USB Camera, Microphone and Speaker API for Tessel 2
- Camera, for still shots (video coming soon)
- Microphone, for sound recording (coming soon)
- Player, for sound playback
- Speaker, for text-to-speech playback
npm install tessel-av
The Camera class produces instances that may be used to capture a still frame or stream frames from a capable USB camera.
| Property | Type | Value/Description | Default | Required |
|---|---|---|---|---|
| width | number | Set the width of the captured or streamed frames. | 320 | no |
| height | number | Set the height of the captured or streamed frames. | 240 | no |
| path | string | The system path to the video device | /dev/video0 |
no |
| quality | number | Set the quality from 0...1 | 1 | no |
| output | string | Name of an output file to direct still frame capture data. By default, no captures are written to disc. Setting output results in pipe: false |
/tmp/capture.jpg |
no |
captureTake a still frame. Returns aCaptureStreamof jpeg encoded data.streamCapture a stream of frames. Returns aCaptureStreamof jpeg encoded frame data.
datawhen capture has data.endedwhen capture ends.
Use the data event to capture a single frame and save it as a JPEG:
var fs = require('fs');
var path = require('path');
var av = require('tessel-av');
var camera = new av.Camera();
var 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():
var fs = require("fs");
var os = require("os");
var http = require("http");
var port = 8080;
var av = require("tessel-av");
var camera = new av.Camera({
width: 640,
height: 480,
});
var 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());Next, an example of streaming video frames to the browser from an Express + Socket.IO server:
var express = require('express');
var app = express();
var server = require('http').Server(app);
var io = require('socket.io')(server);
var os = require('os');
var path = require('path');
var cp = require('child_process');
var port = 8080;
var av = require('tessel-av');
server.listen(port, function () {
console.log(`http://${os.hostname()}.local:${port}`);
});
app.use(express.static(path.join(__dirname, '/public')));
io.on('connection', (socket) => {
var camera = new av.Camera();
socket.on('ready', () => camera.stream());
camera.on('data', (data) => {
socket.emit('image', data.toString('base64'));
});
});
process.on("SIGINT", _ => server.close());And here's the public/index.html file:
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>stream</title>
<script src="/socket.io/socket.io.js"></script>
</head>
<body>
<canvas id="output" width="320" height="240" style="border:solid;"></canvas>
<script>
window.onload = function() {
var context = document.getElementById("output").getContext("2d");
var socket = io();
var frame = null;
socket.on("image", (encoded) => {
frame = "data:image/jpeg;base64," + encoded;
});
socket.emit("ready");
setInterval(() => {
if (frame) {
var image = new Image();
image.src = frame;
try {
context.drawImage(image, 0, 0);
} catch (e) {
// ... suppress InvalidStateError
}
}
}, 1000 / 24);
};
</script>
</body>
</html>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)
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 (callingplay()will start the playback from the beginning.)
| Format | Type |
|---|---|
hh:mm:ss |
string |
ssss.dddd |
number |
ssss |
number |
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,
});endedwhen playback ends.playafterplay()is called.pauseafterpause()is called.stopafterstop()is called.timeupdateapproximately every 100ms. Delivers an approximation of the playback time in seconds, asssss.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.
var path = require('path');
var av = require('tessel-av');
var mp3 = path.join(__dirname, '20-second-nonsense.mp3');
var 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:
var path = require('path');
var av = require('./lib/index');
var mp3 = path.join(__dirname, 'some-audio-file.mp3');
var 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
.tesselincludefile. For example, to ensure thesong.mp3file is deployed to your Tessel 2, you'll create a file called.tesselincludethat contains the following:song.mp3You 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.tesselincludefile and listing that assets directory like this:public
(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.
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,
});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.
endedwhen speech ends.emptywhen speech ends and the speech queue is empty.lastwordwhen speech ends and the speech queue is empty and the program should prevent any furtheremptyevents from being emitted. This allows your robot to get the last word in without repeating themselves forever.sayaftersay()is called.stopafterstop()is called.timeupdateapproximately every 100ms. Delivers an approximation of the speech time in seconds, asssss.ddd.
The following is an example of the API and events working together:
- The first phrase will be said.
- Once spoken, the
endedevent will trigger, which will start the "cycle" through the letters of the alphabet.
var os = require('os');
var path = require('path');
var av = require('tessel-av');
var alphabet = 'abcdefghijklmnopqrstuvwxyz'.split('');
var 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":
var os = require('os');
var av = require('tessel-av');
var alphabet = 'abcdefghijklmnopqrstuvwxyz'.split('');
var 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');
});MIT.