README.template

# forced-alignment-tools

A collection of links and notes on forced alignment tools

* Version: 1.0.7
* Date: 2017-03-04
* Author: [Alberto Pettarin](http://www.albertopettarin.it/) ([contact](http://www.albertopettarin.it/contact.html))
* License: [Creative Commons Attribution 4.0 International (CC BY 4.0)](https://creativecommons.org/licenses/by/4.0/legalcode)

Did I miss an aligner? Please open an issue or directly fork-commit-pullrequest.

## Definition of Forced Alignment

Given an audio file containing speech,
and the corresponding transcript,
computing a **forced alignment** is the process of
determining, for each fragment of the transcript,
the **time interval** (in the audio file)
containing the spoken text of the fragment.

A text fragment can have arbitrary granularity:

* a paragraph,
* a sentence,
* a portion of a sentence (i.e., a group of words),
* a word, or
* a phoneme (i.e., a single sound).

For example, given
[this text file](https://raw.githubusercontent.com/readbeyond/aeneas/master/aeneas/tests/res/container/job/assets/p001.xhtml)
and
[this audio file](https://raw.githubusercontent.com/readbeyond/aeneas/master/aeneas/tests/res/container/job/assets/p001.mp3),
a force aligment at verse-level can be the following:

```
1                                                     => [00:00:00.000, 00:00:02.640]
From fairest creatures we desire increase,            => [00:00:02.640, 00:00:05.880]
That thereby beauty's rose might never die,           => [00:00:05.880, 00:00:09.240]
But as the riper should by time decease,              => [00:00:09.240, 00:00:11.920]
His tender heir might bear his memory:                => [00:00:11.920, 00:00:15.280]
...
Pity the world, or else this glutton be,              => [00:00:43.640, 00:00:48.080]
To eat the world's due, by the grave and thee.        => [00:00:48.080, 00:00:53.240]
```

Typical **applications** of forced alignment include
[Audio-eBooks](https://www.readbeyond.it/audioebooks.html),
[closed captioning](https://en.wikipedia.org/wiki/Closed_captioning),
and automating the creation of training data
for automated speech recognition systems.


## Programs and Libraries

The following matrix contains **open source** programs and libraries
for computing forced alignments
that have been actually **proven to install and run**
(albeit the installation procedure for some of them is pretty complex).

All tools, except **aeneas**, are based on speech recognition algorithms;
all tools, except **aeneas** and **gentle**,
are maintained by research groups or individuals in academia.

Most tools are based on the [HTK](http://htk.eng.cam.ac.uk/),
which is not free for commercial purposes,
although a commercial license can be purchased
from the University of Cambridge.

You can also download the [raw data file in JSON format](data.json).

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## Additional Pointers

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