func: 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      = libav_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;
  
  }
  