用PHP读取flv文件的播放时间长度

<?php
// +----------------------------------------------------------------------+
// | php version 4&5 |
// +----------------------------------------------------------------------+
// | copyright (c) 2007 jackiewangjackieit@hotmail.com |
// +----------------------------------------------------------------------+
// | this source file's function is to get the time length of flv |
// | main function gettime param:$name the flv file you want to get |
// +----------------------------------------------------------------------+
function bigendian2int($byte_word, $signed = false) {
$int_value = 0;
$byte_wordlen = strlen($byte_word);
for ($i = 0; $i < $byte_wordlen; $i++) {
$int_value += ord($byte_word{$i}) * pow(256, ($byte_wordlen - 1 - $i));
}
if ($signed) {
$sign_mask_bit = 0x80 << (8 * ($byte_wordlen - 1));
if ($int_value & $sign_mask_bit) {
$int_value = 0 - ($int_value & ($sign_mask_bit - 1));
}
}
return $int_value;
}
function gettime($name){
if(!file_exists($name)){
return;
}
$flv_data_length=filesize($name);
$fp = @fopen($name, 'rb');
$flv_header = fread($fp, 5);
fseek($fp, 5, seek_set);
$frame_size_data_length =bigendian2int(fread($fp, 4));
$flv_header_frame_length = 9;
if ($frame_size_data_length > $flv_header_frame_length) {
fseek($fp, $frame_size_data_length - $flv_header_frame_length, seek_cur);
}
$duration = 0;
while ((ftell($fp) + 1) < $flv_data_length) {
$this_tag_header = fread($fp, 16);
$data_length = bigendian2int(substr($this_tag_header, 5, 3));
$timestamp = bigendian2int(substr($this_tag_header, 8, 3));
$next_offset = ftell($fp) - 1 + $data_length;
if ($timestamp > $duration) {
$duration = $timestamp;
}
fseek($fp, $next_offset, seek_set);
}
fclose($fp);
return $duration;
}
?>