Google cloud -speech api return null result - php

Question

I work with Google cloud speech API. When I run my script there is a call to the API and a response. The operation info returns data, but the result is empty.
Here is my code (where file url, file name, key url, project name and bucket name I deleted the real data):
function __construct(){
$file_url='file path.mp3';
$filename='file name.mp3';
/** Create google client **/
$client = new Google_Client();
$key='path to google key';
putenv($key);
$client->useApplicationDefaultCredentials();
/** Create storage **/
$str_config = array(
'projectId' => 'project id'
);
$storage = new StorageClient($str_config);
$bucket_name='bucket name';
$bucket=$storage->bucket($bucket_name);
$object = $bucket->object($filename);
/** Create Speech **/
$config = array(
'projectId' => 'project id',
'languageCode' => 'en-US'
);
$options = array(
"encoding"=>'LINEAR16',
"languageCode"=>"en-US",
'sampleRateHertz' => 16000
)
;
$speech = new Google\Cloud\Speech\SpeechClient($config);
$operation = $speech->beginRecognizeOperation(
$object,
$options
);
$backoff = new ExponentialBackoff(100);
$backoff->execute(function () use ($operation) {
print('Waiting for operation to complete' . PHP_EOL);
$operation->reload();
if (!$operation->isComplete()) {
throw new Exception('Job has not yet completed', 500);
}
});
if ($operation->isComplete()) {
if (empty($results = $operation->results())) {
$results = $operation->info();
}
var_dump($results, $operatimon->results());
}
}
The result i get call:
Array
(
[0] => Array
(
[name] => some name
[metadata] => Array
(
[#type]=> type.googleapis.com/google.cloud.speech.v1.LongRunningRecognizeMetadata
[progressPercent] => 100
[startTime] => 2017-07-16T19:15:58.768490Z
[lastUpdateTime] => 2017-07-16T19:15:59.999625Z
)
[done] => 1
[response] => Array
(
[#type]=> type.googleapis.com/google.cloud.speech.v1.LongRunningRecognizeResponse
[totalBilledTime] => 15s
)
)
[1] => Array
(
)
)
I tried several file type whit several encodings, can't find the right combination. Or maybe there is another problem. Pleas Help.

Answer 1

Solved it by using the ffmpeg library to encode the audio to flac whit mono channel.

Answer 2

For anyone else encountering this problem, the issue could lie in your audio file not matching the encoding you've entered in your option array.
Check this resource:
https://cloud.google.com/speech-to-text/docs/reference/rest/v1beta1/RecognitionConfig#AudioEncoding
Just like the accepted answer, by changing from "LINEAR16" to "FLAC" and converting my audio file to FLAC, it worked for me.