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<?php
// +----------------------------------------------------------------------+
// | PHP version 5 |
// +----------------------------------------------------------------------+
// | Copyright (c) 2002-2006 James Heinrich, Allan Hansen |
// +----------------------------------------------------------------------+
// | This source file is subject to version 2 of the GPL license, |
// | that is bundled with this package in the file license.txt and is |
// | available through the world-wide-web at the following url: |
// | http://www.gnu.org/copyleft/gpl.html |
// +----------------------------------------------------------------------+
// | getID3() - http://getid3.sourceforge.net or http://www.getid3.org |
// +----------------------------------------------------------------------+
// | Authors: James Heinrich <info�getid3*org> |
// | Allan Hansen <ah�artemis*dk> |
// +----------------------------------------------------------------------+
// | module.audio.aac_adts.php |
// | Module for analyzing AAC files with ADTS header. |
// | dependencies: NONE |
// +----------------------------------------------------------------------+
//
// $Id: module.audio.aac_adts.php,v 1.4 2006/11/02 10:48:01 ah Exp $
class getid3_aac_adts extends getid3_handler
{
public $option_max_frames_to_scan = 1000000;
public $option_return_extended_info = false;
private $decbin_cache;
private $bitrate_cache;
public function __construct(getID3 $getid3) {
parent::__construct($getid3);
// Populate bindec_cache
for ($i = 0; $i < 256; $i++) {
$this->decbin_cache[chr($i)] = str_pad(decbin($i), 8, '0', STR_PAD_LEFT);
}
// Init cache
$this->bitrate_cache = array ();
// Fast scanning?
if (!$getid3->option_accurate_results) {
$this->option_max_frames_to_scan = 200;
$getid3->warning('option_accurate_results set to false - bitrate and playing time are not accurate.');
}
}
public function Analyze() {
$getid3 = $this->getid3;
// based loosely on code from AACfile by Jurgen Faul <jfaul�gmx.de>
// http://jfaul.de/atl or http://j-faul.virtualave.net/atl/atl.html
// http://faac.sourceforge.net/wiki/index.php?page=ADTS
// * ADTS Fixed Header: these don't change from frame to frame
// syncword 12 always: '111111111111'
// ID 1 0: MPEG-4, 1: MPEG-2
// layer 2 always: '00'
// protection_absent 1
// profile 2
// sampling_frequency_index 4
// private_bit 1
// channel_configuration 3
// original/copy 1
// home 1
// emphasis 2 only if ID == 0 (ie MPEG-4)
// * ADTS Variable Header: these can change from frame to frame
// copyright_identification_bit 1
// copyright_identification_start 1
// aac_frame_length 13 length of the frame including header (in bytes)
// adts_buffer_fullness 11 0x7FF indicates VBR
// no_raw_data_blocks_in_frame 2
// * ADTS Error check
// crc_check 16 only if protection_absent == 0
$getid3->info['aac']['header'] = array () ;
$info_aac = &$getid3->info['aac'];
$info_aac_header = & $info_aac['header'];
$byte_offset = $frame_number = 0;
while (true) {
// Breaks out when end-of-file encountered, or invalid data found,
// or MaxFramesToScan frames have been scanned
fseek($getid3->fp, $byte_offset, SEEK_SET);
// First get substring
$sub_string = fread($getid3->fp, 10);
$sub_string_length = strlen($sub_string);
if ($sub_string_length != 10) {
throw new getid3_exception('Failed to read 10 bytes at offset '.(ftell($getid3->fp) - $sub_string_length).' (only read '.$sub_string_length.' bytes)');
}
// Initialise $aac_header_bitstream
$aac_header_bitstream = '';
// Loop thru substring chars
for ($i = 0; $i < 10; $i++) {
$aac_header_bitstream .= $this->decbin_cache[$sub_string[$i]];
}
$sync_test = bindec(substr($aac_header_bitstream, 0, 12));
$bit_offset = 12;
if ($sync_test != 0x0FFF) {
throw new getid3_exception('Synch pattern (0x0FFF) not found at offset '.(ftell($getid3->fp) - 10).' (found 0x0'.strtoupper(dechex($sync_test)).' instead)');
}
// Only gather info once - this takes time to do 1000 times!
if ($frame_number > 0) {
// MPEG-4: 20, // MPEG-2: 18
$bit_offset += $aac_header_bitstream[$bit_offset] ? 18 : 20;
}
// Gather info for first frame only - this takes time to do 1000 times!
else {
$info_aac['header_type'] = 'ADTS';
$info_aac_header['synch'] = $sync_test;
$getid3->info['fileformat'] = 'aac';
$getid3->info['audio']['dataformat'] = 'aac';
$info_aac_header['mpeg_version'] = $aac_header_bitstream{$bit_offset++} == '0' ? 4 : 2;
$info_aac_header['layer'] = bindec(substr($aac_header_bitstream, $bit_offset, 2));
$bit_offset += 2;
if ($info_aac_header['layer'] != 0) {
throw new getid3_exception('Layer error - expected 0x00, found 0x'.dechex($info_aac_header['layer']).' instead');
}
$info_aac_header['crc_present'] = $aac_header_bitstream{$bit_offset++} == '0' ? true : false;
$info_aac_header['profile_id'] = bindec(substr($aac_header_bitstream, $bit_offset, 2));
$bit_offset += 2;
$info_aac_header['profile_text'] = getid3_aac_adts::AACprofileLookup($info_aac_header['profile_id'], $info_aac_header['mpeg_version']);
$info_aac_header['sample_frequency_index'] = bindec(substr($aac_header_bitstream, $bit_offset, 4));
$bit_offset += 4;
$info_aac_header['sample_frequency'] = getid3_aac_adts::AACsampleRateLookup($info_aac_header['sample_frequency_index']);
$getid3->info['audio']['sample_rate'] = $info_aac_header['sample_frequency'];
$info_aac_header['private'] = $aac_header_bitstream{$bit_offset++} == 1;
$info_aac_header['channel_configuration'] = $getid3->info['audio']['channels'] = bindec(substr($aac_header_bitstream, $bit_offset, 3));
$bit_offset += 3;
$info_aac_header['original'] = $aac_header_bitstream{$bit_offset++} == 1;
$info_aac_header['home'] = $aac_header_bitstream{$bit_offset++} == 1;
if ($info_aac_header['mpeg_version'] == 4) {
$info_aac_header['emphasis'] = bindec(substr($aac_header_bitstream, $bit_offset, 2));
$bit_offset += 2;
}
if ($this->option_return_extended_info) {
$info_aac[$frame_number]['copyright_id_bit'] = $aac_header_bitstream{$bit_offset++} == 1;
$info_aac[$frame_number]['copyright_id_start'] = $aac_header_bitstream{$bit_offset++} == 1;
} else {
$bit_offset += 2;
}
}
$frame_length = bindec(substr($aac_header_bitstream, $bit_offset, 13));
if (!isset($this->bitrate_cache[$frame_length])) {
$this->bitrate_cache[$frame_length] = ($info_aac_header['sample_frequency'] / 1024) * $frame_length * 8;
}
@$info_aac['bitrate_distribution'][$this->bitrate_cache[$frame_length]]++;
$info_aac[$frame_number]['aac_frame_length'] = $frame_length;
$bit_offset += 13;
$info_aac[$frame_number]['adts_buffer_fullness'] = bindec(substr($aac_header_bitstream, $bit_offset, 11));
$bit_offset += 11;
$getid3->info['audio']['bitrate_mode'] = ($info_aac[$frame_number]['adts_buffer_fullness'] == 0x07FF) ? 'vbr' : 'cbr';
$info_aac[$frame_number]['num_raw_data_blocks'] = bindec(substr($aac_header_bitstream, $bit_offset, 2));
$bit_offset += 2;
if ($info_aac_header['crc_present']) {
$bit_offset += 16;
}
if (!$this->option_return_extended_info) {
unset($info_aac[$frame_number]);
}
$byte_offset += $frame_length;
if ((++$frame_number < $this->option_max_frames_to_scan) && (($byte_offset + 10) < $getid3->info['avdataend'])) {
// keep scanning
} else {
$info_aac['frames'] = $frame_number;
$getid3->info['playtime_seconds'] = ($getid3->info['avdataend'] / $byte_offset) * (($frame_number * 1024) / $info_aac_header['sample_frequency']); // (1 / % of file scanned) * (samples / (samples/sec)) = seconds
$getid3->info['audio']['bitrate'] = (($getid3->info['avdataend'] - $getid3->info['avdataoffset']) * 8) / $getid3->info['playtime_seconds'];
ksort($info_aac['bitrate_distribution']);
$getid3->info['audio']['encoder_options'] = $info_aac['header_type'].' '.$info_aac_header['profile_text'];
return true;
}
}
}
public static function AACsampleRateLookup($samplerate_id) {
static $lookup = array (
0 => 96000,
1 => 88200,
2 => 64000,
3 => 48000,
4 => 44100,
5 => 32000,
6 => 24000,
7 => 22050,
8 => 16000,
9 => 12000,
10 => 11025,
11 => 8000,
12 => 0,
13 => 0,
14 => 0,
15 => 0
);
return (isset($lookup[$samplerate_id]) ? $lookup[$samplerate_id] : 'invalid');
}
public static function AACprofileLookup($profile_id, $mpeg_version) {
static $lookup = array (
2 => array (
0 => 'Main profile',
1 => 'Low Complexity profile (LC)',
2 => 'Scalable Sample Rate profile (SSR)',
3 => '(reserved)'
),
4 => array (
0 => 'AAC_MAIN',
1 => 'AAC_LC',
2 => 'AAC_SSR',
3 => 'AAC_LTP'
)
);
return (isset($lookup[$mpeg_version][$profile_id]) ? $lookup[$mpeg_version][$profile_id] : 'invalid');
}
}
?>
|
