
510                 av_log(avctx, AV_LOG_ERROR,
511                        "Mismatching coded sample count in substream %d.\n", i);
512                 return AVERROR_INVALIDDATA;
513             }
514 
515             s->silk_samplerate = get_silk_samplerate(s->packet.config);
516         }
517 
518         ret = opus_decode_subpacket(&c->streams[i], buf, s->packet.data_size,
519                                     coded_samples);
520         if (ret < 0)
521             return ret;
522         s->decoded_samples = ret;
523         decoded_samples       = FFMIN(decoded_samples, ret);
524 
525         buf      += s->packet.packet_size;
526         buf_size -= s->packet.packet_size;
527     }
528 
529     /* buffer the extra samples */
530     for (i = 0; i < c->nb_streams; i++) {
531         OpusStreamContext *s = &c->streams[i];
532         int   buffer_samples = s->decoded_samples - decoded_samples;
533         if (buffer_samples) {
534             float *buf[2] = { s->out[0] ? s->out[0] : (float*)frame->extended_data[0],
535                               s->out[1] ? s->out[1] : (float*)frame->extended_data[0] };
536             buf[0] += decoded_samples;
537             buf[1] += decoded_samples;
538             ret = av_audio_fifo_write(s->sync_buffer, (void**)buf, buffer_samples);
539             if (ret < 0)
540                 return ret;
541         }
542     }
543 
544     for (i = 0; i < avctx->channels; i++) {
545         ChannelMap *map = &c->channel_maps[i];
546 
547         /* handle copied channels */
548         if (map->copy) {
549             memcpy(frame->extended_data[i],
550                    frame->extended_data[map->copy_idx],
551                    frame->linesize[0]);
552         } else if (map->silence) {
553             memset(frame->extended_data[i], 0, frame->linesize[0]);
554         }
555 
556         if (c->gain_i && decoded_samples > 0) {
557             c->fdsp->vector_fmul_scalar((float*)frame->extended_data[i],
558                                        (float*)frame->extended_data[i],
559                                        c->gain, FFALIGN(decoded_samples, 8));
560         }
561     }
562 
563     frame->nb_samples = decoded_samples;
564     *got_frame_ptr    = !!decoded_samples;
565 
566     return avpkt->size;
567 }
568 
opus_decode_flush(AVCodecContext * ctx)569 static av_cold void opus_decode_flush(AVCodecContext *ctx)
570 {
571     OpusContext *c = ctx->priv_data;
572     int i;
573 
574     for (i = 0; i < c->nb_streams; i++) {
575         OpusStreamContext *s = &c->streams[i];
576 
577         memset(&s->packet, 0, sizeof(s->packet));
578         s->delayed_samples = 0;
579 
580         av_audio_fifo_drain(s->celt_delay, av_audio_fifo_size(s->celt_delay));
581         swr_close(s->swr);
582 
583         av_audio_fifo_drain(s->sync_buffer, av_audio_fifo_size(s->sync_buffer));
584 
585         ff_silk_flush(s->silk);
586         ff_celt_flush(s->celt);
587     }
588 }
589 
opus_decode_close(AVCodecContext * avctx)590 static av_cold int opus_decode_close(AVCodecContext *avctx)
591 {
592     OpusContext *c = avctx->priv_data;
593     int i;
594 
595     for (i = 0; i < c->nb_streams; i++) {
596         OpusStreamContext *s = &c->streams[i];
597 
598         ff_silk_free(&s->silk);
599         ff_celt_free(&s->celt);
600 
601         av_freep(&s->out_dummy);
602         s->out_dummy_allocated_size = 0;
603 
604         av_audio_fifo_free(s->sync_buffer);
605         av_audio_fifo_free(s->celt_delay);
606         swr_free(&s->swr);
607     }
608 
609     av_freep(&c->streams);
610 
611     c->nb_streams = 0;
612 
613     av_freep(&c->channel_maps);
614     av_freep(&c->fdsp);
615 
616     return 0;
617 }
618 
opus_decode_init(AVCodecContext * avctx)619 static av_cold int opus_decode_init(AVCodecContext *avctx)
620 {
621     OpusContext *c = avctx->priv_data;
622     int ret, i, j;
623 
624     avctx->sample_fmt  = AV_SAMPLE_FMT_FLTP;
625     avctx->sample_rate = 48000;
626 
627     c->fdsp = avpriv_float_dsp_alloc(0);
628     if (!c->fdsp)
629         return AVERROR(ENOMEM);
630 
631     /* find out the channel configuration */
632     ret = ff_opus_parse_extradata(avctx, c);
633     if (ret < 0)
634         return ret;
635 
636     /* allocate and init each independent decoder */
637     c->streams = av_mallocz_array(c->nb_streams, sizeof(*c->streams));
638     if (!c->streams) {
639         c->nb_streams = 0;
640         return AVERROR(ENOMEM);
641     }
642 
643     for (i = 0; i < c->nb_streams; i++) {
644         OpusStreamContext *s = &c->streams[i];
645         uint64_t layout;
646 
647         s->output_channels = (i < c->nb_stereo_streams) ? 2 : 1;
648 
649         s->avctx = avctx;
650 
651         for (j = 0; j < s->output_channels; j++) {
652             s->silk_output[j]       = s->silk_buf[j];
653             s->celt_output[j]       = s->celt_buf[j];
654             s->redundancy_output[j] = s->redundancy_buf[j];
655         }
656 
657         s->fdsp = c->fdsp;
658 
659         s->swr =swr_alloc();
660         if (!s->swr)
661             return AVERROR(ENOMEM);
662 
663         layout = (s->output_channels == 1) ? AV_CH_LAYOUT_MONO : AV_CH_LAYOUT_STEREO;
664         av_opt_set_int(s->swr, "in_sample_fmt",      avctx->sample_fmt,  0);
665         av_opt_set_int(s->swr, "out_sample_fmt",     avctx->sample_fmt,  0);
666         av_opt_set_int(s->swr, "in_channel_layout",  layout,             0);
667         av_opt_set_int(s->swr, "out_channel_layout", layout,             0);
668         av_opt_set_int(s->swr, "out_sample_rate",    avctx->sample_rate, 0);
669         av_opt_set_int(s->swr, "filter_size",        16,                 0);
670 
671         ret = ff_silk_init(avctx, &s->silk, s->output_channels);
672         if (ret < 0)
673             return ret;
674 
675         ret = ff_celt_init(avctx, &s->celt, s->output_channels, c->apply_phase_inv);
676         if (ret < 0)
677             return ret;
678 
679         s->celt_delay = av_audio_fifo_alloc(avctx->sample_fmt,
680                                             s->output_channels, 1024);
681         if (!s->celt_delay)
682             return AVERROR(ENOMEM);
683 
684         s->sync_buffer = av_audio_fifo_alloc(avctx->sample_fmt,
685                                              s->output_channels, 32);
686         if (!s->sync_buffer)
687             return AVERROR(ENOMEM);
688     }
689 
690     return 0;
691 }
692 
693 #define OFFSET(x) offsetof(OpusContext, x)
694 #define AD AV_OPT_FLAG_AUDIO_PARAM | AV_OPT_FLAG_DECODING_PARAM
695 static const AVOption opus_options[] = {
696     { "apply_phase_inv", "Apply intensity stereo phase inversion", OFFSET(apply_phase_inv), AV_OPT_TYPE_BOOL, { .i64 = 1 }, 0, 1, AD },
697     { NULL },
698 };
699 
700 static const AVClass opus_class = {
701     .class_name = "Opus Decoder",
702     .item_name  = av_default_item_name,
703     .option     = opus_options,
704     .version    = LIBAVUTIL_VERSION_INT,
705 };
706 
707 AVCodec ff_opus_decoder = {
708     .name            = "opus",
709     .long_name       = NULL_IF_CONFIG_SMALL("Opus"),
710     .priv_class      = &opus_class,
711     .type            = AVMEDIA_TYPE_AUDIO,
712     .id              = AV_CODEC_ID_OPUS,
713     .priv_data_size  = sizeof(OpusContext),
714     .init            = opus_decode_init,
715     .close           = opus_decode_close,
716     .decode          = opus_decode_packet,
717     .flush           = opus_decode_flush,
718     .capabilities    = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_DELAY | AV_CODEC_CAP_CHANNEL_CONF,
719     .caps_internal   = FF_CODEC_CAP_INIT_THREADSAFE | FF_CODEC_CAP_INIT_CLEANUP,
720 };
721