Google Speech API duplicates responses - php

Question

I am using Speech API v2 with PHP, here is a code:
$file_to_upload = array('myfile'=>'#'.$filename.'.flac');
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "https://www.google.com/speech-api/v2/recognize?output=json&lang=ru-RU&key=___my_api_key___");
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_HTTPHEADER, array("Content-Type: audio/x-flac; rate=8000"));
curl_setopt($ch, CURLOPT_POSTFIELDS, $file_to_upload);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$result=curl_exec ($ch);
Google responses with two JSON objects, first is empty, second has valid response as I expect. That causes difficulties in parsing and further processing. See HTTP dump:
My POST request:
POST /speech-api/v2/recognize?output=json&lang=ru-RU&key=___my_api_key___ HTTP/1.1
Host: www.google.com
Accept: */*
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/34.0.1847.131 Safari/537.36
Content-Length: 13123
Expect: 100-continue
Content-Type: audio/x-flac; rate=8000; boundary=----------------------------9641e899ac92
------------------------------9641e899ac92
Content-Disposition: form-data; name="myfile"; filename="/tmp/voice/1400157667.6440-in.wav.flac"
Content-Type: application/octet-stream
fLaC..."......e..\......! ..{..!y>..7..............................( ...reference libFLAC 1.2.1 20070917.
...encoded binary data...
------------------------------9641e899ac92--
Response with duplicate result of recognition:
HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8
Content-Disposition: attachment
Cache-Control: no-transform
X-Content-Type-Options: nosniff
Pragma: no-cache
Date: Thu, 15 May 2014 12:41:09 GMT
Server: S3 v1.0
X-XSS-Protection: 1; mode=block
X-Frame-Options: SAMEORIGIN
Alternate-Protocol: 80:quic
Transfer-Encoding: chunked
e
{"result":[]} <--- first one
f8
{"result":[{"alternative":[{"transcript":"............","confidence":0.73531097},{"transcript":"................"},{"transcript":".............."},{"transcript":"................"},{"transcript":"............ .."}],"final":true}],"result_index":0} <--- second one
0
Why could it happen? When I used API v1, it had the only response. Other examples of v2 in the internet also have only one.
Thanks a lot.

Answer 1

First of all, be sure that the language you are using provides Speaker Diarization. For instance, for spanish in Colombia Google does not provide speaker diarization, but for spanish from Spain, it does:
Language Support
Besides, sometimes a slight alteration of audio is needed, what can be achieved using ffmpeg:
ffmpeg -i input.wav -ac 1 -ab 128k -filter:a volume=0.9 -filter:a equalizer=f=4000:t=h:w=200:g=-2 output.wav