Wav to Flac file encoding

[Goringo]

Hello.

I am trying to do a little thing for practice. So, I'm trying to send POST request to google speech recognizer. I have a .wave file that is encoded to .flac with FLACFileEncoder with following code

FLAC_FileEncoder encoder = new FLAC_FileEncoder();
encoder.encode(new File("test.wav"), new File("test.flac"));

But google won't accept it and i don't know why. BUT if I use some kind of online converters(http://www.freefileconvert.com/ for example), it's OK.
Where I did wrong? Thanks for the help.