libopus

Abstract	libopus
Authors	Walter Fan
Status	WIP
Updated	2024-08-21

Overview 

Installation 

wget https://downloads.xiph.org/releases/opus/opus-1.4.tar.gz
tar xvfz opus-1.4.tar.gz
cd opus-1.4
./configure
make
make install

Usage 

initialize encoder 

int init_encoder(OpusEncoder*& pEncoder, int sampleRate, int numberOfChannels, int bitrate) {

    int err;
    pEncoder = opus_encoder_create(sampleRate, numberOfChannels, OPUS_APPLICATION_VOIP, &err);
    if (err < 0) { return err; }

    opus_encoder_ctl(encoder, OPUS_SET_COMPLEXITY(4));
    opus_encoder_ctl(encoder, OPUS_SET_BITRATE(bitrate));
    opus_encoder_ctl(encoder, OPUS_SET_MAX_BANDWIDTH(OPUS_BANDWIDTH_WIDEBAND));
    opus_encoder_ctl(encoder, OPUS_SET_INBAND_FEC(1));
    opus_encoder_ctl(encoder, OPUS_SET_PACKET_LOSS_PERC(100));
    opus_encoder_ctl(encoder, OPUS_SET_DTX(1));

    return err;
}

encode 

int encode_audio(OpusEncoder* encoder, float* pcm, int frameSize, std::vector<uint8_t>& result) {

    unsigned char output[MAX_PACKET_SIZE];
    int size;

    size = opus_encode_float(encoder, pcm, frameSize, output, MAX_PACKET_SIZE);
    if (size < 0) {
        return size;
    }

    std::vector<uint8_t> encoded_data(output, output + size);
    result.swap(encoded_data);

    return size;
}

initialize decoder 

int initialize_decoder(OpusDecoder*& decoder; int peerId, int sampleRate, int numberOfChannels) {

    int err;
    decoder = opus_decoder_create(sampleRate, numberOfChannels, &err);
    return err;
}

decode 

int decode_audio(OpusDecoder* decoder, unsigned char* data, int length, int peerId, int numberOfChannels, int maxFrameSize, td::vector<uint8_t>& result) {

    float output[numberOfChannels * maxFrameSize];
    int size;

    size = opus_decode_float(decoder, data, length, output, maxFrameSize, 0);
    if (size < 0) {
        return size;
    }

    std::vector<uint8_t> encoded_data(output, output + size);
    result.swap(encoded_data);

    return size;
}