Google Storage and Big files - google-cloud-platform

Question

I'm using Google Cloud Functions and bucket triggers to :
Push Video on Cloud Storage bucket
Extract audio from video file with ffmpeg and store it locally
Save the audio to another bucket
Extract the text from the audio
Save it on another bucket
Translate the txt file automatically
Everything is doing fine if the file is under 5MB, but after the file is never uploaded to the other bucket. I have tried to upload it on the same bucket I get the video from but no use.
I have checked the google storage nodejs code and the code is doing a stream automatically after 5Mb of upload but it never ends.
Somebody have already this issue ?
My code is doing :
// Imports the Google Cloud client library
const storage = require('#google-cloud/storage')();
const ffmpegPath = require('#ffmpeg-installer/ffmpeg').path
const ffmpeg = require('fluent-ffmpeg');
const path = require('path');
const fs = require('fs');
const rimraf = require('rimraf'); // rimraf directly
// Binaries for ffmpeg
ffmpeg.setFfmpegPath(ffmpegPath);
/**
* Triggered from a message on a Cloud Storage bucket.
*
* #param {!Object} event The Cloud Functions event.
* #param {!Function} The callback function.
*/
exports.processFile = function(event, callback) {
console.log(JSON.stringify(event));
console.log('Processing file: ' + event.data.name);
const bucket = storage.bucket(event.data.bucket);
const bucketAudio = storage.bucket('distant-bucket');
const videoFile = bucket.file(event.data.name);
const destination = '/tmp/' + path.basename( event.data.name );
return new Promise((resolve, reject) => { return videoFile.download({
destination: destination
}).then((error) => {
if (error.length > 0) {
reject(error);
} else {
resolve(destination);
}
})
})
.then((fileinfo) => {
const filename = destination.replace( '.mp4', '.flac' );
return new Promise((resolve, reject) => {
ffmpeg(fileinfo)
.videoBitrate(19200)
.inputOptions('-vn')
.format('flac')
.audioChannels(1)
.audioBitrate(44100)
.output(filename)
.on('end', function() {
console.log('extracted audio : '+event.data.name+" to "+filename);
resolve(filename);
})
.on('error', function(err, stdout, stderr) {
reject(err);
})
.run()
});
})
.then((flacOutput) => {
console.log('save file '+flacOutput);
const stats = fs.statSync(flacOutput)
console.log(stats.size / 1000000.0);
// TODO: upload FLAC file to Cloud Storage
return bucket
.upload( flacOutput ).catch((err) => {
console.error('Failed to upload flac.', err);
return Promise.reject(err);
});
}).then(() => {
console.log(`Audio uploaded.`);
// Delete the temporary file.
return new Promise((resolve, reject) => {
fs.unlink(destination);
fs.unlink(destination.replace( '.mp4', '.flac' ), (err) => {
if (err) {
reject(err);
} else {
resolve();
}
});
});
});
};