static av_cold int libopus_decode_init(AVCodecContext *avc) { struct libopus_context *opus = avc->priv_data; int ret, channel_map = 0, gain_db = 0, nb_streams, nb_coupled; uint8_t mapping_arr[8] = { 0, 1 }, *mapping; avc->sample_rate = 48000; avc->sample_fmt = avc->request_sample_fmt == AV_SAMPLE_FMT_FLT ? AV_SAMPLE_FMT_FLT : AV_SAMPLE_FMT_S16; avc->channel_layout = avc->channels > 8 ? 0 : ff_vorbis_channel_layouts[avc->channels - 1]; if (avc->extradata_size >= OPUS_HEAD_SIZE) { gain_db = sign_extend(AV_RL16(avc->extradata + 16), 16); channel_map = AV_RL8 (avc->extradata + 18); if (avc->extradata_size >= OPUS_HEAD_SIZE + 2 + avc->channels) { nb_streams = avc->extradata[OPUS_HEAD_SIZE + 0]; nb_coupled = avc->extradata[OPUS_HEAD_SIZE + 1]; if (nb_streams + nb_coupled != avc->channels) av_log(avc, AV_LOG_WARNING, "Inconsistent channel mapping.\n"); mapping = avc->extradata + OPUS_HEAD_SIZE + 2; } else { if (avc->channels > 2 || channel_map) { av_log(avc, AV_LOG_ERROR, "No channel mapping for %d channels.\n", avc->channels); return AVERROR(EINVAL); nb_streams = 1; nb_coupled = avc->channels > 1; mapping = mapping_arr; if (avc->channels > 2 && avc->channels <= 8) { const uint8_t *vorbis_offset = ff_vorbis_channel_layout_offsets[avc->channels - 1]; int ch; /* Remap channels from Vorbis order to libav order */ for (ch = 0; ch < avc->channels; ch++) mapping_arr[ch] = mapping[vorbis_offset[ch]]; mapping = mapping_arr; opus->dec = opus_multistream_decoder_create(avc->sample_rate, avc->channels, nb_streams, nb_coupled, mapping, &ret); if (!opus->dec) { av_log(avc, AV_LOG_ERROR, "Unable to create decoder: %s\n", opus_strerror(ret)); return ff_opus_error_to_averror(ret); ret = opus_multistream_decoder_ctl(opus->dec, OPUS_SET_GAIN(gain_db)); if (ret != OPUS_OK) av_log(avc, AV_LOG_WARNING, "Failed to set gain: %s\n", opus_strerror(ret)); avc->delay = 3840; /* Decoder delay (in samples) at 48kHz */ return 0;