2016-09-28 04:11

Google Speech API“请求中的采样率与FLAC标头不匹配”

  • php
  • ffmpeg

I'm trying to convert an mp4 video clip into a FLAC audio file and then have google speech spit out the words from the video so that I can detect if specific words were said.

I have everything working except that I am getting an error from the Speech API:

  "error": {
    "code": 400,
    "message": "Sample rate in request does not match FLAC header.",
    "status": "INVALID_ARGUMENT"

I am using FFMPEG in order to convert the mp4 into a FLAC file. I am specifying that the FLAC file be 16 bits in the command, but when I right click on the FLAC file Windows is telling me it is 302kbps.

Here is my PHP code:

// convert mp4 video to 16 bit flac audio file
$cmd = 'C:/wamp/www/ffmpeg/bin/ffmpeg.exe -i C:/wamp/www/test.mp4 -c:a flac -sample_fmt s16 C:/wamp/www/test.flac';
exec($cmd, $output);

// convert flac to text so we can detect if certain words were said
$data = array(
    "config" => array(
        "encoding" => "FLAC",
        "sampleRate" => 16000,
        "languageCode" => "en-US"
    "audio" => array(
        "content" => base64_encode(file_get_contents("test.flac")),

$json_data = json_encode($data);

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, 'https://speech.googleapis.com/v1beta1/speech:syncrecognize?key=MY_API_KEY');
curl_setopt($ch, CURLOPT_HTTPHEADER, array("Content-Type: application/json"));
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, $json_data);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);

$result = curl_exec($ch);
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