using (var encoder = new OpusEncoder(OpusOptimizer.Clarity, OpusSampleRate.48k, OpusAudioChannels.Stereo)
{
    VBR = true // Variable bitrate
})
using (var decoder = new OpusDecoder(48000, 2))
{
    // 40 ms of silence at 48 KHz (2 channels).
    byte[] inputPCMBytes = new byte[40 * 48000 / 1000 * 2 * 2];
    byte[] opusBytes = encoder.Encode(inputPCMBytes, inputPCMBytes.Length, out int encodedLength);
    byte[] outputPCMBytes = decoder.Decode(opusBytes, encodedLength, out int decodedLength);
}