功能是取得flv视频的时间,是网上找的,但是很多地方不明白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 $int_value;
}
//获得视频的数字时间
function getTime($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 $duration;
}
//转化为0:03:56的时间格式
function fn($time){
$num = $time;
$sec = intval($num/1000);
$h = intval($sec/3600);
$m = intval(($sec%3600)/60);
$s = intval(($sec%60));
$tm = $h.':'.$m.':'.$s;
return $tm;
}
$t = getTime("/tmp/907701336.flv");//显示数字时间如236722
echo fn($t);//显示时间格式0:03:56
对 BigEndian2Int这个函数看不懂,以及getTimes里面的一些数字 有什么意思?
$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 $int_value;
}
//获得视频的数字时间
function getTime($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 $duration;
}
//转化为0:03:56的时间格式
function fn($time){
$num = $time;
$sec = intval($num/1000);
$h = intval($sec/3600);
$m = intval(($sec%3600)/60);
$s = intval(($sec%60));
$tm = $h.':'.$m.':'.$s;
return $tm;
}
$t = getTime("/tmp/907701336.flv");//显示数字时间如236722
echo fn($t);//显示时间格式0:03:56
对 BigEndian2Int这个函数看不懂,以及getTimes里面的一些数字 有什么意思?
FLV包括文件头(File Header)和文件体(File Body)两部分,其中文件体由一系列的Tag及Tag Size对组成。Tag包括Tag Header和Tag Data两部分。
Tag Header 的
第5-7字节为UI24类型的值,表示该Tag的时间戳(单位为ms)
第8个字节为时间戳的扩展字节,当24位数值不够时,该字节作为最高位将时间戳扩展为32位值只要将这一系列的时间戳加起来就得到了整个播放时间UI24类型 占 3 个字节,高位在前
所以程序中有
$int_value += ord($byte_word{$i}) * pow(256, ($byte_wordlen - 1 - $i));
这个写法很烂,还用到了 pow
你也可以修改他,基础算式
令传入串 $s,有 ( ord($s{0}) * 256 + ord($s{1}) ) * 256 + ord($s{2})