wip on MP3

This commit is contained in:
Brooke Vibber 2023-03-03 11:36:12 -08:00
parent e8177c3d2d
commit 194b0fc284

View file

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