waet-hammond-1

// Decode and perform WAVE file byte level manipulation

find_subarray = function(arr,subarr) {

    var arr_length = arr.length;

    var subarr_length = subarr.length;

    var last_check_index = arr_length - subarr_length;

    positionLoop:

    for (var i=0; i <= last_check_index; i++)

    {

        for (var j=0; j< subarr_length; j++)

        {

            if (arr[i + j] !== subarr[j]) {

                continue positionLoop;

            }

        }

        return i;

    }

    return -1;

};

function convertToInteger(arr) {

    var value = 0;

    for (var i=0; i<arr.length; i++)

    {

        value += arr[i]<<(i*8);

    }

    return value;

}

function convertToString(arr) {

    var str = "";

    for (var i=0; i<arr.length; i++)

    {

        str = str.concat(String.fromCharCode(arr[i]));

    }

    return str;

}

function WAVE()

{

    // The WAVE file object

    this.status == 'WAVE_DECLARED'

    this.decoded_data = null;

    this.RIFF = String(); //ChunkID

        this.size; //ChunkSize

        this.FT_Header; //Format

        this.fmt_marker; //Subchunk1ID

        this.formatDataLength; //Subchunk1Size

        this.type; //AudioFormat

        this.num_channels; //NumChannels

        this.sample_rate; //SampleRate

        this.byte_rate; //ByteRate

        this.block_align; //BlockAlign

        this.bits_per_sample; //BitsPerSample

        this.data_header; //Subchunk2ID

        this.data_size; //Subchunk2Size

    this.num_samples;

    this.open = function(IOArrayBuffer)

    {

        var IOView8 = new Uint8Array(IOArrayBuffer);

        this.RIFF = convertToString(IOView8.subarray(0,4));

        if (this.RIFF != 'RIFF')

        {

            console.log('WAVE ERR - Not a RIFF file');

            return 1;

        }

        this.size = convertToInteger(IOView8.subarray(4,8));

        this.FT_Header = convertToString(IOView8.subarray(8,12));

        this.fmt_marker = convertToString(IOView8.subarray(12,16));

        this.formatDataLength = convertToInteger(IOView8.subarray(16,20));

        this.type = convertToInteger(IOView8.subarray(20,22));

        this.num_channels = convertToInteger(IOView8.subarray(22,24));

        this.sample_rate = convertToInteger(IOView8.subarray(24,28));

        this.byte_rate = convertToInteger(IOView8.subarray(28,32));

        this.block_align = convertToInteger(IOView8.subarray(32,34));

        this.bits_per_sample = convertToInteger(IOView8.subarray(34,36));

        // Find the data header first

        var data_start = find_subarray(IOView8,[100, 97, 116, 97]);

        this.data_header = convertToString(IOView8.subarray(data_start,data_start+4));

        this.data_size = convertToInteger(IOView8.subarray(data_start+4,data_start+8));

        this.num_samples = this.data_size / this.block_align;

        this.decoded_data = [];

        if (this.type != 1 && this.type != 3) {

            console.log("Neither PCM nor IEEE float, cannot decode");

            return 1;

        }

        for (var c=0; c<this.num_channels; c++)

        {

            this.decoded_data.push(new Float32Array(this.num_samples));

        }

        var sampleDataOffset = data_start+8;

        // Now need to decode the data from sampleDataOffset

        // Data is always interleved

        var data_view;

        if (this.type == 3)

        {

            // Already in float

            if (this.bits_per_sample == 32) {

                data_view = new Float32Array(IOArrayBuffer.slice(sampleDataOffset,sampleDataOffset+this.data_size));

            } else if (this.bits_per_sample == 64) {

                data_view = new Float64Array(IOArrayBuffer.slice(sampleDataOffset,sampleDataOffset+this.data_size));

            }

        } else if (this.type == 1)

        {

            data_view = new Float32Array(this.num_samples*this.num_channels);

            integerConvert(new Uint8Array(IOArrayBuffer.slice(sampleDataOffset,sampleDataOffset+this.data_size)),data_view,this.bits_per_sample/8);

        }

        deInterlace(data_view,this.decoded_data);

        return 0;

    };

}

function deInterlace(src_array, dst_array)

{

    var number = src_array.length;

    var channels = dst_array.length;

    var channel_index = 0;

    var dst_index = 0;

    for (var n=0; n<number; n++)

    {

        dst_array[channel_index][dst_index] = src_array[n];

        channel_index++;

        if (channel_index >= channels) {

            channel_index = 0;

            dst_index++;

        }

    }

}

function integerConvert(srcView,dstView,srcBytes)

{

    //Convert integers of a Uint8Array of certain byte length into a Float32Array

    var number = dstView.length;

    var outBits = srcBytes*8;

    var endShift = 32 - outBits;

    if (srcView.length != dstView.length*srcBytes)

    {

        return -1;

    }

    for (var n=0; n<number; n++)

    {

        var srcIndex = n*srcBytes;

        var intData = convertToInteger(srcView.subarray(srcIndex,srcIndex+srcBytes));

        intData = (intData << (endShift));

        dstView[n] = intData / 2147483648;

    }

}