DrAbc.SilkCodec

SilkCodec.NET

Pure .NET Silk v3 speech codec. It encodes 16-bit little-endian PCM and decodes #!SILK_V3 streams, including the Tencent/WeChat leading 0x02 marker.

This library is written in C#. It does not load native silkcodec binaries and is not a conversion of the Skype SILK C sources.

Install

dotnet add package DrAbc.SilkCodec

Target frameworks: net10.0, net8.0, net472.

Encode

var encoder = new SilkEncoder(new SilkEncoderOptions
{
    SampleRate = 24000,
    BitRate = 25000,
    Tencent = true
});

byte[] silk = encoder.Encode(File.ReadAllBytes("voice.pcm"));
encoder.Encode("voice.pcm", "voice.silk");

Decode

var decoder = new SilkDecoder(new SilkDecoderOptions
{
    SampleRate = 24000
});

byte[] pcm = decoder.Decode(File.ReadAllBytes("voice.silk"));
decoder.Decode("voice.silk", "voice.pcm");

Extensions

The core package encodes and decodes raw 16-bit little-endian PCM. Companion packages convert other audio formats through popular C# audio libraries. Each extension is a separate NuGet package.

dotnet add package DrAbc.SilkCodec.NAudio
dotnet add package DrAbc.SilkCodec.CSCore
dotnet add package DrAbc.SilkCodec.FFMpegCore

using SilkCodec.NET;
using SilkCodec.NET.NAudio;

var encoder = new SilkEncoder(new SilkEncoderOptions
{
    SampleRate = 24000,
    BitRate = 25000,
    Tencent = true
});

byte[] silk = encoder.EncodeFile("voice.mp3");
encoder.EncodeFile("voice.wav", "voice.silk");

var decoder = new SilkDecoder(new SilkDecoderOptions { SampleRate = 24000 });
decoder.DecodeFile("voice.silk", "voice.wav");
byte[] wav = decoder.DecodeToWav(silk);

.pcm, .raw and .s16le files are treated as signed 16-bit little-endian mono at the encoder or decoder sample rate.

CLI

The repository includes a small command-line tool. It is a separate executable and is not included in the NuGet package.

dotnet run --project src/SilkCodec.NET.Cli -- encode voice.pcm voice.silk --tencent
dotnet run --project src/SilkCodec.NET.Cli -- decode voice.silk voice.pcm

Useful options:

silkcodec encode <input.pcm> [output.silk] [-r 24000] [-b 25000] [-t]
silkcodec decode <input.silk> [output.pcm] [-r 24000]

If the output path is omitted, the input extension is changed to .silk or .pcm.

Encode and decode print elapsed time. To compare throughput against the test clips:

dotnet run --project src/SilkCodec.NET.Cli -c Release -- bench tests/SilkCodec.NET.Tests/assets

Compatibility

• Container: #!SILK_V3, optional Tencent 0x02 prefix, little-endian frame lengths, optional -1 terminator when not Tencent
• Payload: Silk SDK 1.0.9 / WeChat-QQ Silk v3 range-coded frames
• PCM: packed signed 16-bit little-endian, mono

The decoder reads existing Silk v3 files. The encoder emits a valid Silk v3 bitstream that this decoder (and other Silk v3 decoders) can play. Encoder output is not bit-identical to the Skype SDK.

License

MIT (Expat), see LICENSE.