compare_acoustid.js

compare_acoustid.js

const fs = require('fs')


let fp1Map = parseFPStr(fs.readFileSync('fpcalc.mp3.fp').toString('utf8'))
  , fp2Map = parseFPStr(fs.readFileSync('fpcalc-16.mp3.fp').toString('utf8'))
;

function parseFPStr(fpStr) {
    let lines = fpStr.split('\n')
      , map = Object.create(null)
    ;

    lines.forEach(function(line){
        let parts = line.split('=');
        map[parts.shift()] = parts.join('=');
    });

    map['FINGERPRINT'] = map['FINGERPRINT'].split(',').map(parseFloat);
    return map;
}

const ACOUSTID_MAX_ALIGN_OFFSET = 120
    , ACOUSTID_MAX_BIT_ERROR = 2
;

const POPCOUNT_TABLE_8BIT = [
    0,1,1,2,1,2,2,3,1,2,2,3,2,3,3,4,1,2,2,3,2,3,3,4,2,3,3,4,3,4,4,5,
    1,2,2,3,2,3,3,4,2,3,3,4,3,4,4,5,2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,
    1,2,2,3,2,3,3,4,2,3,3,4,3,4,4,5,2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,
    2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,3,4,4,5,4,5,5,6,4,5,5,6,5,6,6,7,
    1,2,2,3,2,3,3,4,2,3,3,4,3,4,4,5,2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,
    2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,3,4,4,5,4,5,5,6,4,5,5,6,5,6,6,7,
    2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,3,4,4,5,4,5,5,6,4,5,5,6,5,6,6,7,
    3,4,4,5,4,5,5,6,4,5,5,6,5,6,6,7,4,5,5,6,5,6,6,7,5,6,6,7,6,7,7,8
];

function popcount_lookup8(x) {
    return POPCOUNT_TABLE_8BIT[  x        & 0xff ] +
           POPCOUNT_TABLE_8BIT[ (x >>  8) & 0xff ] +
           POPCOUNT_TABLE_8BIT[ (x >> 16) & 0xff ] +
           POPCOUNT_TABLE_8BIT[  x >> 24         ];
}

function calculate_distance(fp1Arr, fp2Arr) {
    //must be one dimensional array
    //TODO: check

    //both Must have data
    //TODO: check return 0

    let totalLength = fp1Arr.length + fp2Arr.length + 1
      , counts = Array.apply(null, new Array(totalLength)).map(Number.prototype.valueOf, 0)
    ;

    console.log('FP1.length=%d FP2.length=%d', fp1Arr.length, fp2Arr.length);

    for(let i=0; i<fp1Arr.length; i++) {
        let jMin = Math.max(0, i-ACOUSTID_MAX_ALIGN_OFFSET)
          , jMax = Math.min(fp2Arr.length, i+ACOUSTID_MAX_ALIGN_OFFSET);
        ;
        for(let j=jMin; j<jMax; j++) {
            let bitErr = popcount_lookup8(fp1Arr[i] ^ fp2Arr[j]);
            //console.log('%s xor %s = %s', fp1Arr[i].toString(2), fp2Arr[j].toString(2), bitErr.toString(2));
            //console.log("comparing %d and %d with error %d", i, j, bitErr);
            if(bitErr <= ACOUSTID_MAX_BIT_ERROR) {
                let offset = i - j + fp2Arr.length;
                counts[offset] += 1;
            }
        }
    }

    //console.log(counts.join(','))

    let maxCount = Math.max.apply(Math, counts)
      , minLength = Math.min(fp1Arr.length, fp2Arr.length)
    return 1 - (maxCount / (1* minLength ));
}

console.log('Calculating distance from from "%s" to "%s"', fp1Map.FILE, fp2Map.FILE);
console.log('Distance=%s', calculate_distance(fp1Map.FINGERPRINT, fp2Map.FINGERPRINT));

hello hertzg
how much would you charge for implementing the same code with the aggrate framework in mongo db