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tessel-av

tessel-av

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USB Camera, Microphone, MP3 Player and Text Speaker support for Tessel 2.

This module does not and will not support the Tessel 1 Camera Module

  • Camera, for capturing video streams and still shots
  • Microphone, for sound streaming
  • Player, for sound playback
  • Speaker, for text-to-speech playback
npm install tessel-av

av.Camera

The Camera class produces instances that may be used to capture a still frame or stream frames from a capable USB camera.

av.Camera Initialization

Property Type Value/Description Default Required
device string The system path to the video device /dev/video0 no
dimensions string Valid "WxH" dimensions. Is limited to dimensions supported by the device.* "800x600" no
fps number Frames per second. Will be ignored if value is unsupported. Per camera no
port number Port number for the video server 8080 no
quality number Set the quality from 0...1 1 no
fps number Frames per second. Will be ignored if value is unsupported. Per camera no

* The device itself determines what dimensions are supported. Since the output comes directly from the camera hardware, invalid dimensions will be overridden by device if not supported.

  • capture Take a still frame. Returns a CaptureStream, call pipe with a destination to send a frame of jpeg encoded data.
  • stream Stream mjpg frames from camera.

av.Camera Events

  • data when stream has data.
  • frame when camera has a complete frame.

av.Camera Examples

Use the data event to capture a single frame and save it as a JPEG:

'use strict';
const fs = require('fs');
const path = require('path');
 
const av = require('tessel-av');
const camera = new av.Camera();
const capture = camera.capture();
 
capture.on('data', function(data) {
  fs.writeFile(path.join(__dirname, 'captures/captured-via-data-event.jpg'), data);
});

Respond to an HTTP request by piping the stream returned by capture():

'use strict';
const fs = require('fs');
const os = require('os');
const http = require('http');
const port = 8888;
 
const av = require('tessel-av');
const camera = new av.Camera({
  width: 320,
  height: 240,
});
 
const server = http.createServer((request, response) => {
  response.writeHead(200, { "Content-Type": "image/jpg" });
 
  camera.capture().pipe(response);
 
}).listen(port, () => console.log(`http://${os.hostname()}.local:${port}`));
 
process.on("SIGINT", _ => server.close());

A very simple example of direct-to-browser streaming:

'use strict';
const express = require('express');
const app = express();
const server = require('http').Server(app);
const os = require('os');
const path = require('path');
const port = 8888;
 
const av = require('tessel-av');
const camera = new av.Camera();
 
server.listen(port, function () {
  console.log(`http://${os.hostname()}.local:${port}`);
});
 
app.use(express.static(path.join(__dirname, '/public')));
app.get('/stream', (request, response) => {
  response.redirect(camera.url);
});

And here's the public/index.html file, which should be referenced in a .tesselinclude file):

<!doctype html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <title>streaming video to img element</title>
  </head>
  <body>
    <img src="/stream">
  </body>
</html>

av.Player

The Player class produces instances that may be used to play audio from an mp3 file stored on the Tessel 2.

(Prior to v0.3.0, the av.Speaker class was used for audio file playback, and while that still works in versions >=0.3.0, programs will need to update to use this class before 1.0.0 (estimated release: July 1st, 2016)

av.Player Initialization

The Player class constructor accepts one argument, which is optional, that specifies an mp3 file to play when the play() method is called. The may be omitted and supplied directly to play(file [, time]) at a later time in the object's lifecycle.

  • play([seconds]) Play the specified file. Optionally provide a time to start at in seconds. See Allowed Time String Formats

  • play([ file [, seconds]) Play the specified file. Optionally provide a time to start at in seconds. See Allowed Time String Formats

  • play([ 'file.mp3', ...options ]) Play the file with additional options in an array.

  • play(options) Play the file with additional options in an object.

    Options {
      phrase: "Hello Dave, you're looking well today", 
      ...
    }
    
  • pause() Pause playback of the current file.

  • stop() Stop playback of the current file (calling play() will start the playback from the beginning.)

Allowed Time String Formats

Format Type
hh:mm:ss string
ssss.dddd number
ssss number

Options

Options may be most of options supported by madplay. For example, if I wanted to set the amplitude and pitch:

player.play(['foo.mp3', '-a', 10, '-r', 2 ]);
player.play(['foo.mp3', 'a', 10, 'r', 2 ]);

or

player.play({
  file: 'foo.mp3',
  a: 10,
  r: 2,
});

av.Player Events

  • ended when playback ends.
  • play after play() is called.
  • pause after pause() is called.
  • stop after stop() is called.
  • timeupdate approximately every 100ms. Delivers an approximation of the playback time in seconds, as ssss.ddd.

The following is an example of the API and events working together:

  • The sound will play from the beginning
  • After approximate 2 seconds, the sound will pause
  • After 1 second pause, sound will resume , it will resume playback from the 10 second mark, play until just after the 12 second mark, where it will stop and then play from the beginning again.
'use strict';
const path = require('path');
const av = require('tessel-av');
const mp3 = path.join(__dirname, '20-second-nonsense.mp3');
const sound = new av.Player(mp3);
 
sound.play();
 
sound.on('timeupdate', function(seconds) {
  seconds = Math.round(seconds);
 
  if (seconds === 2) {
    this.pause();
  }
 
  if (seconds > 12) {
    this.stop().play();
  }
});
 
sound.on('pause', function() {
  setTimeout(() => this.play(10), 1000);
});

Alternatively, an mp3 file may be provided at the play(...) call site:

'use strict';
const path = require('path');
const av = require('./lib/index');
const mp3 = path.join(__dirname, 'some-audio-file.mp3');
const sound = new av.Player();
 
// Play the mp3, starting at the 10 second mark. 
sound.play(mp3, "10");
 
sound.on('ended', function() {
  console.log('This is not the end!');
  sound.play();
});

Remember that you must explicitly specify static assets by listing them in a .tesselinclude file file. For example, to ensure the song.mp3 file is deployed to your Tessel 2, you'll create a file called .tesselinclude that contains the following:

song.mp3

You may find it easier to put all static assets in a sub-directory, such as public/, or similar. Then you can include all files and sub-directories by creating a .tesselinclude file and listing that assets directory like this:

public

av.Speaker

(Prior to v0.3.0, the av.Speaker class was used for audio file playback, and while that still works in versions >=0.3.0, programs will need to update to use this class before 1.0.0 (estimated release: July 1st, 2016)

  • say("phrase") Speak the phrase (string).
  • say(["phrase", ...]) Speak the phrase with additional options in an array.
  • say(options) Speak the phrase with additional options in an object.
    Options {
      phrase: "Hello Dave, you're looking well today", 
      ...
    }
    
  • stop() Stop playback.

av.Speaker Initialization

Options may be most of the options supported by espeak. For example, if I wanted to set the amplitude and pitch:

speaker.say(['Hello!', '-a', 10, '-p', 50 ]);
speaker.say(['Hello!', 'a', 10, 'p', 50 ]);

or

speaker.say({
  phrase: 'Hello!',
  a: 10,
  p: 50,
});

Queuing

Back to back calls to speaker.say(...) will result in each phrase being queued. Once a phrase has been said, the next phrase in the queue will be spoken.

av.Speaker Events

  • ended when speech ends.
  • empty when speech ends and the speech queue is empty.
  • lastword when speech ends and the speech queue is empty and the program should prevent any further empty events from being emitted. This allows your robot to get the last word in without repeating themselves forever.
  • say after say() is called.
  • stop after stop() is called.
  • timeupdate approximately every 100ms. Delivers an approximation of the speech time in seconds, as ssss.ddd.

The following is an example of the API and events working together:

  • The first phrase will be said.
  • Once spoken, the ended event will trigger, which will start the "cycle" through the letters of the alphabet.
'use strict';
const os = require('os');
const path = require('path');
const av = require('tessel-av');
 
const alphabet = 'abcdefghijklmnopqrstuvwxyz'.split('');
const speaker = new av.Speaker();
 
speaker.say(`
  Hello, this is ${os.hostname()}
  I'm going to say my A-B-C's now
`);
 
speaker.on('ended', function() {
  if (alphabet.length) {
    this.say(alphabet.shift());
  }
});

Alternatively, each letter can be "queued":

'use strict';
const os = require('os');
const av = require('tessel-av');
 
const alphabet = 'abcdefghijklmnopqrstuvwxyz'.split('');
const speaker = new av.Speaker();
 
speaker.say(`
  Hello, this is ${os.hostname()}
  I'm going to say my A-B-C's now
`);
 
alphabet.forEach(letter => speaker.say(letter));
 
speaker.on('lastword', function() {
  // If this had been an `empty` event, it would've  
  // been emitted again as soon as the next phrase  
  // was spoken. 
  this.say('And now I know my A-B-Cs');
});

License

MIT.