Decode Opus in C#

using OneAudio;
using OneAudio.Opus;
 
// Ogg Opus files always decode at 48 kHz, whatever rate the encoder was given.
using (IAudioDecoder decoder = Audio.Open("music.opus"))
{
    AudioFormat f = decoder.Format;
    Console.WriteLine($"music.opus: {decoder.GetType().Name}, {f.SampleRate} Hz, " +
                      $"{f.Channels} ch, {decoder.LengthFrames / 48000.0:F3} s");
}
 
// Load it at the rate your app uses.
AudioClip clip = Audio.Load("music.opus", new LoadOptions { SampleRate = 44100 });
Console.WriteLine($"as 44.1 kHz: {clip.Frames} frames");
 
// Raw Opus packets, from a voice chat or a WebRTC stream, go through
// OpusDecoder. Here they come from OpusEncoder: 20 ms of a 440 Hz tone each.
var encoder = new OpusEncoder(new OpusEncoderSettings
{
    Channels = 1,
    Application = OpusApplication.Voip,
    BitrateBps = 24_000,
});
var packetDecoder = new OpusDecoder(sampleRate: 48000, channels: 1);
float[] pcm = new float[960];                               // 20 ms at 48 kHz
float[] decoded = new float[OpusPacket.MaxSamplesPer48k];   // the longest packet
byte[] packet = new byte[1500];
int bytes = 0, samples = 0;
for (int p = 0; p < 50; p++)                                // one second
{
    for (int i = 0; i < pcm.Length; i++)
        pcm[i] = 0.3f * MathF.Sin(2 * MathF.PI * 440 * (p * 960 + i) / 48000f);
    int length = encoder.Encode(pcm, 960, packet);
    bytes += length;
    samples += packetDecoder.Decode(packet.AsSpan(0, length), decoded);
}
Console.WriteLine($"50 packets, {bytes:N0} bytes, {samples} samples decoded");
 
// A lost packet: the decoder fills the gap. The span's length sets how much,
// here one 20 ms frame.
int concealed = packetDecoder.DecodePacketLoss(decoded.AsSpan(0, 960));
Console.WriteLine($"concealed {concealed} samples");

music.opus: OpusStreamDecoder, 48000 Hz, 2 ch, 32.000 s
as 44.1 kHz: 1411200 frames
50 packets, 3,161 bytes, 48000 samples decoded
concealed 960 samples