Question

我尝试使用以下方法将带有22050 randomNumbers的PCM文件从-1转换为1：

private void rawToWave(final File rawFile, final File waveFile) throws IOException {

    byte[] rawData = new byte[(int) rawFile.length()];
    DataInputStream input = null;
    try {
        input = new DataInputStream(new FileInputStream(rawFile));
        input.read(rawData);
    } finally {
        if (input != null) {
            input.close();
        }
    }

    DataOutputStream output = null;
    try {
        int myBitsPerSample= 16;
        int myFormat = 1;
        long myChannels = 1;
        long mySampleRate = 22050;
        long myByteRate = mySampleRate * myChannels * myBitsPerSample/8;
        int myBlockAlign = (int) (myChannels * myBitsPerSample/8);

        output = new DataOutputStream(new FileOutputStream(waveFile));
        // WAVE header
        // see http://ccrma.stanford.edu/courses/422/projects/WaveFormat/
        writeString(output, "RIFF"); // chunk id
        writeInt(output, 36 + rawData.length); // chunk size
        writeString(output, "WAVE"); // format
        writeString(output, "fmt "); // subchunk 1 id
        writeInt(output, 16); // subchunk 1 size
        writeShort(output, (short) 1); // audio format (1 = PCM)
        writeShort(output, (short) 1); // number of channels
        writeInt(output, (int)mySampleRate ); // sample ratemySampleRate
        writeInt(output, (int) (myByteRate)); // byte rate
        writeShort(output, (short) myBlockAlign); // block align
        writeShort(output, (short) 16); // bits per sample
        writeString(output, "data"); // subchunk 2 id
        writeInt(output, rawData.length); // subchunk 2 size
        // Audio data (conversion big endian -> little endian)
        short[] shorts = new short[rawData.length /2];
        ByteBuffer.wrap(rawData).order(ByteOrder.LITTLE_ENDIAN).asShortBuffer().get(shorts);
        ByteBuffer bytes = ByteBuffer.allocate(shorts.length * 2);



        for (short s : shorts) {
           bytes.putShort(s);
        }



        output.write(bytes.array());
    } finally {
        if (output != null) {
            output.close();
        }
    }
}

public  void writeShortLE(DataOutputStream out, short value) throws IOException {
    out.writeByte(value & 0xFF);
    out.writeByte((value >> 8) & 0xFF);
}



private void writeInt(final DataOutputStream output, final int value) throws IOException {
    output.write(value >> 0);
    output.write(value >> 8);
    output.write(value >> 16);
    output.write(value >> 24);
}

private void writeShort(final DataOutputStream output, final short value) throws IOException {
    output.write(value >> 0);
    output.write(value >> 8);
}

private void writeString(final DataOutputStream output, final String value) throws IOException {
    for (int i = 0; i < value.length(); i++) {
        output.write(value.charAt(i));
    }
}

我有一个双数组，从第一个元素到特定截止值的值为0，然后随机数直到第二个点，从此到文件的末尾再次为0。我在这个数组上做了一个反向fft并将值放入PCM文件中。 PCM-File应该输出一个whitenoise，但整个频谱上的噪声不仅高于截止频率。它适用于带有audiowrite的Matlab，但不适用于Java / Android。

从pcm文件中读取字节数组是否存在问题？我试图再次将两个wav文件导入到matlab中（在android中转换的一个和matlab中的一个）。来自matlab的那个具有与pcm文件相同的值和相同的值。在android中转换的那个具有超过229000个值和随机值，这些值与pcm文件中的不同。这两种转换方法之间的区别是什么？为什么它在matlab中正常工作而不是在android中使用这种方法？

将PCM-Data / PCM-File转换为Android / Java中的Wav-Audiofile

0 个答案: