lab-rs

Toolkit and library for reading, writing, and manipulating HTK .lab label files

.lab files are plain-text label files used by HTK and throughout speech and singing-voice tooling for phoneme/word alignments. Each line is a labelled time segment, with times in units of 100 nanoseconds:

0 2500000 sil
2500000 4200000 hh
4200000 6100000 eh
6100000 7800000 l
7800000 9200000 ow
9200000 12000000 sil

The parser handles the common subset of the HTK label format tolerantly: start and end times are optional, an optional numeric score may follow the label text, and blank lines and extra whitespace are ignored. Quoted text with \\ escapes is supported and is emitted when needed to preserve ambiguous label text, normalized end-only labels use an empty quoted start marker ("" <end> <text>).

I tried my best not to make my code look AI-generated since that's apparently something you need to worry about nowadays. Excuse the potential lack of comments and documentation outside this README and docs.rs. And yes, I am bitter about this.

Library

cargo add lab-rs

The library has no dependencies by default. Enable the serde feature for Serialize/Deserialize on all types.

use lab_rs::LabFile;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut lab = LabFile::from_path("hello.lab")?;

    println!("{} labels", lab.len());
    lab.retain(|l| l.text != "sil");
    lab.shift_secs(0.1);
    lab.save("hello-edited.lab")?;

    Ok(())
}

LabFile dereferences to Vec<Label>, so the usual vector and slice methods work directly. It also provides helpers for looking up labels by time, shifting and scaling timestamps, merging adjacent labels, and validating a label sequence. See the documentation for the full interface.

CLI

cargo install lab-rs --features cli

This installs a lab binary that lets you do things like:

lab info hello.lab              # label count, duration, unique labels, sanity checks
lab cat hello.lab               # print with times in seconds (--raw for 100ns units)
lab convert hello.lab --to json # also: tsv, audacity, lab
lab shift hello.lab -- -0.25    # shift all times by -0.25 s (stdout, or -i for in place)
lab scale hello.lab 2.0         # stretch all times by 2x
lab merge hello.lab             # merge consecutive identical labels

License

MIT, see LICENSE.