通过PHP / cURL发送Base64数据会导致语音转文本仅返回一个空的json字符串？

Question

I'm trying to send a Base64 string to Google's Speech-to-Text API in PHP. For annoying reasons I can't use composer to get the PHP library, so I'm trying to use the Speech to Text API through cURL.

$file = base64_encode( file_get_contents(__DIR__.'/test.ogg') );
$data = array(
  'config' => array(
    "encoding" => 'OGG_OPUS',
    'sampleRateHertz' => 16000,
    "languageCode"=> "en-GB"
  ),
  "audio"=> array (
    "content"=> $file
  )
);

$ch = curl_init("https://speech.googleapis.com/v1/speech:recognize?key=AIzaSyBxxxxxxxxxxxxxxxxxxxx-xxxxxxxxxxx");

curl_setopt_array($ch, array(
    CURLOPT_POST => 1,
    CURLOPT_POSTFIELDS => json_encode($data),
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_TIMEOUT => 10,
    CURLOPT_HTTPHEADER => array(
        "Content-Type: application/json"
    )
));
$json = curl_exec($ch);

What I know:

• The test.ogg is a valid Ogg/Opus file.
• The API key is correct
• Using a sample file in audio->uri works fine.

So, a simple question, I hope - what am I doing wrong?

Answer 1

I took your exact code and ran it myself with PHP 7.1, and I got an invalid key error back from the API. This suggests that the code itself is working fine and that it is related to your system, your network or some configurations.

Some suggestions of what you could look into;

• Do you have the curl extension installed and configured correctly?
• Can you access the API outside of PHP, for example via Paw or Postman ?
• Have you tried testing this code on another machine, and on another network?

Answer 2

Okay. Turns out that the Google API is really picky about Ogg Opus files. Running the file through ffmpeg to convert it to flac sorts it out.

Which is all a bit odd. Chrome (Google) creates a webm (Google) opus file which the Speech-to-text system (Google) can't handle. Convert it to the Ogg Opus file the API claims it can handle, and it fails silently. Convert that Ogg Opus to a flac file (so, from lossy to lossless, which is mental) and it suddenly works. And works incredibly well.

Or anyone else stumbling on this in the future, the ffmpeg command was

ffmpeg -i input.ogg -b:a 16000 output.flac

That sets it to 16000 bps, but I can't for the life of me remember what the :a does.