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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 | /** * ADTS parser helper */ import { logger } from '../utils/logger'; import { ErrorTypes, ErrorDetails } from '../errors'; export function getAudioConfig (observer, data, offset, audioCodec) { let adtsObjectType, // :int adtsSampleingIndex, // :int adtsExtensionSampleingIndex, // :int adtsChanelConfig, // :int config, userAgent = navigator.userAgent.toLowerCase(), manifestCodec = audioCodec, adtsSampleingRates = [ 96000, 88200, 64000, 48000, 44100, 32000, 24000, 22050, 16000, 12000, 11025, 8000, 7350]; // byte 2 adtsObjectType = ((data[offset + 2] & 0xC0) >>> 6) + 1; adtsSampleingIndex = ((data[offset + 2] & 0x3C) >>> 2); if (adtsSampleingIndex > adtsSampleingRates.length - 1) { observer.trigger(Event.ERROR, { type: ErrorTypes.MEDIA_ERROR, details: ErrorDetails.FRAG_PARSING_ERROR, fatal: true, reason: `invalid ADTS sampling index:${adtsSampleingIndex}` }); return; } adtsChanelConfig = ((data[offset + 2] & 0x01) << 2); // byte 3 adtsChanelConfig |= ((data[offset + 3] & 0xC0) >>> 6); logger.log(`manifest codec:${audioCodec},ADTS data:type:${adtsObjectType},sampleingIndex:${adtsSampleingIndex}[${adtsSampleingRates[adtsSampleingIndex]}Hz],channelConfig:${adtsChanelConfig}`); // firefox: freq less than 24kHz = AAC SBR (HE-AAC) if (/firefox/i.test(userAgent)) { if (adtsSampleingIndex >= 6) { adtsObjectType = 5; config = new Array(4); // HE-AAC uses SBR (Spectral Band Replication) , high frequencies are constructed from low frequencies // there is a factor 2 between frame sample rate and output sample rate // multiply frequency by 2 (see table below, equivalent to substract 3) adtsExtensionSampleingIndex = adtsSampleingIndex - 3; } else { adtsObjectType = 2; config = new Array(2); adtsExtensionSampleingIndex = adtsSampleingIndex; } // Android : always use AAC } else if (userAgent.indexOf('android') !== -1) { adtsObjectType = 2; config = new Array(2); adtsExtensionSampleingIndex = adtsSampleingIndex; } else { /* for other browsers (Chrome/Vivaldi/Opera ...) always force audio type to be HE-AAC SBR, as some browsers do not support audio codec switch properly (like Chrome ...) */ adtsObjectType = 5; config = new Array(4); // if (manifest codec is HE-AAC or HE-AACv2) OR (manifest codec not specified AND frequency less than 24kHz) if ((audioCodec && ((audioCodec.indexOf('mp4a.40.29') !== -1) || (audioCodec.indexOf('mp4a.40.5') !== -1))) || (!audioCodec && adtsSampleingIndex >= 6)) { // HE-AAC uses SBR (Spectral Band Replication) , high frequencies are constructed from low frequencies // there is a factor 2 between frame sample rate and output sample rate // multiply frequency by 2 (see table below, equivalent to substract 3) adtsExtensionSampleingIndex = adtsSampleingIndex - 3; } else { // if (manifest codec is AAC) AND (frequency less than 24kHz AND nb channel is 1) OR (manifest codec not specified and mono audio) // Chrome fails to play back with low frequency AAC LC mono when initialized with HE-AAC. This is not a problem with stereo. if (audioCodec && audioCodec.indexOf('mp4a.40.2') !== -1 && ((adtsSampleingIndex >= 6 && adtsChanelConfig === 1) || /vivaldi/i.test(userAgent)) || (!audioCodec && adtsChanelConfig === 1)) { adtsObjectType = 2; config = new Array(2); } adtsExtensionSampleingIndex = adtsSampleingIndex; } } /* refer to http://wiki.multimedia.cx/index.php?title=MPEG-4_Audio#Audio_Specific_Config ISO 14496-3 (AAC).pdf - Table 1.13 — Syntax of AudioSpecificConfig() Audio Profile / Audio Object Type 0: Null 1: AAC Main 2: AAC LC (Low Complexity) 3: AAC SSR (Scalable Sample Rate) 4: AAC LTP (Long Term Prediction) 5: SBR (Spectral Band Replication) 6: AAC Scalable sampling freq 0: 96000 Hz 1: 88200 Hz 2: 64000 Hz 3: 48000 Hz 4: 44100 Hz 5: 32000 Hz 6: 24000 Hz 7: 22050 Hz 8: 16000 Hz 9: 12000 Hz 10: 11025 Hz 11: 8000 Hz 12: 7350 Hz 13: Reserved 14: Reserved 15: frequency is written explictly Channel Configurations These are the channel configurations: 0: Defined in AOT Specifc Config 1: 1 channel: front-center 2: 2 channels: front-left, front-right */ // audioObjectType = profile => profile, the MPEG-4 Audio Object Type minus 1 config[0] = adtsObjectType << 3; // samplingFrequencyIndex config[0] |= (adtsSampleingIndex & 0x0E) >> 1; config[1] |= (adtsSampleingIndex & 0x01) << 7; // channelConfiguration config[1] |= adtsChanelConfig << 3; if (adtsObjectType === 5) { // adtsExtensionSampleingIndex config[1] |= (adtsExtensionSampleingIndex & 0x0E) >> 1; config[2] = (adtsExtensionSampleingIndex & 0x01) << 7; // adtsObjectType (force to 2, chrome is checking that object type is less than 5 ??? // https://chromium.googlesource.com/chromium/src.git/+/master/media/formats/mp4/aac.cc config[2] |= 2 << 2; config[3] = 0; } return { config: config, samplerate: adtsSampleingRates[adtsSampleingIndex], channelCount: adtsChanelConfig, codec: ('mp4a.40.' + adtsObjectType), manifestCodec: manifestCodec }; } export function isHeaderPattern (data, offset) { return data[offset] === 0xff && (data[offset + 1] & 0xf6) === 0xf0; } export function getHeaderLength (data, offset) { return (data[offset + 1] & 0x01 ? 7 : 9); } export function getFullFrameLength (data, offset) { return ((data[offset + 3] & 0x03) << 11) | (data[offset + 4] << 3) | ((data[offset + 5] & 0xE0) >>> 5); } export function isHeader (data, offset) { // Look for ADTS header | 1111 1111 | 1111 X00X | where X can be either 0 or 1 // Layer bits (position 14 and 15) in header should be always 0 for ADTS // More info https://wiki.multimedia.cx/index.php?title=ADTS if (offset + 1 < data.length && isHeaderPattern(data, offset)) return true; return false; } export function probe (data, offset) { // same as isHeader but we also check that ADTS frame follows last ADTS frame // or end of data is reached if (offset + 1 < data.length && isHeaderPattern(data, offset)) { // ADTS header Length let headerLength = getHeaderLength(data, offset); // ADTS frame Length let frameLength = headerLength; if (offset + 5 < data.length) frameLength = getFullFrameLength(data, offset); let newOffset = offset + frameLength; if (newOffset === data.length || (newOffset + 1 < data.length && isHeaderPattern(data, newOffset))) return true; } return false; } export function initTrackConfig (track, observer, data, offset, audioCodec) { if (!track.samplerate) { let config = getAudioConfig(observer, data, offset, audioCodec); track.config = config.config; track.samplerate = config.samplerate; track.channelCount = config.channelCount; track.codec = config.codec; track.manifestCodec = config.manifestCodec; logger.log(`parsed codec:${track.codec},rate:${config.samplerate},nb channel:${config.channelCount}`); } } export function getFrameDuration (samplerate) { return 1024 * 90000 / samplerate; } export function parseFrameHeader (data, offset, pts, frameIndex, frameDuration) { let headerLength, frameLength, stamp; let length = data.length; // The protection skip bit tells us if we have 2 bytes of CRC data at the end of the ADTS header headerLength = getHeaderLength(data, offset); // retrieve frame size frameLength = getFullFrameLength(data, offset); frameLength -= headerLength; if ((frameLength > 0) && ((offset + headerLength + frameLength) <= length)) { stamp = pts + frameIndex * frameDuration; // logger.log(`AAC frame, offset/length/total/pts:${offset+headerLength}/${frameLength}/${data.byteLength}/${(stamp/90).toFixed(0)}`); return { headerLength, frameLength, stamp }; } return undefined; } export function appendFrame (track, data, offset, pts, frameIndex) { let frameDuration = getFrameDuration(track.samplerate); let header = parseFrameHeader(data, offset, pts, frameIndex, frameDuration); if (header) { let stamp = header.stamp; let headerLength = header.headerLength; let frameLength = header.frameLength; // logger.log(`AAC frame, offset/length/total/pts:${offset+headerLength}/${frameLength}/${data.byteLength}/${(stamp/90).toFixed(0)}`); let aacSample = { unit: data.subarray(offset + headerLength, offset + headerLength + frameLength), pts: stamp, dts: stamp }; track.samples.push(aacSample); track.len += frameLength; return { sample: aacSample, length: frameLength + headerLength }; } return undefined; } |