rtp-parser.js

class EasyRtpParser {

    constructor() {
        
    }

    static parseRtpPacket(buf) {
        if(buf.length < EasyRtpParser.FIXED_HEADER_LENGTH) {
            throw new Error('can not parse buffer smaller than fixed header');
        }

        var firstByte = buf.readUInt8(0);
        var secondByte = buf.readUInt8(1);
        var version = firstByte >> 6;
        var padding = (firstByte >> 5) & 1;
        var extension = (firstByte >> 4) & 1;
        var csrcCount = firstByte & 0x0f;
        var marker = secondByte >> 7;
        var payloadType = secondByte & 0x7f;
        var sequenceNumber = buf.readUInt16BE(2);
        var timestamp = buf.readUInt32BE(4);
        var ssrc = buf.readUInt32BE(8);
    
        var offset = EasyRtpParser.FIXED_HEADER_LENGTH;
        var end = buf.length;
        if(end - offset >= 4 * csrcCount) {
            offset += 4 * csrcCount;
        } else {
            console.log(`no enough space for csrc`);
        }
        if(extension) {
            if(end - offset >= 4) {
                var extLen = 4 * (buf.readUInt16BE(offset + 2));
                offset += 4;
                if(end - offset >= extLen) {
                    offset += extLen;
                } else {
                    console.log(`no enough space for extension data`);
                }
            } else {
                console.log(`no enough space for extension header`);
            }
        }
        if(padding) {
            if(end - offset > 0) {
                var paddingBytes = buf.readUInt8(end - 1);
                if(end - offset >= paddingBytes) {
                    end -= paddingBytes;
                }
            }
        }
        var parsed = {
            version: version,
            padding: padding,
            extension: extension,
            csrcCount: csrcCount,
            marker: marker,
            payloadType: payloadType,
            sequenceNumber: sequenceNumber,
            timestamp: timestamp,
            ssrc: ssrc,
            payload: buf.slice(offset, end)
        };
        return parsed;
    }

    static parseRtpPayloadType(payloadType) {
        if (payloadType < 0 || payloadType > 127) {
            throw new Error('payload type range error');
        }
    
        return EasyRtpParser.payloadTypesHash[payloadType];
    }

    static isKeyframeStart(rtpRawdata) {
        // fu-a
        if(rtpRawdata.length >= 2 && rtpRawdata.readUInt8(0) == 0x7c && (rtpRawdata.readUInt8(1) == 0x87 || rtpRawdata.readUInt8(1) == 0x85)) { // fu-a
            return true;
        }
        return false;
    }
}

EasyRtpParser.payloadTypesHash = {
    0: {name: 'PCMU', mediaType: 'A', clockRate: 8000, channels: 1},
    1: {name: 'reserved', mediaType: 'A'},
    2: {name: 'reserved', mediaType: 'A'},
    3: {name: 'GSM' , mediaType: 'A', clockRate: 8000, channels: 1},
    4: {name: 'G723', mediaType: 'A', clockRate: 8000, channels: 1},
    5: {name: 'DVI4', mediaType: 'A', clockRate: 8000, channels: 1},
    6: {name: 'DVI4', mediaType: 'A', clockRate: 16000, channels: 1},
    7: {name: 'LPC', mediaType: 'A', clockRate: 8000, channels: 1},
    8: {name: 'PCMA', mediaType: 'A', clockRate: 8000, channels: 1},
    9: {name: 'G722', mediaType: 'A', clockRate: 8000, channels: 1},
    10: {name: 'L16', mediaType: 'A', clockRate: 44100, channels: 2},
    11: {name: 'L16', mediaType: 'A', clockRate: 44100, channels: 1},
    12: {name: 'QCELP', mediaType: 'A', clockRate: 8000, channels: 1},
    13: {name: 'CN', mediaType: 'A', clockRate: 8000, channels: 1},
    14: {name: 'MPA', mediaType: 'A', clockRate: 90000},
    15: {name: 'G728', mediaType: 'A', clockRate: 8000, channels: 1},
    16: {name: 'DVI4', mediaType: 'A', clockRate: 11025, channels: 1},
    17: {name: 'DVI4', mediaType: 'A', clockRate: 22050, channels: 1},
    18: {name: 'G729', mediaType: 'A', clockRate: 8000, channels: 1},
    19: {name: 'reserved', mediaType: 'A'},
    20: {name: 'unassigned', mediaType: 'A'},
    21: {name: 'unassigned', mediaType: 'A'},
    22: {name: 'unassigned', mediaType: 'A'},
    23: {name: 'unassigned', mediaType: 'A'},
    24: {name: 'unassigned', mediaType: 'V'},
    25: {name: 'CelB', mediaType: 'V', clockRate: 90000},
    26: {name: 'JPEG', mediaType: 'V', clockRate: 90000},
    27: {name: 'unassigned', mediaType: 'V'},
    28: {name: 'nv', mediaType: 'V', clockRate: 90000},
    29: {name: 'unassigned', mediaType: 'V'},
    30: {name: 'unassigned', mediaType: 'V'},
    31: {name: 'H261', mediaType: 'V', clockRate: 90000},
    32: {name: 'MPV', mediaType: 'V', clockRate: 90000},
    33: {name: 'MP2T', mediaType: 'AV', clockRate: 90000},
    34: {name: 'H263', mediaType: 'V', clockRate: 90000},
    35: {name: 'unassigned'},
    36: {name: 'unassigned'},
    37: {name: 'unassigned'},
    38: {name: 'unassigned'},
    39: {name: 'unassigned'},
    40: {name: 'unassigned'},
    41: {name: 'unassigned'},
    42: {name: 'unassigned'},
    43: {name: 'unassigned'},
    44: {name: 'unassigned'},
    45: {name: 'unassigned'},
    46: {name: 'unassigned'},
    47: {name: 'unassigned'},
    48: {name: 'unassigned'},
    49: {name: 'unassigned'},
    50: {name: 'unassigned'},
    51: {name: 'unassigned'},
    52: {name: 'unassigned'},
    53: {name: 'unassigned'},
    54: {name: 'unassigned'},
    55: {name: 'unassigned'},
    56: {name: 'unassigned'},
    57: {name: 'unassigned'},
    58: {name: 'unassigned'},
    59: {name: 'unassigned'},
    60: {name: 'unassigned'},
    61: {name: 'unassigned'},
    62: {name: 'unassigned'},
    63: {name: 'unassigned'},
    64: {name: 'unassigned'},
    65: {name: 'unassigned'},
    66: {name: 'unassigned'},
    67: {name: 'unassigned'},
    68: {name: 'unassigned'},
    69: {name: 'unassigned'},
    70: {name: 'unassigned'},
    71: {name: 'unassigned'},
    72: {name: 'reserved'},
    73: {name: 'reserved'},
    74: {name: 'reserved'},
    75: {name: 'reserved'},
    76: {name: 'reserved'},
    77: {name: 'unassigned'},
    78: {name: 'unassigned'},
    79: {name: 'unassigned'},
    80: {name: 'unassigned'},
    81: {name: 'unassigned'},
    82: {name: 'unassigned'},
    83: {name: 'unassigned'},
    84: {name: 'unassigned'},
    85: {name: 'unassigned'},
    86: {name: 'unassigned'},
    87: {name: 'unassigned'},
    88: {name: 'unassigned'},
    89: {name: 'unassigned'},
    90: {name: 'unassigned'},
    91: {name: 'unassigned'},
    92: {name: 'unassigned'},
    93: {name: 'unassigned'},
    94: {name: 'unassigned'},
    95: {name: 'unassigned'},
    96: {name: 'dynamic'},
    97: {name: 'dynamic'},
    98: {name: 'dynamic'},
    99: {name: 'dynamic'},
    100: {name: 'dynamic'},
    101: {name: 'dynamic'},
    102: {name: 'dynamic'},
    103: {name: 'dynamic'},
    104: {name: 'dynamic'},
    105: {name: 'dynamic'},
    106: {name: 'dynamic'},
    107: {name: 'dynamic'},
    108: {name: 'dynamic'},
    109: {name: 'dynamic'},
    110: {name: 'dynamic'},
    111: {name: 'dynamic'},
    112: {name: 'dynamic'},
    113: {name: 'dynamic'},
    114: {name: 'dynamic'},
    115: {name: 'dynamic'},
    116: {name: 'dynamic'},
    117: {name: 'dynamic'},
    118: {name: 'dynamic'},
    119: {name: 'dynamic'},
    120: {name: 'dynamic'},
    121: {name: 'dynamic'},
    122: {name: 'dynamic'},
    123: {name: 'dynamic'},
    124: {name: 'dynamic'},
    125: {name: 'dynamic'},
    126: {name: 'dynamic'},
    127: {name: 'dynamic'}
};

EasyRtpParser.FIXED_HEADER_LENGTH = 12;

module.exports = EasyRtpParser;