text: /*
   * Opus encoder using libopus
   * Copyright (c) 2012 Nathan Caldwell
   *
   * This file is part of FFmpeg.
   *
   * FFmpeg is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * FFmpeg is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with FFmpeg; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
   */
  
  #include <opus.h>
  #include <opus_multistream.h>
  
  #include "libavutil/opt.h"
  #include "avcodec.h"
  #include "bytestream.h"
  #include "internal.h"
  #include "libopus.h"
  #include "vorbis.h"
  #include "audio_frame_queue.h"
  
  typedef struct LibopusEncOpts {
      int vbr;
      int application;
      int packet_loss;
      int complexity;
      float frame_duration;
      int packet_size;
      int max_bandwidth;
  } LibopusEncOpts;
  
  typedef struct LibopusEncContext {
      AVClass *class;
      OpusMSEncoder *enc;
      int stream_count;
      uint8_t *samples;
      LibopusEncOpts opts;
      AudioFrameQueue afq;
  } LibopusEncContext;
  
  static const uint8_t opus_coupled_streams[8] = {
      0, 1, 1, 2, 2, 2, 2, 3
  };
  
  /* Opus internal to Vorbis channel order mapping written in the header */
  static const uint8_t opus_vorbis_channel_map[8][8] = {
      { 0 },
      { 0, 1 },
      { 0, 2, 1 },
      { 0, 1, 2, 3 },
      { 0, 4, 1, 2, 3 },
      { 0, 4, 1, 2, 3, 5 },
      { 0, 4, 1, 2, 3, 5, 6 },
      { 0, 6, 1, 2, 3, 4, 5, 7 },
  };
  
  /* libavcodec to libopus channel order mapping, passed to libopus */
  static const uint8_t libavcodec_libopus_channel_map[8][8] = {
      { 0 },
      { 0, 1 },
      { 0, 1, 2 },
      { 0, 1, 2, 3 },
      { 0, 1, 3, 4, 2 },
      { 0, 1, 4, 5, 2, 3 },
      { 0, 1, 5, 6, 2, 4, 3 },
      { 0, 1, 6, 7, 4, 5, 2, 3 },
  };
  
  static void libopus_write_header(AVCodecContext *avctx, int stream_count,
                                   int coupled_stream_count,
                                   const uint8_t *channel_mapping)
  {
      uint8_t *p   = avctx->extradata;
      int channels = avctx->channels;
  
      bytestream_put_buffer(&p, "OpusHead", 8);
      bytestream_put_byte(&p, 1); /* Version */
      bytestream_put_byte(&p, channels);
      bytestream_put_le16(&p, avctx->delay); /* Lookahead samples at 48kHz */
      bytestream_put_le32(&p, avctx->sample_rate); /* Original sample rate */
      bytestream_put_le16(&p, 0); /* Gain of 0dB is recommended. */
  
      /* Channel mapping */
      if (channels > 2) {
          bytestream_put_byte(&p, channels <= 8 ? 1 : 255);
          bytestream_put_byte(&p, stream_count);
          bytestream_put_byte(&p, coupled_stream_count);
          bytestream_put_buffer(&p, channel_mapping, channels);
      } else {
          bytestream_put_byte(&p, 0);
      }
  }
  
  static int libopus_configure_encoder(AVCodecContext *avctx, OpusMSEncoder *enc,
                                       LibopusEncOpts *opts)
  {
      int ret;
  
      ret = opus_multistream_encoder_ctl(enc, OPUS_SET_BITRATE(avctx->bit_rate));
      if (ret != OPUS_OK) {
          av_log(avctx, AV_LOG_ERROR,
                 "Failed to set bitrate: %s\n", opus_strerror(ret));
          return ret;
      }
  
      ret = opus_multistream_encoder_ctl(enc,
                                         OPUS_SET_COMPLEXITY(opts->complexity));
      if (ret != OPUS_OK)
          av_log(avctx, AV_LOG_WARNING,
                 "Unable to set complexity: %s\n", opus_strerror(ret));
  
      ret = opus_multistream_encoder_ctl(enc, OPUS_SET_VBR(!!opts->vbr));
      if (ret != OPUS_OK)
          av_log(avctx, AV_LOG_WARNING,
                 "Unable to set VBR: %s\n", opus_strerror(ret));
  
      ret = opus_multistream_encoder_ctl(enc,
                                         OPUS_SET_VBR_CONSTRAINT(opts->vbr == 2));
      if (ret != OPUS_OK)
          av_log(avctx, AV_LOG_WARNING,
                 "Unable to set constrained VBR: %s\n", opus_strerror(ret));
  
      ret = opus_multistream_encoder_ctl(enc,
                                         OPUS_SET_PACKET_LOSS_PERC(opts->packet_loss));
      if (ret != OPUS_OK)
          av_log(avctx, AV_LOG_WARNING,
                 "Unable to set expected packet loss percentage: %s\n",
                 opus_strerror(ret));
  
      if (avctx->cutoff) {
          ret = opus_multistream_encoder_ctl(enc,
                                             OPUS_SET_MAX_BANDWIDTH(opts->max_bandwidth));
          if (ret != OPUS_OK)
              av_log(avctx, AV_LOG_WARNING,
                     "Unable to set maximum bandwidth: %s\n", opus_strerror(ret));
      }
  
      return OPUS_OK;
  }
  
  static int av_cold libopus_encode_init(AVCodecContext *avctx)
  {
      LibopusEncContext *opus = avctx->priv_data;
      const uint8_t *channel_mapping;
      OpusMSEncoder *enc;
      int ret = OPUS_OK;
      int coupled_stream_count, header_size, frame_size;
  
      coupled_stream_count = opus_coupled_streams[avctx->channels - 1];
      opus->stream_count   = avctx->channels - coupled_stream_count;
      channel_mapping      = libavcodec_libopus_channel_map[avctx->channels - 1];
  
      /* FIXME: Opus can handle up to 255 channels. However, the mapping for
       * anything greater than 8 is undefined. */
      if (avctx->channels > 8)
          av_log(avctx, AV_LOG_WARNING,
                 "Channel layout undefined for %d channels.\n", avctx->channels);
  
      if (!avctx->bit_rate) {
          /* Sane default copied from opusenc */
          avctx->bit_rate = 64000 * opus->stream_count +
                            32000 * coupled_stream_count;
          av_log(avctx, AV_LOG_WARNING,
                 "No bit rate set. Defaulting to %d bps.\n", avctx->bit_rate);
      }
  
      if (avctx->bit_rate < 500 || avctx->bit_rate > 256000 * avctx->channels) {
          av_log(avctx, AV_LOG_ERROR, "The bit rate %d bps is unsupported. "
                 "Please choose a value between 500 and %d.\n", avctx->bit_rate,
                 256000 * avctx->channels);
          return AVERROR(EINVAL);
      }
  
      frame_size = opus->opts.frame_duration * 48000 / 1000;
      switch (frame_size) {
      case 120:
      case 240:
          if (opus->opts.application != OPUS_APPLICATION_RESTRICTED_LOWDELAY)
              av_log(avctx, AV_LOG_WARNING,
                     "LPC mode cannot be used with a frame duration of less "
                     "than 10ms. Enabling restricted low-delay mode.\n"
                     "Use a longer frame duration if this is not what you want.\n");
          /* Frame sizes less than 10 ms can only use MDCT mode, so switching to
           * RESTRICTED_LOWDELAY avoids an unnecessary extra 2.5ms lookahead. */
          opus->opts.application = OPUS_APPLICATION_RESTRICTED_LOWDELAY;
      case 480:
      case 960:
      case 1920:
      case 2880:
          opus->opts.packet_size =
          avctx->frame_size      = frame_size * avctx->sample_rate / 48000;
          break;
      default:
          av_log(avctx, AV_LOG_ERROR, "Invalid frame duration: %g.\n"
                 "Frame duration must be exactly one of: 2.5, 5, 10, 20, 40 or 60.\n",
                 opus->opts.frame_duration);
          return AVERROR(EINVAL);
      }
  
      if (avctx->compression_level < 0 || avctx->compression_level > 10) {
          av_log(avctx, AV_LOG_WARNING,
                 "Compression level must be in the range 0 to 10. "
                 "Defaulting to 10.\n");
          opus->opts.complexity = 10;
      } else {
          opus->opts.complexity = avctx->compression_level;
      }
  
      if (avctx->cutoff) {
          switch (avctx->cutoff) {
          case  4000:
              opus->opts.max_bandwidth = OPUS_BANDWIDTH_NARROWBAND;
              break;
          case  6000:
              opus->opts.max_bandwidth = OPUS_BANDWIDTH_MEDIUMBAND;
              break;
          case  8000:
              opus->opts.max_bandwidth = OPUS_BANDWIDTH_WIDEBAND;
              break;
          case 12000:
              opus->opts.max_bandwidth = OPUS_BANDWIDTH_SUPERWIDEBAND;
              break;
          case 20000:
              opus->opts.max_bandwidth = OPUS_BANDWIDTH_FULLBAND;
              break;
          default:
              av_log(avctx, AV_LOG_WARNING,
                     "Invalid frequency cutoff: %d. Using default maximum bandwidth.\n"
                     "Cutoff frequency must be exactly one of: 4000, 6000, 8000, 12000 or 20000.\n",
                     avctx->cutoff);
              avctx->cutoff = 0;
          }
      }
  
      enc = opus_multistream_encoder_create(avctx->sample_rate, avctx->channels,
                                            opus->stream_count,
                                            coupled_stream_count,
                                            channel_mapping,
                                            opus->opts.application, &ret);
      if (ret != OPUS_OK) {
          av_log(avctx, AV_LOG_ERROR,
                 "Failed to create encoder: %s\n", opus_strerror(ret));
          return ff_opus_error_to_averror(ret);
      }
  
      ret = libopus_configure_encoder(avctx, enc, &opus->opts);
      if (ret != OPUS_OK) {
          ret = ff_opus_error_to_averror(ret);
          goto fail;
      }
  
      header_size = 19 + (avctx->channels > 2 ? 2 + avctx->channels : 0);
      avctx->extradata = av_malloc(header_size + FF_INPUT_BUFFER_PADDING_SIZE);
      if (!avctx->extradata) {
          av_log(avctx, AV_LOG_ERROR, "Failed to allocate extradata.\n");
          ret = AVERROR(ENOMEM);
          goto fail;
      }
      avctx->extradata_size = header_size;
  
      opus->samples = av_mallocz(frame_size * avctx->channels *
                                 av_get_bytes_per_sample(avctx->sample_fmt));
      if (!opus->samples) {
          av_log(avctx, AV_LOG_ERROR, "Failed to allocate samples buffer.\n");
          ret = AVERROR(ENOMEM);
          goto fail;
      }
  
      ret = opus_multistream_encoder_ctl(enc, OPUS_GET_LOOKAHEAD(&avctx->delay));
      if (ret != OPUS_OK)
          av_log(avctx, AV_LOG_WARNING,
                 "Unable to get number of lookahead samples: %s\n",
                 opus_strerror(ret));
  
      libopus_write_header(avctx, opus->stream_count, coupled_stream_count,
                           opus_vorbis_channel_map[avctx->channels - 1]);
  
      ff_af_queue_init(avctx, &opus->afq);
  
      opus->enc = enc;
  
      return 0;
  
  fail:
      opus_multistream_encoder_destroy(enc);
      av_freep(&avctx->extradata);
      return ret;
  }
  
  static int libopus_encode(AVCodecContext *avctx, AVPacket *avpkt,
                            const AVFrame *frame, int *got_packet_ptr)
  {
      LibopusEncContext *opus = avctx->priv_data;
      const int sample_size   = avctx->channels *
                                av_get_bytes_per_sample(avctx->sample_fmt);
      uint8_t *audio;
      int ret;
  
      if (frame) {
          ff_af_queue_add(&opus->afq, frame);
          if (frame->nb_samples < opus->opts.packet_size) {
              audio = opus->samples;
              memcpy(audio, frame->data[0], frame->nb_samples * sample_size);
          } else
              audio = frame->data[0];
      } else {
          if (!opus->afq.remaining_samples)
              return 0;
          audio = opus->samples;
          memset(audio, 0, opus->opts.packet_size * sample_size);
      }
  
      /* Maximum packet size taken from opusenc in opus-tools. 60ms packets
       * consist of 3 frames in one packet. The maximum frame size is 1275
       * bytes along with the largest possible packet header of 7 bytes. */
      if (ret = ff_alloc_packet(avpkt, (1275 * 3 + 7) * opus->stream_count)) {
          av_log(avctx, AV_LOG_ERROR, "Error getting output packet\n");
          return ret;
      }
  
      if (avctx->sample_fmt == AV_SAMPLE_FMT_FLT)
          ret = opus_multistream_encode_float(opus->enc, (float *)audio,
                                              opus->opts.packet_size,
                                              avpkt->data, avpkt->size);
      else
          ret = opus_multistream_encode(opus->enc, (opus_int16 *)audio,
                                        opus->opts.packet_size,
                                        avpkt->data, avpkt->size);
  
      if (ret < 0) {
          av_log(avctx, AV_LOG_ERROR,
                 "Error encoding frame: %s\n", opus_strerror(ret));
          return ff_opus_error_to_averror(ret);
      }
  
      av_shrink_packet(avpkt, ret);
  
      ff_af_queue_remove(&opus->afq, opus->opts.packet_size,
                         &avpkt->pts, &avpkt->duration);
  
      *got_packet_ptr = 1;
  
      return 0;
  }
  
  static int av_cold libopus_encode_close(AVCodecContext *avctx)
  {
      LibopusEncContext *opus = avctx->priv_data;
  
      opus_multistream_encoder_destroy(opus->enc);
  
      ff_af_queue_close(&opus->afq);
  
      av_freep(&opus->samples);
      av_freep(&avctx->extradata);
  
      return 0;
  }
  
  #define OFFSET(x) offsetof(LibopusEncContext, opts.x)
  #define FLAGS AV_OPT_FLAG_AUDIO_PARAM | AV_OPT_FLAG_ENCODING_PARAM
  static const AVOption libopus_options[] = {
      { "application",    "Intended application type",           OFFSET(application),    AV_OPT_TYPE_INT,   { .i64 = OPUS_APPLICATION_AUDIO }, OPUS_APPLICATION_VOIP, OPUS_APPLICATION_RESTRICTED_LOWDELAY, FLAGS, "application" },
          { "voip",           "Favor improved speech intelligibility",   0, AV_OPT_TYPE_CONST, { .i64 = OPUS_APPLICATION_VOIP },                0, 0, FLAGS, "application" },
          { "audio",          "Favor faithfulness to the input",         0, AV_OPT_TYPE_CONST, { .i64 = OPUS_APPLICATION_AUDIO },               0, 0, FLAGS, "application" },
          { "lowdelay",       "Restrict to only the lowest delay modes", 0, AV_OPT_TYPE_CONST, { .i64 = OPUS_APPLICATION_RESTRICTED_LOWDELAY }, 0, 0, FLAGS, "application" },
      { "frame_duration", "Duration of a frame in milliseconds", OFFSET(frame_duration), AV_OPT_TYPE_FLOAT, { .dbl = 10.0 }, 2.5, 60.0, FLAGS },
      { "packet_loss",    "Expected packet loss percentage",     OFFSET(packet_loss),    AV_OPT_TYPE_INT,   { .i64 = 0 },    0,   100,  FLAGS },
      { "vbr",            "Variable bit rate mode",              OFFSET(vbr),            AV_OPT_TYPE_INT,   { .i64 = 1 },    0,   2,    FLAGS, "vbr" },
          { "off",            "Use constant bit rate", 0, AV_OPT_TYPE_CONST, { .i64 = 0 }, 0, 0, FLAGS, "vbr" },
          { "on",             "Use variable bit rate", 0, AV_OPT_TYPE_CONST, { .i64 = 1 }, 0, 0, FLAGS, "vbr" },
          { "constrained",    "Use constrained VBR",   0, AV_OPT_TYPE_CONST, { .i64 = 2 }, 0, 0, FLAGS, "vbr" },
      { NULL },
  };
  
  static const AVClass libopus_class = {
      .class_name = "libopus",
      .item_name  = av_default_item_name,
      .option     = libopus_options,
      .version    = LIBAVUTIL_VERSION_INT,
  };
  
  static const AVCodecDefault libopus_defaults[] = {
      { "b",                 "0" },
      { "compression_level", "10" },
      { NULL },
  };
  
  static const int libopus_sample_rates[] = {
      48000, 24000, 16000, 12000, 8000, 0,
  };
  
  AVCodec ff_libopus_encoder = {
      .name            = "libopus",
      .type            = AVMEDIA_TYPE_AUDIO,
      .id              = AV_CODEC_ID_OPUS,
      .priv_data_size  = sizeof(LibopusEncContext),
      .init            = libopus_encode_init,
      .encode2         = libopus_encode,
      .close           = libopus_encode_close,
      .capabilities    = CODEC_CAP_DELAY | CODEC_CAP_SMALL_LAST_FRAME,
      .sample_fmts     = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_S16,
                                                        AV_SAMPLE_FMT_FLT,
                                                        AV_SAMPLE_FMT_NONE },
      .channel_layouts = ff_vorbis_channel_layouts,
      .supported_samplerates = libopus_sample_rates,
      .long_name       = NULL_IF_CONFIG_SMALL("libopus Opus"),
      .priv_class      = &libopus_class,
      .defaults        = libopus_defaults,
  };
  