从音频PCM 16位到8位 - 获得噪音

Question

我实现了以下算法将PCM 16位音频数据转换为8位:

if(encoding == AudioFormat.ENCODING_PCM_8BIT){
    int len = data.length;          
    data1 = new byte[len/2];
    int tempint;

    for (int k = 0, i=1; i < len; i+=2, k++) {
        tempint = ((int)data[i]) ^ 0x00000080; 
        data1[k] = (byte)tempint;
    }
    data=null;
}

哪里data is byte[].运行此代码后,输出contains a lot of noise并告诉我,我在这里做错了.What should I do besides dropping the lower byte?

[编辑]:修改代码:

if(encoding == AudioFormat.ENCODING_PCM_8BIT){

            int len = data.length;          
            data1 = new byte[len/2];
            for (int i = 0; i < len/2; i++) {                   
                    data1[i] = data[i*2+1];     
            }

  }

the input/output looks like:

 Original data(counter:0) = 4
    Original data(counter:1) = -1
    Original data(counter:2) = 75
    Original data(counter:3) = -1
    Original data(counter:4) = 16
    Original data(counter:5) = -1
    Original data(counter:6) = 44
    Original data(counter:7) = -1
    Original data(counter:8) = 7
    Original data(counter:9) = -1
    Original data(counter:10) = 22
    Original data(counter:11) = -1
    Original data(counter:12) = 22
    Original data(counter:13) = -1
    Original data(counter:14) = 12
    Original data(counter:15) = -1

Output data:(counter:0) = -1
Output data:(counter:1) = -1
Output data:(counter:2) = -1
Output data:(counter:3) = -1
Output data:(counter:4) = -1
Output data:(counter:5) = -1
Output data:(counter:6) = -1
Output data:(counter:7) = -1
Output data:(counter:8) = -1
Output data:(counter:9) = -1
Output data:(counter:10) = -1
Output data:(counter:11) = -1
Output data:(counter:12) = -1
Output data:(counter:13) = -1
Output data:(counter:14) = -1
Output data:(counter:15) = -1

如果我丢弃第一个或第二个字节并不重要,噪声仍然存在.在这里我删除了第一个字节(而不是第二个)

Answer 1

以下算法大大减少了噪音量,但无法完全摆脱它:

if(encoding == AudioFormat.ENCODING_PCM_8BIT){  
            ShortBuffer intBuf = ByteBuffer.wrap(data).order(ByteOrder.LITTLE_ENDIAN).asShortBuffer();
            short[] samples16Bit = new short[intBuf.remaining()];
            intBuf.get(samples16Bit);
            data1 = new byte[samples16Bit.length];
            for (int i = 0; i < samples16Bit.length; i++) {
                data1[i] = (byte)((samples16Bit[i] / 256)+128);
            }
        }