source: extensions/charlies_content/getid3/getid3/module.audio.voc.php

<?php
/////////////////////////////////////////////////////////////////
/// getID3() by James Heinrich <info@getid3.org>               //
//  available at http://getid3.sourceforge.net                 //
//            or http://www.getid3.org                         //
/////////////////////////////////////////////////////////////////
// See readme.txt for more details                             //
/////////////////////////////////////////////////////////////////
//                                                             //
// module.audio.voc.php                                        //
// module for analyzing Creative VOC Audio files               //
// dependencies: NONE                                          //
//                                                            ///
/////////////////////////////////////////////////////////////////


class getid3_voc
{

        function getid3_voc(&$fd, &$ThisFileInfo) {

                $OriginalAVdataOffset = $ThisFileInfo['avdataoffset'];
                fseek($fd, $ThisFileInfo['avdataoffset'], SEEK_SET);
                $VOCheader  = fread($fd, 26);

                if (substr($VOCheader, 0, 19) != 'Creative Voice File') {
                        $ThisFileInfo['error'][] = 'Expecting "Creative Voice File" at offset '.$ThisFileInfo['avdataoffset'].', found "'.substr($VOCheader, 0, 19).'"';
                        return false;
                }

                // shortcuts
                $thisfile_audio = &$ThisFileInfo['audio'];
                $ThisFileInfo['voc'] = array();
                $thisfile_voc        = &$ThisFileInfo['voc'];

                $ThisFileInfo['fileformat']               = 'voc';
                $thisfile_audio['dataformat']      = 'voc';
                $thisfile_audio['bitrate_mode']    = 'cbr';
                $thisfile_audio['lossless']        = true;
                $thisfile_audio['channels']        = 1; // might be overriden below
                $thisfile_audio['bits_per_sample'] = 8; // might be overriden below

                // byte #     Description
                // ------     ------------------------------------------
                // 00-12      'Creative Voice File'
                // 13         1A (eof to abort printing of file)
                // 14-15      Offset of first datablock in .voc file (std 1A 00 in Intel Notation)
                // 16-17      Version number (minor,major) (VOC-HDR puts 0A 01)
                // 18-19      2's Comp of Ver. # + 1234h (VOC-HDR puts 29 11)

                $thisfile_voc['header']['datablock_offset'] = getid3_lib::LittleEndian2Int(substr($VOCheader, 20, 2));
                $thisfile_voc['header']['minor_version']    = getid3_lib::LittleEndian2Int(substr($VOCheader, 22, 1));
                $thisfile_voc['header']['major_version']    = getid3_lib::LittleEndian2Int(substr($VOCheader, 23, 1));

                do {

                        $BlockOffset    = ftell($fd);
                        $BlockData      = fread($fd, 4);
                        $BlockType      = ord($BlockData{0});
                        $BlockSize      = getid3_lib::LittleEndian2Int(substr($BlockData, 1, 3));
                        $ThisBlock      = array();

                        @$thisfile_voc['blocktypes'][$BlockType]++;
                        switch ($BlockType) {
                                case 0:  // Terminator
                                        // do nothing, we'll break out of the loop down below
                                        break;

                                case 1:  // Sound data
                                        $BlockData .= fread($fd, 2);
                                        if ($ThisFileInfo['avdataoffset'] <= $OriginalAVdataOffset) {
                                                $ThisFileInfo['avdataoffset'] = ftell($fd);
                                        }
                                        fseek($fd, $BlockSize - 2, SEEK_CUR);

                                        $ThisBlock['sample_rate_id']   = getid3_lib::LittleEndian2Int(substr($BlockData, 4, 1));
                                        $ThisBlock['compression_type'] = getid3_lib::LittleEndian2Int(substr($BlockData, 5, 1));

                                        $ThisBlock['compression_name'] = $this->VOCcompressionTypeLookup($ThisBlock['compression_type']);
                                        if ($ThisBlock['compression_type'] <= 3) {
                                                $thisfile_voc['compressed_bits_per_sample'] = getid3_lib::CastAsInt(str_replace('-bit', '', $ThisBlock['compression_name']));
                                        }

                                        // Less accurate sample_rate calculation than the Extended block (#8) data (but better than nothing if Extended Block is not available)
                                        if (empty($thisfile_audio['sample_rate'])) {
                                                // SR byte = 256 - (1000000 / sample_rate)
                                                $thisfile_audio['sample_rate'] = getid3_lib::trunc((1000000 / (256 - $ThisBlock['sample_rate_id'])) / $thisfile_audio['channels']);
                                        }
                                        break;

                                case 2:  // Sound continue
                                case 3:  // Silence
                                case 4:  // Marker
                                case 6:  // Repeat
                                case 7:  // End repeat
                                        // nothing useful, just skip
                                        fseek($fd, $BlockSize, SEEK_CUR);
                                        break;

                                case 8:  // Extended
                                        $BlockData .= fread($fd, 4);

                                        //00-01  Time Constant:
                                        //   Mono: 65536 - (256000000 / sample_rate)
                                        // Stereo: 65536 - (256000000 / (sample_rate * 2))
                                        $ThisBlock['time_constant'] =        getid3_lib::LittleEndian2Int(substr($BlockData, 4, 2));
                                        $ThisBlock['pack_method']   =        getid3_lib::LittleEndian2Int(substr($BlockData, 6, 1));
                                        $ThisBlock['stereo']        = (bool) getid3_lib::LittleEndian2Int(substr($BlockData, 7, 1));

                                        $thisfile_audio['channels']    = ($ThisBlock['stereo'] ? 2 : 1);
                                        $thisfile_audio['sample_rate'] = getid3_lib::trunc((256000000 / (65536 - $ThisBlock['time_constant'])) / $thisfile_audio['channels']);
                                        break;

                                case 9:  // data block that supersedes blocks 1 and 8. Used for stereo, 16 bit
                                        $BlockData .= fread($fd, 12);
                                        if ($ThisFileInfo['avdataoffset'] <= $OriginalAVdataOffset) {
                                                $ThisFileInfo['avdataoffset'] = ftell($fd);
                                        }
                                        fseek($fd, $BlockSize - 12, SEEK_CUR);

                                        $ThisBlock['sample_rate']      = getid3_lib::LittleEndian2Int(substr($BlockData,  4, 4));
                                        $ThisBlock['bits_per_sample']  = getid3_lib::LittleEndian2Int(substr($BlockData,  8, 1));
                                        $ThisBlock['channels']         = getid3_lib::LittleEndian2Int(substr($BlockData,  9, 1));
                                        $ThisBlock['wFormat']          = getid3_lib::LittleEndian2Int(substr($BlockData, 10, 2));

                                        $ThisBlock['compression_name'] = $this->VOCwFormatLookup($ThisBlock['wFormat']);
                                        if ($this->VOCwFormatActualBitsPerSampleLookup($ThisBlock['wFormat'])) {
                                                $thisfile_voc['compressed_bits_per_sample'] = $this->VOCwFormatActualBitsPerSampleLookup($ThisBlock['wFormat']);
                                        }

                                        $thisfile_audio['sample_rate']     = $ThisBlock['sample_rate'];
                                        $thisfile_audio['bits_per_sample'] = $ThisBlock['bits_per_sample'];
                                        $thisfile_audio['channels']        = $ThisBlock['channels'];
                                        break;

                                default:
                                        $ThisFileInfo['warning'][] = 'Unhandled block type "'.$BlockType.'" at offset '.$BlockOffset;
                                        fseek($fd, $BlockSize, SEEK_CUR);
                                        break;
                        }

                        if (!empty($ThisBlock)) {
                                $ThisBlock['block_offset']  = $BlockOffset;
                                $ThisBlock['block_size']    = $BlockSize;
                                $ThisBlock['block_type_id'] = $BlockType;
                                $thisfile_voc['blocks'][] = $ThisBlock;
                        }

                } while (!feof($fd) && ($BlockType != 0));

                // Terminator block doesn't have size field, so seek back 3 spaces
                fseek($fd, -3, SEEK_CUR);

                ksort($thisfile_voc['blocktypes']);

                if (!empty($thisfile_voc['compressed_bits_per_sample'])) {
                        $ThisFileInfo['playtime_seconds'] = (($ThisFileInfo['avdataend'] - $ThisFileInfo['avdataoffset']) * 8) / ($thisfile_voc['compressed_bits_per_sample'] * $thisfile_audio['channels'] * $thisfile_audio['sample_rate']);
                        $thisfile_audio['bitrate'] = (($ThisFileInfo['avdataend'] - $ThisFileInfo['avdataoffset']) * 8) / $ThisFileInfo['playtime_seconds'];
                }

                return true;
        }

        function VOCcompressionTypeLookup($index) {
                static $VOCcompressionTypeLookup = array(
                        0 => '8-bit',
                        1 => '4-bit',
                        2 => '2.6-bit',
                        3 => '2-bit'
                );
                return (isset($VOCcompressionTypeLookup[$index]) ? $VOCcompressionTypeLookup[$index] : 'Multi DAC ('.($index - 3).') channels');
        }

        function VOCwFormatLookup($index) {
                static $VOCwFormatLookup = array(
                        0x0000 => '8-bit unsigned PCM',
                        0x0001 => 'Creative 8-bit to 4-bit ADPCM',
                        0x0002 => 'Creative 8-bit to 3-bit ADPCM',
                        0x0003 => 'Creative 8-bit to 2-bit ADPCM',
                        0x0004 => '16-bit signed PCM',
                        0x0006 => 'CCITT a-Law',
                        0x0007 => 'CCITT u-Law',
                        0x2000 => 'Creative 16-bit to 4-bit ADPCM'
                );
                return (isset($VOCwFormatLookup[$index]) ? $VOCwFormatLookup[$index] : false);
        }

        function VOCwFormatActualBitsPerSampleLookup($index) {
                static $VOCwFormatLookup = array(
                        0x0000 => 8,
                        0x0001 => 4,
                        0x0002 => 3,
                        0x0003 => 2,
                        0x0004 => 16,
                        0x0006 => 8,
                        0x0007 => 8,
                        0x2000 => 4
                );
                return (isset($VOCwFormatLookup[$index]) ? $VOCwFormatLookup[$index] : false);
        }

}


?>