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1 /*
2  * Opus encoder using libopus
3  * Copyright (c) 2012 Nathan Caldwell
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  */
21 
22 #include <opus.h>
23 #include <opus_multistream.h>
24 
25 #include "libavutil/opt.h"
26 #include "avcodec.h"
27 #include "bytestream.h"
28 #include "internal.h"
29 #include "libopus.h"
30 #include "vorbis.h"
31 #include "audio_frame_queue.h"
32 
33 typedef struct LibopusEncOpts {
34     int vbr;
35     int application;
36     int packet_loss;
37     int fec;
38     int complexity;
39     float frame_duration;
40     int packet_size;
41     int max_bandwidth;
42     int mapping_family;
43 #ifdef OPUS_SET_PHASE_INVERSION_DISABLED_REQUEST
44     int apply_phase_inv;
45 #endif
46 } LibopusEncOpts;
47 
48 typedef struct LibopusEncContext {
49     AVClass *class;
50     OpusMSEncoder *enc;
51     int stream_count;
52     uint8_t *samples;
53     LibopusEncOpts opts;
54     AudioFrameQueue afq;
55     const uint8_t *encoder_channel_map;
56 } LibopusEncContext;
57 
58 static const uint8_t opus_coupled_streams[8] = {
59     0, 1, 1, 2, 2, 2, 2, 3
60 };
61 
62 /* Opus internal to Vorbis channel order mapping written in the header */
63 static const uint8_t opus_vorbis_channel_map[8][8] = {
64     { 0 },
65     { 0, 1 },
66     { 0, 2, 1 },
67     { 0, 1, 2, 3 },
68     { 0, 4, 1, 2, 3 },
69     { 0, 4, 1, 2, 3, 5 },
70     { 0, 4, 1, 2, 3, 5, 6 },
71     { 0, 6, 1, 2, 3, 4, 5, 7 },
72 };
73 
74 /* libavcodec to libopus channel order mapping, passed to libopus */
75 static const uint8_t libavcodec_libopus_channel_map[8][8] = {
76     { 0 },
77     { 0, 1 },
78     { 0, 1, 2 },
79     { 0, 1, 2, 3 },
80     { 0, 1, 3, 4, 2 },
81     { 0, 1, 4, 5, 2, 3 },
82     { 0, 1, 5, 6, 2, 4, 3 },
83     { 0, 1, 6, 7, 4, 5, 2, 3 },
84 };
85 
libopus_write_header(AVCodecContext * avctx,int stream_count,int coupled_stream_count,int mapping_family,const uint8_t * channel_mapping)86 static void libopus_write_header(AVCodecContext *avctx, int stream_count,
87                                  int coupled_stream_count,
88                                  int mapping_family,
89                                  const uint8_t *channel_mapping)
90 {
91     uint8_t *p   = avctx->extradata;
92     int channels = avctx->channels;
93 
94     bytestream_put_buffer(&p, "OpusHead", 8);
95     bytestream_put_byte(&p, 1); /* Version */
96     bytestream_put_byte(&p, channels);
97     bytestream_put_le16(&p, avctx->initial_padding * 48000 / avctx->sample_rate); /* Lookahead samples at 48kHz */
98     bytestream_put_le32(&p, avctx->sample_rate); /* Original sample rate */
99     bytestream_put_le16(&p, 0); /* Gain of 0dB is recommended. */
100 
101     /* Channel mapping */
102     bytestream_put_byte(&p, mapping_family);
103     if (mapping_family != 0) {
104         bytestream_put_byte(&p, stream_count);
105         bytestream_put_byte(&p, coupled_stream_count);
106         bytestream_put_buffer(&p, channel_mapping, channels);
107     }
108 }
109 
libopus_configure_encoder(AVCodecContext * avctx,OpusMSEncoder * enc,LibopusEncOpts * opts)110 static int libopus_configure_encoder(AVCodecContext *avctx, OpusMSEncoder *enc,
111                                      LibopusEncOpts *opts)
112 {
113     int ret;
114 
115     if (avctx->global_quality) {
116         av_log(avctx, AV_LOG_ERROR,
117                "Quality-based encoding not supported, "
118                "please specify a bitrate and VBR setting.\n");
119         return AVERROR(EINVAL);
120     }
121 
122     ret = opus_multistream_encoder_ctl(enc, OPUS_SET_BITRATE(avctx->bit_rate));
123     if (ret != OPUS_OK) {
124         av_log(avctx, AV_LOG_ERROR,
125                "Failed to set bitrate: %s\n", opus_strerror(ret));
126         return ret;
127     }
128 
129     ret = opus_multistream_encoder_ctl(enc,
130                                        OPUS_SET_COMPLEXITY(opts->complexity));
131     if (ret != OPUS_OK)
132         av_log(avctx, AV_LOG_WARNING,
133                "Unable to set complexity: %s\n", opus_strerror(ret));
134 
135     ret = opus_multistream_encoder_ctl(enc, OPUS_SET_VBR(!!opts->vbr));
136     if (ret != OPUS_OK)
137         av_log(avctx, AV_LOG_WARNING,
138                "Unable to set VBR: %s\n", opus_strerror(ret));
139 
140     ret = opus_multistream_encoder_ctl(enc,
141                                        OPUS_SET_VBR_CONSTRAINT(opts->vbr == 2));
142     if (ret != OPUS_OK)
143         av_log(avctx, AV_LOG_WARNING,
144                "Unable to set constrained VBR: %s\n", opus_strerror(ret));
145 
146     ret = opus_multistream_encoder_ctl(enc,
147                                        OPUS_SET_PACKET_LOSS_PERC(opts->packet_loss));
148     if (ret != OPUS_OK)
149         av_log(avctx, AV_LOG_WARNING,
150                "Unable to set expected packet loss percentage: %s\n",
151                opus_strerror(ret));
152 
153     ret = opus_multistream_encoder_ctl(enc,
154                                        OPUS_SET_INBAND_FEC(opts->fec));
155     if (ret != OPUS_OK)
156         av_log(avctx, AV_LOG_WARNING,
157                "Unable to set inband FEC: %s\n",
158                opus_strerror(ret));
159 
160     if (avctx->cutoff) {
161         ret = opus_multistream_encoder_ctl(enc,
162                                            OPUS_SET_MAX_BANDWIDTH(opts->max_bandwidth));
163         if (ret != OPUS_OK)
164             av_log(avctx, AV_LOG_WARNING,
165                    "Unable to set maximum bandwidth: %s\n", opus_strerror(ret));
166     }
167 
168 #ifdef OPUS_SET_PHASE_INVERSION_DISABLED_REQUEST
169     ret = opus_multistream_encoder_ctl(enc,
170                                        OPUS_SET_PHASE_INVERSION_DISABLED(!opts->apply_phase_inv));
171     if (ret != OPUS_OK)
172         av_log(avctx, AV_LOG_WARNING,
173                "Unable to set phase inversion: %s\n",
174                opus_strerror(ret));
175 #endif
176     return OPUS_OK;
177 }
178 
libopus_check_max_channels(AVCodecContext * avctx,int max_channels)179 static int libopus_check_max_channels(AVCodecContext *avctx,
180                                       int max_channels) {
181     if (avctx->channels > max_channels) {
182         av_log(avctx, AV_LOG_ERROR, "Opus mapping family undefined for %d channels.\n",
183                avctx->channels);
184         return AVERROR(EINVAL);
185     }
186 
187     return 0;
188 }
189 
libopus_check_vorbis_layout(AVCodecContext * avctx,int mapping_family)190 static int libopus_check_vorbis_layout(AVCodecContext *avctx, int mapping_family) {
191     av_assert2(avctx->channels < FF_ARRAY_ELEMS(ff_vorbis_channel_layouts));
192 
193     if (!avctx->channel_layout) {
194         av_log(avctx, AV_LOG_WARNING,
195                "No channel layout specified. Opus encoder will use Vorbis "
196                "channel layout for %d channels.\n", avctx->channels);
197     } else if (avctx->channel_layout != ff_vorbis_channel_layouts[avctx->channels - 1]) {
198         char name[32];
199         av_get_channel_layout_string(name, sizeof(name), avctx->channels,
200                                      avctx->channel_layout);
201         av_log(avctx, AV_LOG_ERROR,
202                "Invalid channel layout %s for specified mapping family %d.\n",
203                name, mapping_family);
204 
205         return AVERROR(EINVAL);
206     }
207 
208     return 0;
209 }
210 
libopus_validate_layout_and_get_channel_map(AVCodecContext * avctx,int mapping_family,const uint8_t ** channel_map_result)211 static int libopus_validate_layout_and_get_channel_map(
212         AVCodecContext *avctx,
213         int mapping_family,
214         const uint8_t ** channel_map_result)
215 {
216     const uint8_t * channel_map = NULL;
217     int ret;
218 
219     switch (mapping_family) {
220     case -1:
221         ret = libopus_check_max_channels(avctx, 8);
222         if (ret == 0) {
223             ret = libopus_check_vorbis_layout(avctx, mapping_family);
224             /* Channels do not need to be reordered. */
225         }
226 
227         break;
228     case 0:
229         ret = libopus_check_max_channels(avctx, 2);
230         if (ret == 0) {
231             ret = libopus_check_vorbis_layout(avctx, mapping_family);
232         }
233         break;
234     case 1:
235         /* Opus expects channels to be in Vorbis order. */
236         ret = libopus_check_max_channels(avctx, 8);
237         if (ret == 0) {
238             ret = libopus_check_vorbis_layout(avctx, mapping_family);
239             channel_map = ff_vorbis_channel_layout_offsets[avctx->channels - 1];
240         }
241         break;
242     case 255:
243         ret = libopus_check_max_channels(avctx, 254);
244         break;
245     default:
246         av_log(avctx, AV_LOG_WARNING,
247                "Unknown channel mapping family %d. Output channel layout may be invalid.\n",
248                mapping_family);
249         ret = 0;
250     }
251 
252     *channel_map_result = channel_map;
253     return ret;
254 }
255 
libopus_encode_init(AVCodecContext * avctx)256 static av_cold int libopus_encode_init(AVCodecContext *avctx)
257 {
258     LibopusEncContext *opus = avctx->priv_data;
259     OpusMSEncoder *enc;
260     uint8_t libopus_channel_mapping[255];
261     int ret = OPUS_OK;
262     int av_ret;
263     int coupled_stream_count, header_size, frame_size;
264     int mapping_family;
265 
266     frame_size = opus->opts.frame_duration * 48000 / 1000;
267     switch (frame_size) {
268     case 120:
269     case 240:
270         if (opus->opts.application != OPUS_APPLICATION_RESTRICTED_LOWDELAY)
271             av_log(avctx, AV_LOG_WARNING,
272                    "LPC mode cannot be used with a frame duration of less "
273                    "than 10ms. Enabling restricted low-delay mode.\n"
274                    "Use a longer frame duration if this is not what you want.\n");
275         /* Frame sizes less than 10 ms can only use MDCT mode, so switching to
276          * RESTRICTED_LOWDELAY avoids an unnecessary extra 2.5ms lookahead. */
277         opus->opts.application = OPUS_APPLICATION_RESTRICTED_LOWDELAY;
278     case 480:
279     case 960:
280     case 1920:
281     case 2880:
282 #ifdef OPUS_FRAMESIZE_120_MS
283     case 3840:
284     case 4800:
285     case 5760:
286 #endif
287         opus->opts.packet_size =
288         avctx->frame_size      = frame_size * avctx->sample_rate / 48000;
289         break;
290     default:
291         av_log(avctx, AV_LOG_ERROR, "Invalid frame duration: %g.\n"
292                "Frame duration must be exactly one of: 2.5, 5, 10, 20, 40"
293 #ifdef OPUS_FRAMESIZE_120_MS
294                ", 60, 80, 100 or 120.\n",
295 #else
296                " or 60.\n",
297 #endif
298                opus->opts.frame_duration);
299         return AVERROR(EINVAL);
300     }
301 
302     if (avctx->compression_level < 0 || avctx->compression_level > 10) {
303         av_log(avctx, AV_LOG_WARNING,
304                "Compression level must be in the range 0 to 10. "
305                "Defaulting to 10.\n");
306         opus->opts.complexity = 10;
307     } else {
308         opus->opts.complexity = avctx->compression_level;
309     }
310 
311     if (avctx->cutoff) {
312         switch (avctx->cutoff) {
313         case  4000:
314             opus->opts.max_bandwidth = OPUS_BANDWIDTH_NARROWBAND;
315             break;
316         case  6000:
317             opus->opts.max_bandwidth = OPUS_BANDWIDTH_MEDIUMBAND;
318             break;
319         case  8000:
320             opus->opts.max_bandwidth = OPUS_BANDWIDTH_WIDEBAND;
321             break;
322         case 12000:
323             opus->opts.max_bandwidth = OPUS_BANDWIDTH_SUPERWIDEBAND;
324             break;
325         case 20000:
326             opus->opts.max_bandwidth = OPUS_BANDWIDTH_FULLBAND;
327             break;
328         default:
329             av_log(avctx, AV_LOG_WARNING,
330                    "Invalid frequency cutoff: %d. Using default maximum bandwidth.\n"
331                    "Cutoff frequency must be exactly one of: 4000, 6000, 8000, 12000 or 20000.\n",
332                    avctx->cutoff);
333             avctx->cutoff = 0;
334         }
335     }
336 
337     /* Channels may need to be reordered to match opus mapping. */
338     av_ret = libopus_validate_layout_and_get_channel_map(avctx, opus->opts.mapping_family,
339                                                          &opus->encoder_channel_map);
340     if (av_ret) {
341         return av_ret;
342     }
343 
344     if (opus->opts.mapping_family == -1) {
345         /* By default, use mapping family 1 for the header but use the older
346          * libopus multistream API to avoid surround masking. */
347 
348         /* Set the mapping family so that the value is correct in the header */
349         mapping_family = avctx->channels > 2 ? 1 : 0;
350         coupled_stream_count = opus_coupled_streams[avctx->channels - 1];
351         opus->stream_count   = avctx->channels - coupled_stream_count;
352         memcpy(libopus_channel_mapping,
353                opus_vorbis_channel_map[avctx->channels - 1],
354                avctx->channels * sizeof(*libopus_channel_mapping));
355 
356         enc = opus_multistream_encoder_create(
357             avctx->sample_rate, avctx->channels, opus->stream_count,
358             coupled_stream_count,
359             libavcodec_libopus_channel_map[avctx->channels - 1],
360             opus->opts.application, &ret);
361     } else {
362         /* Use the newer multistream API. The encoder will set the channel
363          * mapping and coupled stream counts to its internal defaults and will
364          * use surround masking analysis to save bits. */
365         mapping_family = opus->opts.mapping_family;
366         enc = opus_multistream_surround_encoder_create(
367             avctx->sample_rate, avctx->channels, mapping_family,
368             &opus->stream_count, &coupled_stream_count, libopus_channel_mapping,
369             opus->opts.application, &ret);
370     }
371 
372     if (ret != OPUS_OK) {
373         av_log(avctx, AV_LOG_ERROR,
374                "Failed to create encoder: %s\n", opus_strerror(ret));
375         return ff_opus_error_to_averror(ret);
376     }
377 
378     if (!avctx->bit_rate) {
379         /* Sane default copied from opusenc */
380         avctx->bit_rate = 64000 * opus->stream_count +
381                           32000 * coupled_stream_count;
382         av_log(avctx, AV_LOG_WARNING,
383                "No bit rate set. Defaulting to %"PRId64" bps.\n", avctx->bit_rate);
384     }
385 
386     if (avctx->bit_rate < 500 || avctx->bit_rate > 256000 * avctx->channels) {
387         av_log(avctx, AV_LOG_ERROR, "The bit rate %"PRId64" bps is unsupported. "
388                "Please choose a value between 500 and %d.\n", avctx->bit_rate,
389                256000 * avctx->channels);
390         ret = AVERROR(EINVAL);
391         goto fail;
392     }
393 
394     ret = libopus_configure_encoder(avctx, enc, &opus->opts);
395     if (ret != OPUS_OK) {
396         ret = ff_opus_error_to_averror(ret);
397         goto fail;
398     }
399 
400     /* Header includes channel mapping table if and only if mapping family is NOT 0 */
401     header_size = 19 + (mapping_family == 0 ? 0 : 2 + avctx->channels);
402     avctx->extradata = av_malloc(header_size + AV_INPUT_BUFFER_PADDING_SIZE);
403     if (!avctx->extradata) {
404         av_log(avctx, AV_LOG_ERROR, "Failed to allocate extradata.\n");
405         ret = AVERROR(ENOMEM);
406         goto fail;
407     }
408     avctx->extradata_size = header_size;
409 
410     opus->samples = av_mallocz_array(frame_size, avctx->channels *
411                                av_get_bytes_per_sample(avctx->sample_fmt));
412     if (!opus->samples) {
413         av_log(avctx, AV_LOG_ERROR, "Failed to allocate samples buffer.\n");
414         ret = AVERROR(ENOMEM);
415         goto fail;
416     }
417 
418     ret = opus_multistream_encoder_ctl(enc, OPUS_GET_LOOKAHEAD(&avctx->initial_padding));
419     if (ret != OPUS_OK)
420         av_log(avctx, AV_LOG_WARNING,
421                "Unable to get number of lookahead samples: %s\n",
422                opus_strerror(ret));
423 
424     libopus_write_header(avctx, opus->stream_count, coupled_stream_count,
425                          mapping_family, libopus_channel_mapping);
426 
427     ff_af_queue_init(avctx, &opus->afq);
428 
429     opus->enc = enc;
430 
431     return 0;
432 
433 fail:
434     opus_multistream_encoder_destroy(enc);
435     av_freep(&avctx->extradata);
436     return ret;
437 }
438 
libopus_copy_samples_with_channel_map(uint8_t * dst,const uint8_t * src,const uint8_t * channel_map,int nb_channels,int nb_samples,int bytes_per_sample)439 static void libopus_copy_samples_with_channel_map(
440     uint8_t *dst, const uint8_t *src, const uint8_t *channel_map,
441     int nb_channels, int nb_samples, int bytes_per_sample) {
442     int sample, channel;
443     for (sample = 0; sample < nb_samples; ++sample) {
444         for (channel = 0; channel < nb_channels; ++channel) {
445             const size_t src_pos = bytes_per_sample * (nb_channels * sample + channel);
446             const size_t dst_pos = bytes_per_sample * (nb_channels * sample + channel_map[channel]);
447 
448             memcpy(&dst[dst_pos], &src[src_pos], bytes_per_sample);
449         }
450     }
451 }
452 
libopus_encode(AVCodecContext * avctx,AVPacket * avpkt,const AVFrame * frame,int * got_packet_ptr)453 static int libopus_encode(AVCodecContext *avctx, AVPacket *avpkt,
454                           const AVFrame *frame, int *got_packet_ptr)
455 {
456     LibopusEncContext *opus = avctx->priv_data;
457     const int bytes_per_sample = av_get_bytes_per_sample(avctx->sample_fmt);
458     const int sample_size      = avctx->channels * bytes_per_sample;
459     uint8_t *audio;
460     int ret;
461     int discard_padding;
462 
463     if (frame) {
464         ret = ff_af_queue_add(&opus->afq, frame);
465         if (ret < 0)
466             return ret;
467         if (opus->encoder_channel_map != NULL) {
468             audio = opus->samples;
469             libopus_copy_samples_with_channel_map(
470                 audio, frame->data[0], opus->encoder_channel_map,
471                 avctx->channels, frame->nb_samples, bytes_per_sample);
472         } else if (frame->nb_samples < opus->opts.packet_size) {
473             audio = opus->samples;
474             memcpy(audio, frame->data[0], frame->nb_samples * sample_size);
475         } else
476             audio = frame->data[0];
477     } else {
478         if (!opus->afq.remaining_samples || (!opus->afq.frame_alloc && !opus->afq.frame_count))
479             return 0;
480         audio = opus->samples;
481         memset(audio, 0, opus->opts.packet_size * sample_size);
482     }
483 
484     /* Maximum packet size taken from opusenc in opus-tools. 120ms packets
485      * consist of 6 frames in one packet. The maximum frame size is 1275
486      * bytes along with the largest possible packet header of 7 bytes. */
487     if ((ret = ff_alloc_packet2(avctx, avpkt, (1275 * 6 + 7) * opus->stream_count, 0)) < 0)
488         return ret;
489 
490     if (avctx->sample_fmt == AV_SAMPLE_FMT_FLT)
491         ret = opus_multistream_encode_float(opus->enc, (float *)audio,
492                                             opus->opts.packet_size,
493                                             avpkt->data, avpkt->size);
494     else
495         ret = opus_multistream_encode(opus->enc, (opus_int16 *)audio,
496                                       opus->opts.packet_size,
497                                       avpkt->data, avpkt->size);
498 
499     if (ret < 0) {
500         av_log(avctx, AV_LOG_ERROR,
501                "Error encoding frame: %s\n", opus_strerror(ret));
502         return ff_opus_error_to_averror(ret);
503     }
504 
505     av_shrink_packet(avpkt, ret);
506 
507     ff_af_queue_remove(&opus->afq, opus->opts.packet_size,
508                        &avpkt->pts, &avpkt->duration);
509 
510     discard_padding = opus->opts.packet_size - avpkt->duration;
511     // Check if subtraction resulted in an overflow
512     if ((discard_padding < opus->opts.packet_size) != (avpkt->duration > 0)) {
513         av_packet_unref(avpkt);
514         return AVERROR(EINVAL);
515     }
516     if (discard_padding > 0) {
517         uint8_t* side_data = av_packet_new_side_data(avpkt,
518                                                      AV_PKT_DATA_SKIP_SAMPLES,
519                                                      10);
520         if(!side_data) {
521             av_packet_unref(avpkt);
522             return AVERROR(ENOMEM);
523         }
524         AV_WL32(side_data + 4, discard_padding);
525     }
526 
527     *got_packet_ptr = 1;
528 
529     return 0;
530 }
531 
libopus_encode_close(AVCodecContext * avctx)532 static av_cold int libopus_encode_close(AVCodecContext *avctx)
533 {
534     LibopusEncContext *opus = avctx->priv_data;
535 
536     opus_multistream_encoder_destroy(opus->enc);
537 
538     ff_af_queue_close(&opus->afq);
539 
540     av_freep(&opus->samples);
541     av_freep(&avctx->extradata);
542 
543     return 0;
544 }
545 
546 #define OFFSET(x) offsetof(LibopusEncContext, opts.x)
547 #define FLAGS AV_OPT_FLAG_AUDIO_PARAM | AV_OPT_FLAG_ENCODING_PARAM
548 static const AVOption libopus_options[] = {
549     { "application",    "Intended application type",           OFFSET(application),    AV_OPT_TYPE_INT,   { .i64 = OPUS_APPLICATION_AUDIO }, OPUS_APPLICATION_VOIP, OPUS_APPLICATION_RESTRICTED_LOWDELAY, FLAGS, "application" },
550         { "voip",           "Favor improved speech intelligibility",   0, AV_OPT_TYPE_CONST, { .i64 = OPUS_APPLICATION_VOIP },                0, 0, FLAGS, "application" },
551         { "audio",          "Favor faithfulness to the input",         0, AV_OPT_TYPE_CONST, { .i64 = OPUS_APPLICATION_AUDIO },               0, 0, FLAGS, "application" },
552         { "lowdelay",       "Restrict to only the lowest delay modes", 0, AV_OPT_TYPE_CONST, { .i64 = OPUS_APPLICATION_RESTRICTED_LOWDELAY }, 0, 0, FLAGS, "application" },
553     { "frame_duration", "Duration of a frame in milliseconds", OFFSET(frame_duration), AV_OPT_TYPE_FLOAT, { .dbl = 20.0 }, 2.5, 120.0, FLAGS },
554     { "packet_loss",    "Expected packet loss percentage",     OFFSET(packet_loss),    AV_OPT_TYPE_INT,   { .i64 = 0 },    0,   100,  FLAGS },
555     { "fec",             "Enable inband FEC. Expected packet loss must be non-zero",     OFFSET(fec),    AV_OPT_TYPE_BOOL,   { .i64 = 0 }, 0, 1, FLAGS },
556     { "vbr",            "Variable bit rate mode",              OFFSET(vbr),            AV_OPT_TYPE_INT,   { .i64 = 1 },    0,   2,    FLAGS, "vbr" },
557         { "off",            "Use constant bit rate", 0, AV_OPT_TYPE_CONST, { .i64 = 0 }, 0, 0, FLAGS, "vbr" },
558         { "on",             "Use variable bit rate", 0, AV_OPT_TYPE_CONST, { .i64 = 1 }, 0, 0, FLAGS, "vbr" },
559         { "constrained",    "Use constrained VBR",   0, AV_OPT_TYPE_CONST, { .i64 = 2 }, 0, 0, FLAGS, "vbr" },
560     { "mapping_family", "Channel Mapping Family",              OFFSET(mapping_family), AV_OPT_TYPE_INT,   { .i64 = -1 },   -1,  255,  FLAGS, "mapping_family" },
561 #ifdef OPUS_SET_PHASE_INVERSION_DISABLED_REQUEST
562     { "apply_phase_inv", "Apply intensity stereo phase inversion", OFFSET(apply_phase_inv), AV_OPT_TYPE_BOOL, { .i64 = 1 }, 0, 1, FLAGS },
563 #endif
564     { NULL },
565 };
566 
567 static const AVClass libopus_class = {
568     .class_name = "libopus",
569     .item_name  = av_default_item_name,
570     .option     = libopus_options,
571     .version    = LIBAVUTIL_VERSION_INT,
572 };
573 
574 static const AVCodecDefault libopus_defaults[] = {
575     { "b",                 "0" },
576     { "compression_level", "10" },
577     { NULL },
578 };
579 
580 static const int libopus_sample_rates[] = {
581     48000, 24000, 16000, 12000, 8000, 0,
582 };
583 
584 AVCodec ff_libopus_encoder = {
585     .name            = "libopus",
586     .long_name       = NULL_IF_CONFIG_SMALL("libopus Opus"),
587     .type            = AVMEDIA_TYPE_AUDIO,
588     .id              = AV_CODEC_ID_OPUS,
589     .priv_data_size  = sizeof(LibopusEncContext),
590     .init            = libopus_encode_init,
591     .encode2         = libopus_encode,
592     .close           = libopus_encode_close,
593     .capabilities    = AV_CODEC_CAP_DELAY | AV_CODEC_CAP_SMALL_LAST_FRAME,
594     .sample_fmts     = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_S16,
595                                                       AV_SAMPLE_FMT_FLT,
596                                                       AV_SAMPLE_FMT_NONE },
597     .supported_samplerates = libopus_sample_rates,
598     .priv_class      = &libopus_class,
599     .defaults        = libopus_defaults,
600     .wrapper_name    = "libopus",
601 };
602