module.audio.dss.php

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<?php
//  available at http://getid3.sourceforge.net                 //
//            or http://www.getid3.org                         //
//          also https://github.com/JamesHeinrich/getID3       //
// See readme.txt for more details                             //
//                                                             //
// module.audio.dss.php                                        //
// module for analyzing Digital Speech Standard (DSS) files    //
// dependencies: NONE                                          //
//                                                            ///


class getid3_dss extends getid3_handler
{

        public function Analyze() {
                $info = &$this->getid3->info;

                $this->fseek($info['avdataoffset']);
                $DSSheader  = $this->fread(1540);

                if (!preg_match('#^(\x02|\x03)ds[s2]#', $DSSheader)) {
                        $info['error'][] = 'Expecting "[02-03] 64 73 [73|32]" at offset '.$info['avdataoffset'].', found "'.getid3_lib::PrintHexBytes(substr($DSSheader, 0, 4)).'"';
                        return false;
                }

                // some structure information taken from http://cpansearch.perl.org/src/RGIBSON/Audio-DSS-0.02/lib/Audio/DSS.pm
                $info['encoding']              = 'ISO-8859-1'; // not certain, but assumed
                $info['dss'] = array();

                $info['fileformat']            = 'dss';
                $info['mime_type']             = 'audio/x-'.substr($DSSheader, 1, 3); // "audio/x-dss" or "audio/x-ds2"
                $info['audio']['dataformat']   =            substr($DSSheader, 1, 3); //         "dss" or         "ds2"
                $info['audio']['bitrate_mode'] = 'cbr';

                $info['dss']['version']           =                            ord(substr($DSSheader,    0,   1));
                $info['dss']['hardware']          =                           trim(substr($DSSheader,   12,  16)); // identification string for hardware used to create the file, e.g. "DPM 9600", "DS2400"
                $info['dss']['unknown1']          =   getid3_lib::LittleEndian2Int(substr($DSSheader,   28,   4));
                // 32-37 = "FE FF FE FF F7 FF" in all the sample files I've seen
                $info['dss']['date_create']       = $this->DSSdateStringToUnixDate(substr($DSSheader,   38,  12));
                $info['dss']['date_complete']     = $this->DSSdateStringToUnixDate(substr($DSSheader,   50,  12));
                $info['dss']['playtime_sec']      = intval((substr($DSSheader,  62, 2) * 3600) + (substr($DSSheader,  64, 2) * 60) + substr($DSSheader,  66, 2)); // approximate file playtime in HHMMSS
                $info['dss']['playtime_ms']       =   getid3_lib::LittleEndian2Int(substr($DSSheader,  512,   4)); // exact file playtime in milliseconds. Has also been observed at offset 530 in one sample file, with something else (unknown) at offset 512
                $info['dss']['priority']          =                            ord(substr($DSSheader,  793,   1));
                $info['dss']['comments']          =                           trim(substr($DSSheader,  798, 100));
                $info['dss']['sample_rate_index'] =                            ord(substr($DSSheader, 1538,   1));  // this isn't certain, this may or may not be where the sample rate info is stored, but it seems consistent on my small selection of sample files

                $info['audio']['bits_per_sample']  = 16; // maybe, maybe not -- most compressed audio formats don't have a fixed bits-per-sample value, but this is a reasonable approximation
                $info['audio']['sample_rate']      = $this->DSSsampleRateLookup($info['dss']['sample_rate_index']);
                $info['audio']['channels']         = 1;

                $info['playtime_seconds'] = $info['dss']['playtime_ms'] / 1000;
                if (floor($info['dss']['playtime_ms'] / 1000) != $info['dss']['playtime_sec']) {
                        // *should* just be playtime_ms / 1000 but at least one sample file has playtime_ms at offset 530 instead of offset 512, so safety check
                        $info['playtime_seconds'] = $info['dss']['playtime_sec'];
                        $this->getid3->warning('playtime_ms ('.number_format($info['dss']['playtime_ms'] / 1000, 3).') does not match playtime_sec ('.number_format($info['dss']['playtime_sec']).') - using playtime_sec value');
                }
                $info['audio']['bitrate'] = ($info['filesize'] * 8) / $info['playtime_seconds'];

                return true;
        }

        public function DSSdateStringToUnixDate($datestring) {
                $y = substr($datestring,  0, 2);
                $m = substr($datestring,  2, 2);
                $d = substr($datestring,  4, 2);
                $h = substr($datestring,  6, 2);
                $i = substr($datestring,  8, 2);
                $s = substr($datestring, 10, 2);
                $y += (($y < 95) ? 2000 : 1900);
                return mktime($h, $i, $s, $m, $d, $y);
        }

        public function DSSsampleRateLookup($sample_rate_index) {
                static $dssSampleRateLookup = array(
                        0x0A => 16000,
                        0x0C => 11025,
                        0x0D => 12000,
                        0x15 =>  8000,
                );
                if (!array_key_exists($sample_rate_index, $dssSampleRateLookup)) {
                        $this->getid3->warning('unknown sample_rate_index: '.$sample_rate_index);
                        return false;
                }
                return $dssSampleRateLookup[$sample_rate_index];
        }

}