phpからmp3ファイルの情報を取得するクラス

転載元：http://www.zedwood.com/article/127/php-calculate-duration-of-mp3

```php:mp3file|use

<?php

require_once('mp3file.php');

$f = 'somefile.mp3';
$m = new mp3file($f);
$a = $m->get_metadata();

if ($a['Encoding']=='Unknown')
    echo "?";
else if ($a['Encoding']=='VBR')
    print_r($a);
else if ($a['Encoding']=='CBR')
    print_r($a);
unset($a);
?>

```


```php:mp3file

<?php
/*
php5 class (will not work in php4)
for detecting bitrate and duration of regular mp3 files (not VBR files)
*/

//-----------------------------------------------------------------------------
class mp3file
{
    protected $block;
    protected $blockpos;
    protected $blockmax;
    protected $blocksize;
    protected $fd;
    protected $bitpos;
    protected $mp3data;
    public function __construct($filename)
    {
        $this->powarr  = array(0=>1,1=>2,2=>4,3=>8,4=>16,5=>32,6=>64,7=>128);
        $this->blockmax= 1024;
       
        $this->mp3data = array();
        $this->mp3data['Filesize'] = filesize($filename);

        $this->fd = fopen($filename,'rb');
        $this->prefetchblock();
        $this->readmp3frame();
    }
    public function __destruct()
    {
        fclose($this->fd);
    }
    //-------------------
    public function get_metadata()
    {
        return $this->mp3data;
    }
    protected function readmp3frame()
    {
        $iscbrmp3=true;
        if ($this->startswithid3())
            $this->skipid3tag();
        else if ($this->containsvbrxing())
        {
            $this->mp3data['Encoding'] = 'VBR';
            $iscbrmp3=false;
        }
        else if ($this->startswithpk())
        {
            $this->mp3data['Encoding'] = 'Unknown';
            $iscbrmp3=false;
        }
   
        if ($iscbrmp3)
        {
            $i = 0;
            $max=5000;
            //look in 5000 bytes...
            //the largest framesize is 4609bytes(256kbps@8000Hz  mp3)
            for($i=0; $i<$max; $i++)
            {
                //looking for 1111 1111 111 (frame synchronization bits)                
                if ($this->getnextbyte()==0xFF)
                    if ($this->getnextbit() && $this->getnextbit() && $this->getnextbit())
                        break;
            }
            if ($i==$max)
                $iscbrmp3=false;
        }
   
        if ($iscbrmp3)
        {
            $this->mp3data['Encoding'         ] = 'CBR';
            $this->mp3data['MPEG version'     ] = $this->getnextbits(2);
            $this->mp3data['Layer Description'] = $this->getnextbits(2);
            $this->mp3data['Protection Bit'   ] = $this->getnextbits(1);
            $this->mp3data['Bitrate Index'    ] = $this->getnextbits(4);
            $this->mp3data['Sampling Freq Idx'] = $this->getnextbits(2);
            $this->mp3data['Padding Bit'      ] = $this->getnextbits(1);
            $this->mp3data['Private Bit'      ] = $this->getnextbits(1);
            $this->mp3data['Channel Mode'     ] = $this->getnextbits(2);
            $this->mp3data['Mode Extension'   ] = $this->getnextbits(2);
            $this->mp3data['Copyright'        ] = $this->getnextbits(1);
            $this->mp3data['Original Media'   ] = $this->getnextbits(1);
            $this->mp3data['Emphasis'         ] = $this->getnextbits(1);
            $this->mp3data['Bitrate'          ] = mp3file::bitratelookup($this->mp3data);
            $this->mp3data['Sampling Rate'    ] = mp3file::samplelookup($this->mp3data);
            $this->mp3data['Frame Size'       ] = mp3file::getframesize($this->mp3data);
            $this->mp3data['Length'           ] = mp3file::getduration($this->mp3data,$this->tell2());
            $this->mp3data['Length mm:ss'     ] = mp3file::seconds_to_mmss($this->mp3data['Length']);
           
            if ($this->mp3data['Bitrate'      ]=='bad'     ||
                $this->mp3data['Bitrate'      ]=='free'    ||
                $this->mp3data['Sampling Rate']=='unknown' ||
                $this->mp3data['Frame Size'   ]=='unknown' ||
                $this->mp3data['Length'     ]=='unknown')
            $this->mp3data = array('Filesize'=>$this->mp3data['Filesize'], 'Encoding'=>'Unknown');
        }
        else
        {
            if(!isset($this->mp3data['Encoding']))
                $this->mp3data['Encoding'] = 'Unknown';
        }
    }
    protected function tell()
    {
        return ftell($this->fd);
    }
    protected function tell2()
    {
        return ftell($this->fd)-$this->blockmax +$this->blockpos-1;
    }
    protected function startswithid3()
    {
        return ($this->block[1]==73 && //I
                $this->block[2]==68 && //D
                $this->block[3]==51);  //3
    }
    protected function startswithpk()
    {
        return ($this->block[1]==80 && //P
                $this->block[2]==75);  //K
    }
    protected function containsvbrxing()
    {
        //echo "<!--".$this->block[37]." ".$this->block[38]."-->";
        //echo "<!--".$this->block[39]." ".$this->block[40]."-->";
        return(
               ($this->block[37]==88  && //X 0x58
                $this->block[38]==105 && //i 0x69
                $this->block[39]==110 && //n 0x6E
                $this->block[40]==103)   //g 0x67
/*               ||
               ($this->block[21]==88  && //X 0x58
                $this->block[22]==105 && //i 0x69
                $this->block[23]==110 && //n 0x6E
                $this->block[24]==103)   //g 0x67*/
              );  

    }
    protected function debugbytes()
    {
        for($j=0; $j<10; $j++)
        {
            for($i=0; $i<8; $i++)
            {
                if ($i==4) echo " ";
                echo $this->getnextbit();
            }
            echo "<BR>";
        }
    }
    protected function prefetchblock()
    {
        $block = fread($this->fd, $this->blockmax);
        $this->blocksize = strlen($block);
        $this->block = unpack("C*", $block);
        $this->blockpos=0;
    }
    protected function skipid3tag()
    {
        $bits=$this->getnextbits(24);//ID3
        $bits.=$this->getnextbits(24);//v.v flags

        //3 bytes 1 version byte 2 byte flags
        $arr = array();
        $arr['ID3v2 Major version'] = bindec(substr($bits,24,8));
        $arr['ID3v2 Minor version'] = bindec(substr($bits,32,8));
        $arr['ID3v2 flags'        ] = bindec(substr($bits,40,8));
        if (substr($bits,40,1)) $arr['Unsynchronisation']=true;
        if (substr($bits,41,1)) $arr['Extended header']=true;
        if (substr($bits,42,1)) $arr['Experimental indicator']=true;
        if (substr($bits,43,1)) $arr['Footer present']=true;

        $size = "";
        for($i=0; $i<4; $i++)
        {
            $this->getnextbit();//skip this bit, should be 0
            $size.= $this->getnextbits(7);
        }

        $arr['ID3v2 Tags Size']=bindec($size);//now the size is in bytes;
        if ($arr['ID3v2 Tags Size'] - $this->blockmax>0)
        {
            fseek($this->fd, $arr['ID3v2 Tags Size']+10 );
            $this->prefetchblock();
            if (isset($arr['Footer present']) && $arr['Footer present'])
            {
                for($i=0; $i<10; $i++)
                    $this->getnextbyte();//10 footer bytes
            }
        }
        else
        {
            for($i=0; $i<$arr['ID3v2 Tags Size']; $i++)
                $this->getnextbyte();
        }
    }

    protected function getnextbit()
    {
        if ($this->bitpos==8)
            return false;

        $b=0;
        $whichbit = 7-$this->bitpos;
        $mult = $this->powarr[$whichbit]; //$mult = pow(2,7-$this->pos);
        $b = $this->block[$this->blockpos+1] & $mult;
        $b = $b >> $whichbit;
        $this->bitpos++;

        if ($this->bitpos==8)
        {
            $this->blockpos++;
               
            if ($this->blockpos==$this->blockmax) //end of block reached
            {
                $this->prefetchblock();
            }
            else if ($this->blockpos==$this->blocksize)
            {//end of short block reached (shorter than blockmax)
                return;//eof
            }
           
            $this->bitpos=0;
        }
        return $b;
    }
    protected function getnextbits($n=1)
    {
        $b="";
        for($i=0; $i<$n; $i++)
            $b.=$this->getnextbit();
        return $b;
    }
    protected function getnextbyte()
    {
        if ($this->blockpos>=$this->blocksize)
            return;

        $this->bitpos=0;
        $b=$this->block[$this->blockpos+1];
        $this->blockpos++;
        return $b;
    }
    //-----------------------------------------------------------------------------
    public static function is_layer1(&$mp3) { return ($mp3['Layer Description']=='11'); }
    public static function is_layer2(&$mp3) { return ($mp3['Layer Description']=='10'); }
    public static function is_layer3(&$mp3) { return ($mp3['Layer Description']=='01'); }
    public static function is_mpeg10(&$mp3)  { return ($mp3['MPEG version']=='11'); }
    public static function is_mpeg20(&$mp3)  { return ($mp3['MPEG version']=='10'); }
    public static function is_mpeg25(&$mp3)  { return ($mp3['MPEG version']=='00'); }
    public static function is_mpeg20or25(&$mp3)  { return ($mp3['MPEG version']{1}=='0'); }
    //-----------------------------------------------------------------------------
    public static function bitratelookup(&$mp3)
    {
        //bits               V1,L1  V1,L2  V1,L3  V2,L1  V2,L2&L3
        $array = array();
        $array['0000']=array('free','free','free','free','free');
        $array['0001']=array(  '32',  '32',  '32',  '32',   '8');
        $array['0010']=array(  '64',  '48',  '40',  '48',  '16');
        $array['0011']=array(  '96',  '56',  '48',  '56',  '24');
        $array['0100']=array( '128',  '64',  '56',  '64',  '32');
        $array['0101']=array( '160',  '80',  '64',  '80',  '40');
        $array['0110']=array( '192',  '96',  '80',  '96',  '48');
        $array['0111']=array( '224', '112',  '96', '112',  '56');
        $array['1000']=array( '256', '128', '112', '128',  '64');
        $array['1001']=array( '288', '160', '128', '144',  '80');
        $array['1010']=array( '320', '192', '160', '160',  '96');
        $array['1011']=array( '352', '224', '192', '176', '112');
        $array['1100']=array( '384', '256', '224', '192', '128');
        $array['1101']=array( '416', '320', '256', '224', '144');
        $array['1110']=array( '448', '384', '320', '256', '160');
        $array['1111']=array( 'bad', 'bad', 'bad', 'bad', 'bad');
       
        $whichcolumn=-1;
        if      (mp3file::is_mpeg10($mp3) && mp3file::is_layer1($mp3) )//V1,L1
            $whichcolumn=0;
        else if (mp3file::is_mpeg10($mp3) && mp3file::is_layer2($mp3) )//V1,L2
            $whichcolumn=1;
        else if (mp3file::is_mpeg10($mp3) && mp3file::is_layer3($mp3) )//V1,L3
            $whichcolumn=2;
        else if (mp3file::is_mpeg20or25($mp3) && mp3file::is_layer1($mp3) )//V2,L1
            $whichcolumn=3;
        else if (mp3file::is_mpeg20or25($mp3) && (mp3file::is_layer2($mp3) || mp3file::is_layer3($mp3)) )
            $whichcolumn=4;//V2,   L2||L3
       
        if (isset($array[$mp3['Bitrate Index']][$whichcolumn]))
            return $array[$mp3['Bitrate Index']][$whichcolumn];
        else
            return "bad";
    }
    //-----------------------------------------------------------------------------
    public static function samplelookup(&$mp3)
    {
        //bits               MPEG1   MPEG2   MPEG2.5
        $array = array();
        $array['00'] =array('44100','22050','11025');
        $array['01'] =array('48000','24000','12000');
        $array['10'] =array('32000','16000','8000');
        $array['11'] =array('res','res','res');
       
        $whichcolumn=-1;
        if      (mp3file::is_mpeg10($mp3))
            $whichcolumn=0;
        else if (mp3file::is_mpeg20($mp3))
            $whichcolumn=1;
        else if (mp3file::is_mpeg25($mp3))
            $whichcolumn=2;
       
        if (isset($array[$mp3['Sampling Freq Idx']][$whichcolumn]))
            return $array[$mp3['Sampling Freq Idx']][$whichcolumn];
        else
            return 'unknown';
    }
    //-----------------------------------------------------------------------------
    public static function getframesize(&$mp3)
    {
        if ($mp3['Sampling Rate']>0)
        {
            return  ceil((144 * $mp3['Bitrate']*1000)/$mp3['Sampling Rate']) + $mp3['Padding Bit'];
        }
        return 'unknown';
    }
    //-----------------------------------------------------------------------------
    public static function getduration(&$mp3,$startat)
    {
        if ($mp3['Bitrate']>0)
        {
            $KBps = ($mp3['Bitrate']*1000)/8;
            $datasize = ($mp3['Filesize'] - ($startat/8));
            $length = $datasize / $KBps;
            return sprintf("%d", $length);
        }
        return "unknown";
    }
    //-----------------------------------------------------------------------------
    public static function seconds_to_mmss($duration)
    {
        return sprintf("%d:%02d", ($duration /60), $duration %60 );
    }
}
?>

```