How SoundCloud stream their mp3 files? - nginx

Question

Im trying to implement same method to play .mp3 files with JwPlayer on my webiste like SoundCloud has.
I have a large mp3 files which sometime have 4 hours length. So I don't want to load it as one source file in JwPlayer.
I see soundcloud stream thier mp3 files in partial (160k pices). How they do that?
I try configure my nginx to
location /uploads/ {
mp4;
mp4_buffer_size 160k;
mp4_max_buffer_size 200k;
}
But it does not working. Mp3 still load in a one big request.
I try option 2 read file manualy by php script like
if (isset($_SERVER['HTTP_RANGE'])) {
$c_start = $start;
$c_end = $end;
list(, $range) = explode('=', $_SERVER['HTTP_RANGE'], 2);
if (strpos($range, ',') !== false) {
header('HTTP/1.1 416 Requested Range Not Satisfiable');
header("Content-Range: bytes $start-$end/$size");
exit;
}
if ($range == '0-') {
$c_start = 0;
}
else {
$range = explode('-', $range);
$c_start = (int)$range[0];
if($c_start > 2407200) {
exit;
}
$c_end = (isset($range[1]) && is_numeric($range[1])) ? $range[1] : $c_start + $end;
}
$c_end = ($c_end > $size) ? $size : $c_end;
if ($c_start > $c_end || $c_start > $size - 1 || $c_end >= $size) {
header('HTTP/1.1 416 Requested Range Not Satisfiable');
header("Content-Range: bytes $start-$end/$size");
exit;
}
$start = $c_start;
$end = $c_end;
$length = $end - $start + 1; // Calculate new content length
fseek($fp, $start);
header('HTTP/1.1 206 Partial Content');
}
header("Content-Range: bytes $start-$end/$size");
header("Content-Length: $length");
$buffer = 1024 * 8;
while(!feof($fp) && ($p = ftell($fp)) <= $end) {
if ($p + $buffer > $end) {
$buffer = $end - $p + 1;
}
set_time_limit(0); // Reset time limit for big files
echo fread($fp, $buffer);
flush(); // Free up memory. Otherwise large files will trigger PHP's memory limit.
}
fclose($fp);
It's not bad, but when I STOP playing mp3 the script load other pieces of file.
So how SoundCloud do this? When play music they load music in small pieces and when stop player the request stop too.