Crate codec2

Codec 2 is an open source (LGPL 2.1) low bit rate speech codec.

This is a zero dependencies pure rust port of the original http://rowetel.com/codec2.html Currently 3200 and 2400 bitrates encoding and decoding are implemented.

Basic Usage

Create a Codec2 object e.g. Codec2::new(Codec2Mode::MODE_3200) then repeatedly obtain raw 8khz 16-bit audio samples and call encode to encode blocks of samples_per_frame() samples into bits_per_frame() compressed bits, in order. On the receiving end, create a Codec2 object and repeatedly call decode to decompress each chunk of received bytes into the next samples.

Complete example below. This example uses zerocopy to interpret the &[i16] slices as &[u8] for I/O.

Cargo.toml:

[dependencies]
zerocopy = "0.3.0"
codec2 = "0"

main.rs:

use codec2::*;
use std::env::args;
use std::io::prelude::*;
use zerocopy::AsBytes;

fn main() -> std::io::Result<()> {
    if args().len() != 4 || (args().nth(1).unwrap() != "enc" && args().nth(1).unwrap() != "dec") {
        eprintln!("Usage: {} (enc|dec) inputfile outputfilename", args().nth(0).unwrap());
        eprintln!("Files should be raw 16-bit signed 8khz audio");
        return Ok(());
    }
    let mut fin = std::fs::File::open(args().nth(2).unwrap())?;
    let mut fout = std::fs::File::create(args().nth(3).unwrap())?;
    let mut c2 = Codec2::new(Codec2Mode::MODE_3200);
    let mut samps = vec![0; c2.samples_per_frame()]; //u16 I/O buffer
    let mut packed = vec![0; (c2.bits_per_frame() + 7) / 8]; //u8 I/O buffer for encoded bits
    if args().nth(1).unwrap() == "enc" {
        while fin.read_exact(samps.as_bytes_mut()).is_ok() {
            c2.encode(&mut packed, &samps[..]);
            fout.write_all(&packed)?;
        }
    } else {
        while fin.read_exact(&mut packed).is_ok() {
            c2.decode(&mut samps[..], &packed);
            fout.write_all(samps.as_bytes())?;
        }
    }
    Ok(())
}

Structs

Codec2

A Codec2 object for encoding or decoding audio

Enums

Codec2Mode

Codec mode (bitrate). Currently only MODE_3200 and MODE_2400 are implemented