Using IBM Watson Text-to-Speech with Firebase Cloud Functions? - firebase

Question

I'm trying to use set up a Firebase Cloud Function to access IBM Watson Text-to-Speech. The problem is writing the returned audiofile to my Firestore database.
This test to return the list of voices worked, logging the response to the Functions log:
exports.test = functions.firestore.document('IBM_Watson_Token/Test_Value').onUpdate((change, context) => {
var textToSpeech = new TextToSpeechV1({
username: 'groucho',
password: 'swordfish'
});
return textToSpeech.listVoices(null, function(error, voices) {
if (error) {
console.log(error);
} else {
console.log(JSON.stringify(voices, null, 2));
}
});
});
Here is the documentation example Node code for returning an audiofile and writing it to the server:
var TextToSpeechV1 = require('watson-developer-cloud/text-to-speech/v1');
var fs = require('fs');
var textToSpeech = new TextToSpeechV1({
username: '{username}',
password: '{password}'
});
var synthesizeParams = {
text: 'Hello world',
accept: 'audio/wav',
voice: 'en-US_AllisonVoice'
};
// Pipe the synthesized text to a file.
textToSpeech.synthesize(synthesizeParams).on('error', function(error) {
console.log(error);
}).pipe(fs.createWriteStream('hello_world.wav'));
Firebase doesn't allow writing files to the server using fs, you have to write to a Firestore database. I changed the last line of the example code to write to Firestore, using a promise:
exports.test = functions.firestore.document('IBM_Watson_Token/Test_Value').onUpdate((change, context) => {
var textToSpeech = new TextToSpeechV1({
username: 'groucho',
password: 'swordfish'
});
var synthesizeParams = {
text: 'Hello world',
accept: 'audio/wav',
voice: 'en-US_AllisonVoice'
};
return textToSpeech.synthesize(synthesizeParams).on('error', function(error) {
console.log(error);
}).then(function (audiofile) {
admin.firestore().collection('IBM_Watson_Token').doc('hello_world').set({
'audiofile': audiofile
})
})
.catch(function (error) {
console.log(error);
});
});
The error message was
TypeError: textToSpeech.synthesize(...).on(...).then is not a function
How do I save the audiofile that comes back from Watson to Firestore?

Answer 1

That would be because the synthesize method is not returning a promise. You will need to use a callback construct that looks like
textToSpeech.synthesize(params, function (err, body, response) {
if (err) {
...
} else {
// body is the audio
...
}
});