Hello,
I would like ask you how works the FLV Metadata, i use it in order to analyse video streaming websites such as YouTube.
It analyses the video header only or the whole video?
<?php
class FLVMetaData {
private $buffer;
private $metaData;
public $fileName;
private $typeFlagsAudio;
private $typeFlagsVideo;
public $VCidMap = array(
2=>"Sorenson H.264",
3=>"Screen Video",
4=>"VP6",
5=>"VP6 with Alpha channel",
); //Video Codec ID(s)
public $ACidMap = array(
"Linear PCM, platform endian",
"ADPCM",
"MP3",
"Linear PCM, little endian",
"Nellymoser 16-kHz Mono",
"Nellymoser 8-kHz Mono",
"Nellymoser",
"G.711 A-law logarithmic PCM",
"G.711 mu-law logarithmic PCM",
"reserved",
"AAC",
"Speex",
14=>"MP3 8-Khz",
15=>"Device-specific sound"
); //Audio Codec ID(s)
/**
* CONSTRUCTOR : initialize class members
*
* @param string $flv : flv file path
*/
public function __construct($flv) {
$this->fileName = $flv;
$this->metaData = array(
"duration"=>null,
"size"=>null,
"framerate"=>null,
"width"=>null,
"height"=>null,
"videodatarate"=>null,
"audiodatarate"=>null,
"audiodelay"=>null,
"audiosamplesize"=>null,
"audiosamplerate"=>null,
"audiocodecid"=>null,
"videocodecid"=>null,
"version"=>null,
"headersize"=>0
);
}
/**
* Dumps Metadata of FLV
*/
public function dumpMetaData(){
echo "FLV Version: <strong>".$this->metaData["version"]."</strong><br />";
echo "Duration : <strong>".$this->metaData["duration"]."</strong> Second(s) <br />";
echo "File Size: <strong>".number_format(($this->metaData["size"]/pow(1024,2)) , 2)."</strong> MB<br />";
echo "Width: <strong>".$this->metaData["width"]."</strong> Pixel(s)<br />";
echo "Height: <strong>".$this->metaData["height"]."</strong> Pixel(s)<br />";
echo "Framerate: <strong>".number_format($this->metaData["framerate"],2)."</strong> FPS<br />";
echo "Video Data Rate: <strong>".number_format($this->metaData["videodatarate"])."</strong> Kbps<br />";
echo "Audio Data Rate: <strong>".number_format($this->metaData["audiodatarate"])."</strong> Kbps<br />";
echo "Audio Delay: <strong>".$this->metaData["audiodelay"]."</strong> Second(s)<br />";
echo "Audio Codec ID: <strong>".$this->metaData["audiocodecid"]."</strong><br />";
if(is_numeric($this->metaData["audiocodecid"])){
echo "Audio Format: <strong>".$this->ACidMap[$this->metaData["audiocodecid"]]."</strong><br />";
}
echo "Video Codec ID: <strong>".$this->metaData["videocodecid"]."</strong><br />";
if(is_numeric($this->metaData["videocodecid"])){
echo "Video Format: <strong>".$this->VCidMap[$this->metaData["videocodecid"]]."</strong><br />";
}
echo "Header Size: <strong>".$this->metaData["headersize"]."</strong> Byte(s)<br />";
}
/**
* Gets metadata of FLV file
*
* @return array $this->metaData : matadata of FLV
*/
public function getMetaData(){
if(!file_exists($this->fileName)){
echo "Error! {$this->fileName} does not exist.<br />";
return false;
}
if(!is_readable($this->fileName)){
echo "Error! Could not read the file. Check the file permissions.<br />";
return false;
}
$f = @fopen($this->fileName,"rb");
if(!$f){
echo "Try again to submit the file.<br />";
return;
}
$signature = fread($f,3);
if($signature != "FLV"){
echo "Error! Wrong file format.<br />";
// return false;
}
$this->metaData["version"] = ord(fread($f,1));
$this->metaData["size"] = filesize($this->fileName);
$flags = ord(fread($f,1));
$flags = sprintf("%'04b", $flags);
$this->typeFlagsAudio = substr($flags, 1, 1);
$this->typeFlagsVideo = substr($flags, 3, 1);
for ($i=0; $i < 4; $i++) {
$this->metaData["headersize"] += ord(fread($f,1)) ;
}
$this->buffer = fread($f, 400);
fclose($f);
if(strpos($this->buffer, "onMetaData") === false){
echo "Error! No MetaData Exists, try different file.<br />";
//return false;
}
foreach($this->metaData as $k=>$v){
$this->parseBuffer($k);
}
return $this->metaData;
}
/**
* Takes a field name of metadata, retrieve it's value and set it in $this->metaData
*
* @param string $fieldName : matadata field name
*/
private function parseBuffer($fieldName){
$fieldPos = strpos($this->buffer, $fieldName); //get the field position
if($fieldPos !== false){
$pos = $fieldPos + strlen($fieldName) + 1;
$buffer = substr($this->buffer,$pos);
$d = "";
for($i=0; $i < 8;$i++){
$d .= sprintf("%08b", ord(substr($buffer,$i,1)));
}
$total = self::bin2Double($d);
$this->metaData[$fieldName] = $total;
}
}
/**
* Calculates double-precision value of given binary string
* (IEEE Standard 754 - Floating Point Numbers)
*
* @param string binary data $strBin
* @return Float calculated double-precision number
*/
public static function bin2Double($strBin){
$sb = substr($strBin, 0, 1); // first bit is sign bit
$exponent = substr($strBin, 1, 11); // 11 bits exponent
$fraction = "1".substr($strBin, 12, 52); //52 bits fraction (1.F)
$s = pow(-1, bindec($sb));
$dec = pow(2, (bindec($exponent) - 1023)); //Decode exponent
if($dec == 2047){
if($fraction == 0){
if($s==0){
echo "Infinity";
}else{
echo "-Infinity";
}
}else{
echo "NaN";
}
}
if($dec > 0 && $dec < 2047){
$t = 1;
for($i=1 ; $i <= 53; $i++){
$t += ((int)substr($fraction, $i, 1)) * pow(2, -$i); //decode significand
}
$total = $s * $t * $dec ;
return $total;
}
return false;
}
}Thanks in advance,
Newcountry
