---
title: "Convert audio files"
url: https://recursiveai.org/oneaudio/cookbook/convert-audio-files/
description: "Convert MP3, Ogg Vorbis, Opus, FLAC and WAV files to WAV, FLAC or Ogg Opus in C# with oneaudio, change the sample rate and channels on the way, and…"
version: "1.2.1"
---

# Convert audio files

Convert MP3, Ogg Vorbis, Opus, FLAC and WAV files to WAV, FLAC or Ogg Opus in C# with oneaudio, change the sample rate and channels on the way, and convert streams in memory.

```csharp
using OneAudio;

// Every format can be read; WAV, FLAC and Ogg Opus can be written.
string[] inputs = ["music.mp3", "music.ogg", "music.opus", "music.flac", "music.wav"];
foreach (string input in inputs)
{
    string ext = Path.GetExtension(input).TrimStart('.');
    string output = $"music-from-{ext}.flac";
    TranscodeResult r = Audio.Transcode(input, output);
    long size = new FileInfo(output).Length;
    Console.WriteLine($"{input,-10} -> {output,-20} {r.Frames,7} frames, " +
                      $"{r.Input.SampleRate} Hz, {size,7:N0} bytes");
}

// Convert rate and channels on the way: a 16 kHz mono line to 48 kHz stereo.
var options = new TranscodeOptions { SampleRate = 48000, Channels = 2 };
TranscodeResult voice = Audio.Transcode("voice.wav", "voice.opus", options);
Console.WriteLine($"voice.opus: {voice.Input.Channels} ch at {voice.Input.SampleRate} Hz, " +
                  $"{voice.Frames} frames");

// Streams have no file name, so the format must be given.
using (var input = File.OpenRead("music.ogg"))
using (var output = new MemoryStream())
{
    Audio.Transcode(input, output, new TranscodeOptions { Format = AudioFileFormat.Wav });
    Console.WriteLine($"music.ogg to WAV in memory: {output.Length:N0} bytes");
}

// MP3, Vorbis and AAC can't be written.
try
{
    Audio.Transcode("music.wav", "music-out.mp3");
}
catch (ArgumentException e)
{
    Console.WriteLine(e.Message);
}
```

```text
music.mp3  -> music-from-mp3.flac  1411200 frames, 44100 Hz, 890,883 bytes
music.ogg  -> music-from-ogg.flac  1411200 frames, 44100 Hz, 867,043 bytes
music.opus -> music-from-opus.flac 1536000 frames, 48000 Hz, 998,012 bytes
music.flac -> music-from-flac.flac 1411200 frames, 44100 Hz, 813,193 bytes
music.wav  -> music-from-wav.flac  1411200 frames, 44100 Hz, 813,193 bytes
voice.opus: 2 ch at 48000 Hz, 289200 frames
music.ogg to WAV in memory: 5,644,880 bytes
Cannot tell the output format from the extension '.mp3'; use .wav, .flac or .opus, or set TranscodeOptions.Format. (Parameter 'path')
```

## What can be written

| From | To WAV | To FLAC | To Ogg Opus |
|---|---|---|---|
| Integer WAV, FLAC | Bit-exact, same depth | Bit-exact, same depth | Lossy |
| Float WAV | Same float type | 16-bit by default | Lossy |
| MP3, Ogg Vorbis, Ogg Opus | 16-bit PCM by default | 16-bit by default | Lossy, again |

Bit-exact holds when nothing is converted. A change of rate or channels goes through floats, and converted 24 and 32-bit audio is written to FLAC at 24 bits.

- The output format comes from the extension: `.wav` or `.wave`, `.flac`, and `.opus`, `.ogg` or `.oga` for Ogg Opus. Set `TranscodeOptions.Format` to choose it yourself. A stream has no extension, so it needs `Format`.
- There’s no MP3, Vorbis or AAC encoder. An `.mp3` output path throws `ArgumentException`, and `.ogg` writes Opus, not Vorbis.
- `SampleRate` and `Channels` in `TranscodeOptions` convert on the way. Mono becomes two or more channels as a copy on the front pair. Other changes fold speakers down: the center goes into left and right at −3 dB, and stereo to mono takes each side at −6 dB. Folded sums aren’t normalized, so loud multichannel audio can pass full scale.
- The conversion streams block by block, so memory use doesn’t depend on the length. If it fails, the partial output file is deleted.
- `music.opus` converts at 48 kHz, the rate Opus decodes at. Add `SampleRate = 44100` to get the source rate back.
- `music-from-wav.flac` and `music-from-flac.flac` are byte-identical: the same samples and the same settings give the same bytes.

The encoder settings are `TranscodeOptions.Wav`, `Flac` and `Opus`. See [Read and write WAV](https://recursiveai.org/oneaudio/cookbook/wav/), [Read and write FLAC](https://recursiveai.org/oneaudio/cookbook/flac/) and [Encode Opus](https://recursiveai.org/oneaudio/cookbook/encode-opus/).

When a managed library can replace FFmpeg, with ffmpeg commands mapped to C#: [Audio in .NET without FFmpeg](https://recursiveai.org/oneaudio/articles/audio-without-ffmpeg-dotnet/).