vtt-utils

vtt-utils is a library for handling VTT subtitles within voiceful. It includes different functions to import and parse subtitles, as well as to export them for voiceful in the appropriate format.

Install

npm i -S vtt-utils

Dependencies

node-webvtt (Voctro Labs fork)

Usage

Importing the library

var vttutils = require('vtt-utils');

API

srtToVtt(inputSrtText)

Generates a VTT-formatted subtitle from a SRT text

/**
 * @param  {String} inputSrtText Input subtitle text, in SRT format
 * @return {String}              Output subtitle text, in VTT format
 */

parseToSentences(inputVttText)

Parses an input subtitle provided as text and output the subtitle with sentence per cue. When several cues are joined into a single one, this function automatically adds <prosody duration> SSML tags to keep the original time info, in milliseconds (e.g. <prosody duration="1000ms"> for 1 second). When two non-adjacent cues are joined (i.e. the ending time of the first is not equal to the start time of the second), it adds SSML <break> SSML tags to keep this info (e.g. <break time="1000ms">) for cues separated by 1 second.

/**
* @param  {String} inputVttText Input subtitle text, in VTT format
* @return {String}              Output subtitle text, in VTT format
*/

checkSubtitlesEquivalency(srcVttText, targetVttText)

Checks that the start and end times of cues in two VTT subtitles are equal

/**
* @param  {String} srcVttText    Source subtitle text, in VTT format
* @param  {String} targetVttText Target subtitle text, in VTT format
* @return {Boolean}              True if both are equivalent, false otherwise
*/

assignStyleToCue(inputVttText, style, cueIdx)

Assigns a style to the cue in position cueIdx for the VTT-formatted subtitle inputVttText by adding a <emphasis level="style"> tag to the cue.

/**
 * @param  {String} inputVttText Input subtitle text, in VTT format
 * @param  {String} style        Name of the style for the cue (e.g: 'neutral', 'sad', 'aggresive'...)
 * @param  {Number} cueIdx       Index of the cue where the style must be applied
 * @return {String}              inputVttText modified
 */

getSpeakers(vttText)

Returns the different speakers present in the VTT formated subtitle vttText, looking at the voice (<v>) tags in the cues.

/**
 * @param  {String}     vttText Subtitle text, in VTT format
 * @return {String[]}           Array of speakers
 */

getAsJSON(language, modelsString, vttText)

Generates JSON-formatted to generate synthesis with voiceful.

/**
* @param  {String}  language        Language identifier
* @param  {String}  modelsString    Array with speakers-voice models-(optional)defaultStyle correspondence (e.g. '[["speaker1","model1","style1"],["speaker2","model2"]]')
* @param  {String}  vttText         Subtitle text, in VTT format
* @param  {Number[]}    selectedSentences   Array with indexes of sentences to be synthesized
* @return {String}                  JSON-formatted string for synthesis
*/

removeSpeaker(cueText)

Return the text of a cue without speaker tag

/**
 * @param  {String} cueText Text from a sentence of a subtitle
 * @return {String}              cueText without the speaker tag
 */

removeTags(cueText)

Return the text of a cue without any tags

/**
 * @param  {String} cueText Text from a sentence of a subtitle
 * @return {String}              cueText without tags
 */

generateNoiseGateString(vttText, transitionTime)

Return noise gate values as string to introduce in VoMix effect

/**
 * @param  {String} vttText Subtitle text, in VTT format
 * @param  {Number} transitionTime Transition time, in seconds
 * @return {String}              Noise gate values as string to introduce in JSON
 */

getNumberOfCues(vttText)

Returns the number of cues in the vtt subtitle vttText

/**
* @param  {String} vttText Subtitle text, in VTT format
* @return {Number}         Number of cues
*/

getVideoFriendlyVtt(vttText)

Returns the subtitle with cues short enough that they are readable together with video. It <prosody duration> tags are present, the function uses this information. Otherwise, it returns a subtitle with cues shorter than 70 characters.

/**
* @param   {String} vttText    Subtitle text, in VTT format
* @return  {String}            Video-friendly subtitle, in VTT format
*/

Development

To start developing first clone de repository and install the dependencies with NPM:

git clone [email protected]:VoctroLabs/vtt-utils.git
cd vtt-utils
npm install

Example

There is an example of usage in example/index.html. First run the following commands to produce the necessary bundle for the browser:

npm run build-example

Then open example/index.html in your browser.

Tests

Run tests with:

npm run test

License

MIT