mambax7 /
xoopseditors
| Total Complexity | 53 |
| Total Lines | 470 |
| Duplicated Lines | 0 % |
| Changes | 1 | ||
| Bugs | 0 | Features | 0 |
Complex classes like getid3_ac3 often do a lot of different things. To break such a class down, we need to identify a cohesive component within that class. A common approach to find such a component is to look for fields/methods that share the same prefixes, or suffixes.
Once you have determined the fields that belong together, you can apply the Extract Class refactoring. If the component makes sense as a sub-class, Extract Subclass is also a candidate, and is often faster.
While breaking up the class, it is a good idea to analyze how other classes use getid3_ac3, and based on these observations, apply Extract Interface, too.
| 1 | <?php |
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| 26 | class getid3_ac3 extends getid3_handler |
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| 27 | { |
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| 28 | |||
| 29 | public function Analyze() { |
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| 30 | |||
| 31 | $getid3 = $this->getid3; |
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| 32 | |||
| 33 | // http://www.atsc.org/standards/a_52a.pdf |
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| 34 | |||
| 35 | $getid3->info['fileformat'] = 'ac3'; |
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| 36 | $getid3->info['audio']['dataformat'] = 'ac3'; |
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| 37 | $getid3->info['audio']['bitrate_mode'] = 'cbr'; |
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| 38 | $getid3->info['audio']['lossless'] = false; |
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| 39 | |||
| 40 | $getid3->info['ac3']['raw']['bsi'] = array (); |
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| 41 | $info_ac3 = &$getid3->info['ac3']; |
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| 42 | $info_ac3_raw = &$info_ac3['raw']; |
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| 43 | $info_ac3_raw_bsi = &$info_ac3_raw['bsi']; |
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| 44 | |||
| 45 | |||
| 46 | // An AC-3 serial coded audio bit stream is made up of a sequence of synchronization frames |
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| 47 | // Each synchronization frame contains 6 coded audio blocks (AB), each of which represent 256 |
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| 48 | // new audio samples per channel. A synchronization information (SI) header at the beginning |
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| 49 | // of each frame contains information needed to acquire and maintain synchronization. A |
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| 50 | // bit stream information (BSI) header follows SI, and contains parameters describing the coded |
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| 51 | // audio service. The coded audio blocks may be followed by an auxiliary data (Aux) field. At the |
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| 52 | // end of each frame is an error check field that includes a CRC word for error detection. An |
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| 53 | // additional CRC word is located in the SI header, the use of which, by a decoder, is optional. |
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| 54 | // |
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| 55 | // syncinfo() | bsi() | AB0 | AB1 | AB2 | AB3 | AB4 | AB5 | Aux | CRC |
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| 56 | |||
| 57 | $this->fseek($getid3->info['avdataoffset'], SEEK_SET); |
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| 58 | $ac3_header['syncinfo'] = $this->fread(5); |
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|
Comprehensibility
Best Practice
introduced
by
|
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| 59 | $info_ac3_raw['synchinfo']['synchword'] = substr($ac3_header['syncinfo'], 0, 2); |
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| 60 | |||
| 61 | if ($info_ac3_raw['synchinfo']['synchword'] != "\x0B\x77") { |
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| 62 | throw new getid3_exception('Expecting "\x0B\x77" at offset '.$getid3->info['avdataoffset'].', found \x'.strtoupper(dechex($ac3_header['syncinfo']{0})).'\x'.strtoupper(dechex($ac3_header['syncinfo']{1})).' instead'); |
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| 63 | } |
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| 64 | |||
| 65 | |||
| 66 | // syncinfo() { |
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| 67 | // syncword 16 |
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| 68 | // crc1 16 |
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| 69 | // fscod 2 |
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| 70 | // frmsizecod 6 |
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| 71 | // } /* end of syncinfo */ |
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| 72 | |||
| 73 | $info_ac3_raw['synchinfo']['crc1'] = getid3_lib::LittleEndian2Int(substr($ac3_header['syncinfo'], 2, 2)); |
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| 74 | $ac3_synchinfo_fscod_frmsizecod = getid3_lib::LittleEndian2Int(substr($ac3_header['syncinfo'], 4, 1)); |
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| 75 | $info_ac3_raw['synchinfo']['fscod'] = ($ac3_synchinfo_fscod_frmsizecod & 0xC0) >> 6; |
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| 76 | $info_ac3_raw['synchinfo']['frmsizecod'] = ($ac3_synchinfo_fscod_frmsizecod & 0x3F); |
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| 77 | |||
| 78 | $info_ac3['sample_rate'] = getid3_ac3::AC3sampleRateCodeLookup($info_ac3_raw['synchinfo']['fscod']); |
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| 79 | if ($info_ac3_raw['synchinfo']['fscod'] <= 3) { |
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| 80 | $getid3->info['audio']['sample_rate'] = $info_ac3['sample_rate']; |
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| 81 | } |
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| 82 | |||
| 83 | $info_ac3['frame_length'] = getid3_ac3::AC3frameSizeLookup($info_ac3_raw['synchinfo']['frmsizecod'], $info_ac3_raw['synchinfo']['fscod']); |
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| 84 | $info_ac3['bitrate'] = getid3_ac3::AC3bitrateLookup($info_ac3_raw['synchinfo']['frmsizecod']); |
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| 85 | $getid3->info['audio']['bitrate'] = $info_ac3['bitrate']; |
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| 86 | |||
| 87 | $ac3_header['bsi'] = getid3_lib::BigEndian2Bin($this->fread(15)); |
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| 88 | |||
| 89 | $info_ac3_raw_bsi['bsid'] = bindec(substr($ac3_header['bsi'], 0, 5)); |
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| 90 | if ($info_ac3_raw_bsi['bsid'] > 8) { |
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| 91 | // Decoders which can decode version 8 will thus be able to decode version numbers less than 8. |
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| 92 | // If this standard is extended by the addition of additional elements or features, a value of bsid greater than 8 will be used. |
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| 93 | // Decoders built to this version of the standard will not be able to decode versions with bsid greater than 8. |
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| 94 | throw new getid3_exception('Bit stream identification is version '.$info_ac3_raw_bsi['bsid'].', but getID3() only understands up to version 8'); |
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| 95 | } |
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| 96 | |||
| 97 | $info_ac3_raw_bsi['bsmod'] = bindec(substr($ac3_header['bsi'], 5, 3)); |
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| 98 | $info_ac3_raw_bsi['acmod'] = bindec(substr($ac3_header['bsi'], 8, 3)); |
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| 99 | |||
| 100 | $info_ac3['service_type'] = getid3_ac3::AC3serviceTypeLookup($info_ac3_raw_bsi['bsmod'], $info_ac3_raw_bsi['acmod']); |
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| 101 | $ac3_coding_mode = getid3_ac3::AC3audioCodingModeLookup($info_ac3_raw_bsi['acmod']); |
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| 102 | foreach($ac3_coding_mode as $key => $value) { |
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| 103 | $info_ac3[$key] = $value; |
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| 104 | } |
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| 105 | switch ($info_ac3_raw_bsi['acmod']) { |
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| 106 | case 0: |
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| 107 | case 1: |
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| 108 | $getid3->info['audio']['channelmode'] = 'mono'; |
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| 109 | break; |
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| 110 | case 3: |
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| 111 | case 4: |
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| 112 | $getid3->info['audio']['channelmode'] = 'stereo'; |
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| 113 | break; |
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| 114 | default: |
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| 115 | $getid3->info['audio']['channelmode'] = 'surround'; |
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| 116 | break; |
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| 117 | } |
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| 118 | $getid3->info['audio']['channels'] = $info_ac3['num_channels']; |
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| 119 | |||
| 120 | $offset = 11; |
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| 121 | |||
| 122 | if ($info_ac3_raw_bsi['acmod'] & 0x01) { |
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| 123 | // If the lsb of acmod is a 1, center channel is in use and cmixlev follows in the bit stream. |
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| 124 | $info_ac3_raw_bsi['cmixlev'] = bindec(substr($ac3_header['bsi'], $offset, 2)); |
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| 125 | $info_ac3['center_mix_level'] = getid3_ac3::AC3centerMixLevelLookup($info_ac3_raw_bsi['cmixlev']); |
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| 126 | $offset += 2; |
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| 127 | } |
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| 128 | |||
| 129 | if ($info_ac3_raw_bsi['acmod'] & 0x04) { |
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| 130 | // If the msb of acmod is a 1, surround channels are in use and surmixlev follows in the bit stream. |
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| 131 | $info_ac3_raw_bsi['surmixlev'] = bindec(substr($ac3_header['bsi'], $offset, 2)); |
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| 132 | $info_ac3['surround_mix_level'] = getid3_ac3::AC3surroundMixLevelLookup($info_ac3_raw_bsi['surmixlev']); |
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| 133 | $offset += 2; |
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| 134 | } |
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| 135 | |||
| 136 | if ($info_ac3_raw_bsi['acmod'] == 0x02) { |
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| 137 | // When operating in the two channel mode, this 2-bit code indicates whether or not the program has been encoded in Dolby Surround. |
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| 138 | $info_ac3_raw_bsi['dsurmod'] = bindec(substr($ac3_header['bsi'], $offset, 2)); |
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| 139 | $info_ac3['dolby_surround_mode'] = getid3_ac3::AC3dolbySurroundModeLookup($info_ac3_raw_bsi['dsurmod']); |
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| 140 | $offset += 2; |
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| 141 | } |
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| 142 | |||
| 143 | $info_ac3_raw_bsi['lfeon'] = $ac3_header['bsi']{$offset++} == '1'; |
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| 144 | $info_ac3['lfe_enabled'] = $info_ac3_raw_bsi['lfeon']; |
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| 145 | if ($info_ac3_raw_bsi['lfeon']) { |
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| 146 | $getid3->info['audio']['channels'] .= '.1'; |
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| 147 | } |
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| 148 | |||
| 149 | $info_ac3['channels_enabled'] = getid3_ac3::AC3channelsEnabledLookup($info_ac3_raw_bsi['acmod'], $info_ac3_raw_bsi['lfeon']); |
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| 150 | |||
| 151 | // This indicates how far the average dialogue level is below digital 100 percent. Valid values are 1�31. |
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| 152 | // The value of 0 is reserved. The values of 1 to 31 are interpreted as -1 dB to -31 dB with respect to digital 100 percent. |
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| 153 | $info_ac3_raw_bsi['dialnorm'] = bindec(substr($ac3_header['bsi'], $offset, 5)); |
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| 154 | $offset += 5; |
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| 155 | $info_ac3['dialogue_normalization'] = '-'.$info_ac3_raw_bsi['dialnorm'].'dB'; |
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| 156 | |||
| 157 | $info_ac3_raw_bsi['compre_flag'] = $ac3_header['bsi']{$offset++} == '1'; |
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| 158 | if ($info_ac3_raw_bsi['compre_flag']) { |
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| 159 | $info_ac3_raw_bsi['compr'] = bindec(substr($ac3_header['bsi'], $offset, 8)); |
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| 160 | $offset += 8; |
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| 161 | |||
| 162 | $info_ac3['heavy_compression'] = getid3_ac3::AC3heavyCompression($info_ac3_raw_bsi['compr']); |
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| 163 | } |
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| 164 | |||
| 165 | $info_ac3_raw_bsi['langcode_flag'] = $ac3_header['bsi']{$offset++} == '1'; |
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| 166 | if ($info_ac3_raw_bsi['langcode_flag']) { |
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| 167 | $info_ac3_raw_bsi['langcod'] = bindec(substr($ac3_header['bsi'], $offset, 8)); |
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| 168 | $offset += 8; |
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| 169 | } |
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| 170 | |||
| 171 | $info_ac3_raw_bsi['audprodie'] = $ac3_header['bsi']{$offset++} == '1'; |
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| 172 | if ($info_ac3_raw_bsi['audprodie']) { |
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| 173 | $info_ac3_raw_bsi['mixlevel'] = bindec(substr($ac3_header['bsi'], $offset, 5)); |
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| 174 | $offset += 5; |
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| 175 | |||
| 176 | $info_ac3_raw_bsi['roomtyp'] = bindec(substr($ac3_header['bsi'], $offset, 2)); |
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| 177 | $offset += 2; |
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| 178 | |||
| 179 | $info_ac3['mixing_level'] = (80 + $info_ac3_raw_bsi['mixlevel']).'dB'; |
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| 180 | $info_ac3['room_type'] = getid3_ac3::AC3roomTypeLookup($info_ac3_raw_bsi['roomtyp']); |
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| 181 | } |
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| 182 | |||
| 183 | if ($info_ac3_raw_bsi['acmod'] == 0x00) { |
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| 184 | // If acmod is 0, then two completely independent program channels (dual mono) |
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| 185 | // are encoded into the bit stream, and are referenced as Ch1, Ch2. In this case, |
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| 186 | // a number of additional items are present in BSI or audblk to fully describe Ch2. |
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| 187 | |||
| 188 | |||
| 189 | // This indicates how far the average dialogue level is below digital 100 percent. Valid values are 1�31. |
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| 190 | // The value of 0 is reserved. The values of 1 to 31 are interpreted as -1 dB to -31 dB with respect to digital 100 percent. |
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| 191 | $info_ac3_raw_bsi['dialnorm2'] = bindec(substr($ac3_header['bsi'], $offset, 5)); |
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| 192 | $offset += 5; |
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| 193 | |||
| 194 | $info_ac3['dialogue_normalization2'] = '-'.$info_ac3_raw_bsi['dialnorm2'].'dB'; |
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| 195 | |||
| 196 | $info_ac3_raw_bsi['compre_flag2'] = $ac3_header['bsi']{$offset++} == '1'; |
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| 197 | if ($info_ac3_raw_bsi['compre_flag2']) { |
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| 198 | $info_ac3_raw_bsi['compr2'] = bindec(substr($ac3_header['bsi'], $offset, 8)); |
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| 199 | $offset += 8; |
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| 200 | |||
| 201 | $info_ac3['heavy_compression2'] = getid3_ac3::AC3heavyCompression($info_ac3_raw_bsi['compr2']); |
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| 202 | } |
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| 203 | |||
| 204 | $info_ac3_raw_bsi['langcode_flag2'] = $ac3_header['bsi']{$offset++} == '1'; |
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| 205 | if ($info_ac3_raw_bsi['langcode_flag2']) { |
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| 206 | $info_ac3_raw_bsi['langcod2'] = bindec(substr($ac3_header['bsi'], $offset, 8)); |
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| 207 | $offset += 8; |
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| 208 | } |
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| 209 | |||
| 210 | $info_ac3_raw_bsi['audprodie2'] = $ac3_header['bsi']{$offset++} == '1'; |
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| 211 | if ($info_ac3_raw_bsi['audprodie2']) { |
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| 212 | $info_ac3_raw_bsi['mixlevel2'] = bindec(substr($ac3_header['bsi'], $offset, 5)); |
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| 213 | $offset += 5; |
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| 214 | |||
| 215 | $info_ac3_raw_bsi['roomtyp2'] = bindec(substr($ac3_header['bsi'], $offset, 2)); |
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| 216 | $offset += 2; |
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| 217 | |||
| 218 | $info_ac3['mixing_level2'] = (80 + $info_ac3_raw_bsi['mixlevel2']).'dB'; |
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| 219 | $info_ac3['room_type2'] = getid3_ac3::AC3roomTypeLookup($info_ac3_raw_bsi['roomtyp2']); |
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| 220 | } |
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| 221 | |||
| 222 | } |
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| 223 | |||
| 224 | $info_ac3_raw_bsi['copyright'] = $ac3_header['bsi']{$offset++} == '1'; |
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| 225 | |||
| 226 | $info_ac3_raw_bsi['original'] = $ac3_header['bsi']{$offset++} == '1'; |
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| 227 | |||
| 228 | $info_ac3_raw_bsi['timecode1_flag'] = $ac3_header['bsi']{$offset++} == '1'; |
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| 229 | if ($info_ac3_raw_bsi['timecode1_flag']) { |
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| 230 | $info_ac3_raw_bsi['timecode1'] = bindec(substr($ac3_header['bsi'], $offset, 14)); |
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| 231 | $offset += 14; |
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| 232 | } |
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| 233 | |||
| 234 | $info_ac3_raw_bsi['timecode2_flag'] = $ac3_header['bsi']{$offset++} == '1'; |
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| 235 | if ($info_ac3_raw_bsi['timecode2_flag']) { |
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| 236 | $info_ac3_raw_bsi['timecode2'] = bindec(substr($ac3_header['bsi'], $offset, 14)); |
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| 237 | $offset += 14; |
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| 238 | } |
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| 239 | |||
| 240 | $info_ac3_raw_bsi['addbsi_flag'] = $ac3_header['bsi']{$offset++} == '1'; |
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| 241 | if ($info_ac3_raw_bsi['addbsi_flag']) { |
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| 242 | $info_ac3_raw_bsi['addbsi_length'] = bindec(substr($ac3_header['bsi'], $offset, 6)); |
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| 243 | $offset += 6; |
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| 244 | |||
| 245 | $ac3_header['bsi'] .= getid3_lib::BigEndian2Bin($this->fread($info_ac3_raw_bsi['addbsi_length'])); |
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| 246 | |||
| 247 | $info_ac3_raw_bsi['addbsi_data'] = substr($ac3_header['bsi'], 119, $info_ac3_raw_bsi['addbsi_length'] * 8); |
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| 248 | } |
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| 249 | |||
| 250 | return true; |
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| 251 | } |
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| 252 | |||
| 253 | |||
| 254 | |||
| 255 | public static function AC3sampleRateCodeLookup($fscod) { |
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| 256 | |||
| 257 | static $lookup = array ( |
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| 258 | 0 => 48000, |
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| 259 | 1 => 44100, |
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| 260 | 2 => 32000, |
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| 261 | 3 => 'reserved' // If the reserved code is indicated, the decoder should not attempt to decode audio and should mute. |
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| 262 | ); |
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| 263 | return (isset($lookup[$fscod]) ? $lookup[$fscod] : false); |
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| 264 | } |
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| 265 | |||
| 266 | |||
| 267 | |||
| 268 | public static function AC3serviceTypeLookup($bsmod, $acmod) { |
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| 269 | |||
| 270 | static $lookup = array ( |
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| 271 | 0 => 'main audio service: complete main (CM)', |
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| 272 | 1 => 'main audio service: music and effects (ME)', |
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| 273 | 2 => 'associated service: visually impaired (VI)', |
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| 274 | 3 => 'associated service: hearing impaired (HI)', |
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| 275 | 4 => 'associated service: dialogue (D)', |
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| 276 | 5 => 'associated service: commentary (C)', |
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| 277 | 6 => 'associated service: emergency (E)', |
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| 278 | 7 => 'main audio service: karaoke' |
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| 279 | ); |
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| 280 | |||
| 281 | if ($bsmod == 7 && $acmod == 1) { |
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| 282 | return 'associated service: voice over (VO)'; |
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| 283 | } |
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| 284 | |||
| 285 | return (isset($lookup[$bsmod]) ? $lookup[$bsmod] : false); |
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| 286 | } |
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| 287 | |||
| 288 | |||
| 289 | |||
| 290 | public static function AC3audioCodingModeLookup($acmod) { |
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| 291 | |||
| 292 | // array (channel configuration, # channels (not incl LFE), channel order) |
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| 293 | static $lookup = array ( |
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| 294 | 0 => array ('channel_config'=>'1+1', 'num_channels'=>2, 'channel_order'=>'Ch1,Ch2'), |
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| 295 | 1 => array ('channel_config'=>'1/0', 'num_channels'=>1, 'channel_order'=>'C'), |
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| 296 | 2 => array ('channel_config'=>'2/0', 'num_channels'=>2, 'channel_order'=>'L,R'), |
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| 297 | 3 => array ('channel_config'=>'3/0', 'num_channels'=>3, 'channel_order'=>'L,C,R'), |
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| 298 | 4 => array ('channel_config'=>'2/1', 'num_channels'=>3, 'channel_order'=>'L,R,S'), |
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| 299 | 5 => array ('channel_config'=>'3/1', 'num_channels'=>4, 'channel_order'=>'L,C,R,S'), |
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| 300 | 6 => array ('channel_config'=>'2/2', 'num_channels'=>4, 'channel_order'=>'L,R,SL,SR'), |
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| 301 | 7 => array ('channel_config'=>'3/2', 'num_channels'=>5, 'channel_order'=>'L,C,R,SL,SR') |
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| 302 | ); |
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| 303 | return (isset($lookup[$acmod]) ? $lookup[$acmod] : false); |
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| 304 | } |
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| 305 | |||
| 306 | |||
| 307 | |||
| 308 | public static function AC3centerMixLevelLookup($cmixlev) { |
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| 309 | |||
| 310 | static $lookup; |
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| 311 | if (!@$lookup) { |
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| 312 | $lookup = array ( |
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| 313 | 0 => pow(2, -3.0 / 6), // 0.707 (�3.0 dB) |
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| 314 | 1 => pow(2, -4.5 / 6), // 0.595 (�4.5 dB) |
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| 315 | 2 => pow(2, -6.0 / 6), // 0.500 (�6.0 dB) |
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| 316 | 3 => 'reserved' |
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| 317 | ); |
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| 318 | } |
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| 319 | return (isset($lookup[$cmixlev]) ? $lookup[$cmixlev] : false); |
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| 320 | } |
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| 321 | |||
| 322 | |||
| 323 | |||
| 324 | public static function AC3surroundMixLevelLookup($surmixlev) { |
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| 325 | |||
| 326 | static $lookup; |
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| 327 | if (!@$lookup) { |
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| 328 | $lookup = array ( |
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| 329 | 0 => pow(2, -3.0 / 6), |
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| 330 | 1 => pow(2, -6.0 / 6), |
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| 331 | 2 => 0, |
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| 332 | 3 => 'reserved' |
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| 333 | ); |
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| 334 | } |
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| 335 | return (isset($lookup[$surmixlev]) ? $lookup[$surmixlev] : false); |
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| 336 | } |
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| 337 | |||
| 338 | |||
| 339 | |||
| 340 | public static function AC3dolbySurroundModeLookup($dsurmod) { |
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| 341 | |||
| 342 | static $lookup = array ( |
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| 343 | 0 => 'not indicated', |
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| 344 | 1 => 'Not Dolby Surround encoded', |
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| 345 | 2 => 'Dolby Surround encoded', |
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| 346 | 3 => 'reserved' |
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| 347 | ); |
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| 348 | return (isset($lookup[$dsurmod]) ? $lookup[$dsurmod] : false); |
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| 349 | } |
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| 350 | |||
| 351 | |||
| 352 | |||
| 353 | public static function AC3channelsEnabledLookup($acmod, $lfeon) { |
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| 354 | |||
| 355 | return array ( |
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| 356 | 'ch1' => $acmod == 0, |
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| 357 | 'ch2' => $acmod == 0, |
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| 358 | 'left' => $acmod > 1, |
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| 359 | 'right' => $acmod > 1, |
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| 360 | 'center' => (bool)($acmod & 0x01), |
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| 361 | 'surround_mono' => $acmod == 4 || $acmod == 5, |
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| 362 | 'surround_left' => $acmod == 6 || $acmod == 7, |
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| 363 | 'surround_right' => $acmod == 6 || $acmod == 7, |
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| 364 | 'lfe' => $lfeon |
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| 365 | ); |
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| 366 | } |
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| 367 | |||
| 368 | |||
| 369 | |||
| 370 | public static function AC3heavyCompression($compre) { |
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| 371 | |||
| 372 | // The first four bits indicate gain changes in 6.02dB increments which can be |
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| 373 | // implemented with an arithmetic shift operation. The following four bits |
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| 374 | // indicate linear gain changes, and require a 5-bit multiply. |
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| 375 | // We will represent the two 4-bit fields of compr as follows: |
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| 376 | // X0 X1 X2 X3 . Y4 Y5 Y6 Y7 |
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| 377 | // The meaning of the X values is most simply described by considering X to represent a 4-bit |
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| 378 | // signed integer with values from �8 to +7. The gain indicated by X is then (X + 1) * 6.02 dB. The |
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| 379 | // following table shows this in detail. |
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| 380 | |||
| 381 | // Meaning of 4 msb of compr |
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| 382 | // 7 +48.16 dB |
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| 383 | // 6 +42.14 dB |
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| 384 | // 5 +36.12 dB |
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| 385 | // 4 +30.10 dB |
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| 386 | // 3 +24.08 dB |
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| 387 | // 2 +18.06 dB |
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| 388 | // 1 +12.04 dB |
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| 389 | // 0 +6.02 dB |
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| 390 | // -1 0 dB |
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| 391 | // -2 �6.02 dB |
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| 392 | // -3 �12.04 dB |
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| 393 | // -4 �18.06 dB |
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| 394 | // -5 �24.08 dB |
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| 395 | // -6 �30.10 dB |
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| 396 | // -7 �36.12 dB |
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| 397 | // -8 �42.14 dB |
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| 398 | |||
| 399 | $fourbit = str_pad(decbin(($compre & 0xF0) >> 4), 4, '0', STR_PAD_LEFT); |
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| 400 | if ($fourbit{0} == '1') { |
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| 401 | $log_gain = -8 + bindec(substr($fourbit, 1)); |
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| 402 | } else { |
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| 403 | $log_gain = bindec(substr($fourbit, 1)); |
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| 404 | } |
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| 405 | $log_gain = ($log_gain + 1) * (20 * log10(2)); |
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| 406 | |||
| 407 | // The value of Y is a linear representation of a gain change of up to �6 dB. Y is considered to |
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| 408 | // be an unsigned fractional integer, with a leading value of 1, or: 0.1 Y4 Y5 Y6 Y7 (base 2). Y can |
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| 409 | // represent values between 0.111112 (or 31/32) and 0.100002 (or 1/2). Thus, Y can represent gain |
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| 410 | // changes from �0.28 dB to �6.02 dB. |
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| 411 | |||
| 412 | $lin_gain = (16 + ($compre & 0x0F)) / 32; |
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| 413 | |||
| 414 | // The combination of X and Y values allows compr to indicate gain changes from |
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| 415 | // 48.16 � 0.28 = +47.89 dB, to |
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| 416 | // �42.14 � 6.02 = �48.16 dB. |
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| 417 | |||
| 418 | return $log_gain - $lin_gain; |
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| 419 | } |
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| 420 | |||
| 421 | |||
| 422 | |||
| 423 | public static function AC3roomTypeLookup($roomtyp) { |
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| 432 | } |
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| 433 | |||
| 434 | |||
| 435 | |||
| 436 | public static function AC3frameSizeLookup($frmsizecod, $fscod) { |
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| 467 | } |
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| 468 | |||
| 469 | |||
| 470 | |||
| 471 | public static function AC3bitrateLookup($frmsizecod) { |
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| 472 | |||
| 496 | } |
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| 497 | |||
| 498 | } |
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| 499 | |||
| 500 | ?> |
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