Decode audio from a stream

using System.Diagnostics;
using OneAudio;
 
// A stream that can't seek, like a network response or a pipe: here the
// output of `cat`.
var cat = Process.Start(new ProcessStartInfo("cat", "music.ogg")
{
    RedirectStandardOutput = true,
})!;
Stream pipe = cat.StandardOutput.BaseStream;
Console.WriteLine($"pipe: CanSeek {pipe.CanSeek}");
 
// Limits for input you don't trust. Sizes read from the file are checked
// before anything is allocated.
var limits = new AudioLimits { MaxChannels = 2, MaxSampleRate = 48000 };
using var cancel = new CancellationTokenSource(TimeSpan.FromSeconds(30));
 
using IAudioDecoder decoder = Audio.Open(pipe, leaveOpen: false, limits, cancel.Token);
int channels = decoder.Format.Channels;
Console.WriteLine($"{decoder.Format.SampleRate} Hz, {channels} ch, CanSeek {decoder.CanSeek}");
 
// Block by block: memory use doesn't grow with the length of the file.
float[] block = new float[1024 * channels];
long frames = 0;
double sumSquares = 0;
int read;
while ((read = decoder.Read(block)) > 0)
{
    foreach (float s in block.AsSpan(0, read * channels))
        sumSquares += s * s;
    frames += read;
}
double rms = 10 * Math.Log10(sumSquares / (frames * channels));
Console.WriteLine($"{frames} frames, RMS {rms:F1} dBFS");
 
try
{
    decoder.Seek(0);
}
catch (NotSupportedException)
{
    Console.WriteLine("Seek on a pipe: NotSupportedException");
}
 
// A file over the limits is refused with an exception that names the limit.
try
{
    using IAudioDecoder tooBig = Audio.Open("music.wav", new AudioLimits { MaxSampleRate = 32000 });
}
catch (AudioLimitExceededException e)
{
    Console.WriteLine(e.Message);
}
 
// Bytes that aren't audio at all.
try
{
    using IAudioDecoder notAudio = Audio.Open(new MemoryStream("not audio"u8.ToArray()));
}
catch (UnsupportedAudioFormatException e)
{
    Console.WriteLine($"{e.GetType().Name}: {e.Message}");
}

pipe: CanSeek False
44100 Hz, 2 ch, CanSeek False
1411200 frames, RMS -24.8 dBFS
Seek on a pipe: NotSupportedException
MaxSampleRate limit exceeded: input needs 44100, limit is 32000.
UnsupportedAudioFormatException: No registered container format recognises this data.