Google Cloud语音识别API（PHP）-文件编码问题

Question

I am playing with google speech recognition API and have some trouble with file encoding.

Firstly, I tried the API using the Google's HTML form ( https://cloud.google.com/speech-to-text/ ) by file uploading a mp3. It worked nicely, so I have created a Google Cloud project and tried to do that by API using PHP. However, I can't get it to work, it always return empty response.

I am using Google's example code:

$projectId = 'xx';

# Instantiates a client
$speech = new SpeechClient([
    'projectId' => $projectId,
    'languageCode' => 'sk-SK',
]);

# The name of the audio file to transcribe
$fileName = 'D:\ts\all.mp3';

# The audio file's encoding and sample rate
$options = [
    'encoding' => 'LINEAR16',
    'model' => 'default',
    'sampleRateHertz' => 44100,
];

# Detects speech in the audio file
$results = $speech->recognize(fopen($fileName, 'r'), $options);

var_dump($results); // array(0)

foreach ($results as $result) {
    echo 'Transcription: ' . $result->alternatives()[0]['transcript'] . PHP_EOL;
}

When I looked deeper, I noticed, that when I am uploading the mp3 file through the browser, the same file is encoded differently than when using the API.

These are the first 615 characters of encoded audio data sent to API by browser (working):

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

And this is made by Google's PHP library (not working):

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

The Google's PHP library is using base64_encode method to format the request, but I don't know what type of encoding uses the browser.

When I modify the Google's PHP libraries and force the API to send the correct data (as was sent by browser), it works and I am getting correct results.

So the question is, why is the Google's example not working for me and how to correctly encode the file?

Answer 1

Solved, the file needs to be converted to WAV. It's probably happening by javascript when uploading the mp3 by form.