wip on MP3
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1 changed files with 207 additions and 5 deletions
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@ -394,10 +394,203 @@ function extractFragmentedMP4( $filename ) {
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return $segments;
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}
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function consolidate( $target, $segments ) {
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$out = [
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'init' => $segments['init'],
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// http://www.mp3-tech.org/programmer/frame_header.html
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class MP3FrameHeader {
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private $header;
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public $valid = false;
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public $size = 0;
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public $sync;
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public $mpeg;
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public $layer;
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public $protection;
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public $bitrate;
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public $sampleRate;
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public $padding;
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private static $bits = [
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'sync' => [ 21, 11 ],
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'mpeg' => [ 19, 2 ],
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'layer' => [ 17, 2 ],
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'protection' => [ 16, 1 ],
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'bitrate' => [ 12, 4 ],
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'sampleRate' => [ 10, 2 ],
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'padding' => [ 9, 1 ],
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'private' => [ 8, 1 ], // not needed below this
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'channelMode' => [ 6, 2 ],
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'modeExt' => [ 4, 2 ],
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'copyright' => [ 3, 1 ],
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'original' => [ 2, 1 ],
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'emphasis' => [ 0, 2 ],
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];
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private const SYNC_MASK = 0x7ff;
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// 1s used for reserved slots to avoid exploding
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// in case of invalid input
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private static $sampleRates = [
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// MPEG-2.5
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[ 11025, 12000, 8000, 1 ],
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// Reserved
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[ 1, 1, 1, 1 ],
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// MPEG-2
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[ 22050, 24000, 16000, 1 ],
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// MPEG-1
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[ 44100, 48000, 32000, 1 ],
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];
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private static $bitrates = [
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[
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// MPEG-2
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// invalid
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[ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, ],
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// layer 3
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[ 0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0 ],
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// layer 2
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[ 0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0 ],
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// layer 1
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[ 0, 32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224, 256, 0 ],
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],
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[
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// MPEG-1
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// invalid
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[ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, ],
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// layer 3
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[ 0, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 192, 224, 256, 320, 0 ],
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// layer 2
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[ 0, 32, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 384, 0 ],
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// layer 1
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[ 0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384, 316, 448, 0 ],
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]
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];
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private function field( $name ) {
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[ $shift, $bits ] = self::$bits[$name];
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$mask = ( 1 << $bits ) - 1;
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return ( $this->header >> $shift ) & $mask;
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}
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public function __construct( $header ) {
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$this->header = $header;
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$this->sync = $this->field( 'sync' ) == self::SYNC_MASK;
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if ( $this->sync ) {
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$this->mpeg = $this->field( 'mpeg' );
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$this->layer = $this->field( 'layer' );
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$this->protection = $this->field( 'protection' );
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$br = $this->field( 'bitrate' );
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$this->bitrate = 1000 * self::$bitrates[$this->mpeg & 1][$this->layer][$br];
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$sr = $this->field( 'sampleRate' );
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$this->sampleRate = self::$sampleRates[$this->mpeg][$sr];
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$this->padding = $this->field( 'padding' );
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$this->valid = $this->sync;
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if ( $this->bitrate == 0 ) {
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var_dump( $this );
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echo "br: $br\n";
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//throw new Exception( "Invalid bitrate" );
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$this->valid = false;
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}
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if ( $this->sampleRate == 1 ) {
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var_dump( $this );
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echo "sr: $sr\n";
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//throw new Exception( "Invalid sample rate" );
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$this->valid = false;
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}
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$this->size = intval( 144.0 * $this->bitrate / $this->sampleRate );
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if ( $this->protection ) {
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$this->size += 2;
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}
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if ( $this->padding ) {
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$this->size++;
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}
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}
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}
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}
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class MP3Reader {
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private $file;
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public function __construct( $file ) {
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$this->file = $file;
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}
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public function pos() {
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return ftell( $this->file );
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}
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public function readFrame() {
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while ( true ) {
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// Look for the sync pattern
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$start = $this->pos();
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$bytes = fread( $this->file, 4 );
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if ( $bytes === false || strlen( $bytes ) < 4 ) {
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// end of file
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return false;
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}
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$data = unpack( "Nval", $bytes );
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$header = new MP3FrameHeader( $data['val'] );
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if ( $header->valid ) {
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// Note we don't need the data at this time.
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//fseek( $this->file, $start + $header->size, SEEK_SET );
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var_dump ( $header );
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fread( $this->file, $header->size - 4 );
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return $header;
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}
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$x = hexdump( $bytes );
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print "BACKUP $x\n";
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if ( $header->sync && !$header->valid ) {
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$x = hexdump( $bytes );
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die('xxx ' . $x);
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}
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// back up 3 bytes and try again
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fseek( $this->file, $start + 1, SEEK_SET );
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}
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}
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}
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function extractMP3( $filename ) {
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$file = fopen( $filename, 'rb' );
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if ( !$file ) {
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throw new Exception( 'Error opening MP3 file' );
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}
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try {
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$reader = new MP3Reader( $file );
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$segments = [];
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$timestamp = 0.0;
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while ( true ) {
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$start = $reader->pos();
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$frame = $reader->readFrame();
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if ( !$frame ) {
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return $segments;
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}
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$duration = 144.0 / $frame->sampleRate;
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$segments[] = [
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'start' => $start,
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'size' => $frame->size,
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'timestamp' => $timestamp,
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'duration' => $duration,
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];
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$timestamp += $duration;
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}
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} finally {
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fclose( $file );
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}
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}
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function consolidate( $target, $segments ) {
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$out = [];
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if ( isset( $segments['init'] ) ) {
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$out['init'] = $segments['init'];
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}
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$n = count( $segments ) - 1;
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$start = $segments[0]['start'];
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$size = $segments[0]['size'];
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@ -492,8 +685,17 @@ function playlist( $filename, $segments ) {
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$argv = $_SERVER['argv'];
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$self = array_shift( $argv );
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$filename = array_shift( $argv );
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$segments = extractFragmentedMP4( $filename );
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$segments = consolidate( 10, $segments );
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$target = 10;
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$ext = substr( $filename, strrpos( $filename, '.' ) );
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if ( $ext === '.mp3' ) {
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$segments = extractMP3( $filename );
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} elseif ( $ext === '.mp4' ) {
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$segments = extractFragmentedMP4( $filename );
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} else {
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die( "Unexpected file extension $ext\n" );
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}
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$segments = consolidate( $target, $segments );
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/*
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foreach ( $segments as $key => $segment ) {
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