Java如何将包含多个 double 的byte []转换为double []

Question

我有一个正在练习相位声码的声音文件。我已将文件的字节转换为 double[] 并通过快速傅立叶变换和快速傅立叶逆变换处理该文件的波形。现在的问题是我需要将 byte[] 转换回 double。以下是一些有用的代码片段:

我首先是如何转换数据的:

/**
 * Converts bytes from a TargetDataLine into a double[] allowing the information to be read.
 * NOTE: One byte is lost in the conversion so don't expect the arrays to be the same length!
 * @param bufferData The buffer read in from the target Data Line
 * @return the double[] that the buffer has been converted into.
 */
   private static double[] bytesToDoubleArray(byte[] bufferData){
    final int bytesRecorded = bufferData.length;
    final int bytesPerSample = getAudioFormat().getSampleSizeInBits()/8; 
    final double amplification = 100.0; // choose a number as you like
    double[] micBufferData = new double[bytesRecorded - bytesPerSample + 1];
    for (int index = 0, floatIndex = 0; index < bytesRecorded - bytesPerSample + 1; index += bytesPerSample, floatIndex++) {
        double sample = 0;
        for (int b = 0; b < bytesPerSample; b++) {
            int v = bufferData[index + b];
            if (b < bytesPerSample - 1 || bytesPerSample == 1) {
                v &= 0xFF;
            }
            sample += v << (b * 8);
        }
        double sample32 = amplification * (sample / 32768.0);
        micBufferData[floatIndex] = sample32;

    }
    return micBufferData;
}

以及我对数据所做的操作:

public static byte[] shift(byte[] data, int factor){
    double[] audioData = bytesToDoubleArray(data);
    audioData = Arrays.copyOf(audioData, roundToPowerOf2(audioData.length));
    Complex[] transformed = FFT.fft(doubleToComplex(audioData));
    transformed = shiftArray(transformed, 3);
    Complex[] reverted = FFT.ifft(transformed);
    for(int i = 0; i<reverted.length; i++){
        audioData[i] = reverted[i].re();
    }
    return null;//How do I convert audioData[] back into a byte[]????
}

关于如何解决这个问题有什么想法吗？任何解决方案将不胜感激。此外，任何已经实现相位声码的 Java 库也会很棒。

Answer 1

大概是这样。我确定我搞砸了。 scaleFactor 大概是 327.68，以反转上面的比例。上面的代码似乎是大端。是否需要 fullNormalize 取决于您。

public byte[] doubleArrayToByteArray(double[] input, int bytesPerSample, double scaleFactor, boolean fullNormalize, boolean bigEndian) {
    byte[] result = new byte[input.length * bytesPerSample];
    performNormalization(input, scaleFactor, fullNormalize);
    for (int i = 0; i < input.length; i++) {
        long sourceVal = (long)(input[i] * scaleFactor);
        sourceVal = sourceVal >> 8 * (8 - bytesPerSample);
        for (int j = 0; j < bytesPerSample; j++) {
            int index = i * bytesPerSample;
            if (bigEndian) {
                index += (bytesPerSample - j);
            }
            else {
                index += j;
            }
            result[index] = (byte) sourceVal;
            sourceVal = sourceVal >> 8;
        }
    }
    return result;
}

public void performNormalization(double[] input, double scaleFactor, boolean fullNormalize) {
    double maxVal = 0.0;
    for (int i = 0; i < input.length; i++) {
        double val = Math.abs(input[i]) * scaleFactor;
        if (val > maxVal) {
            maxVal = val;
        }
    }
    if (fullNormalize || maxVal > Long.MAX_VALUE) {
        double normalizeFactor = (double)(Long.MAX_VALUE) / maxVal;
        for (int i = 0; i < input.length; i++) {
            input[i] *= normalizeFactor;
        }
    }
}

更新:意识到我需要在规范化中考虑 scaleFactor。您通常不会同时指定不是 1.0 的 scaleFactor 和 fullNormalize = true。