如何在Android中轻松生成Synth和弦声音？

Question

如何在Android中轻松生成Synth和弦声音？我想能够使用8bit动态生成游戏音乐.尝试使用AudioTrack,但尚未获得好听的效果.

有什么例子吗？

我尝试了以下代码但没有成功:

public class BitLoose {
    private final int duration = 1; // seconds
    private final int sampleRate = 4200;
    private final int numSamples = duration * sampleRate;
    private final double sample[] = new double[numSamples];

    final AudioTrack audioTrack;

    public BitLoose() {
        audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC,
                sampleRate, AudioFormat.CHANNEL_CONFIGURATION_MONO,
                AudioFormat.ENCODING_PCM_8BIT, numSamples,
                AudioTrack.MODE_STREAM);
        audioTrack.play();
    }

    public void addTone(final int freqOfTone) {
        // fill out the array
        for (int i = 0; i < numSamples; ++i) {
            sample[i] = Math.sin(2 * Math.PI * i / (sampleRate / freqOfTone));
        }

        // convert to 16 bit pcm sound array
        // assumes the sample buffer is normalised.
        final byte generatedSnd[] = new byte[numSamples];

        int idx = 0;
        for (final double dVal : sample) {
            // scale to maximum amplitude
            final short val = (short) ((((dVal * 255))) % 255);
            // in 16 bit wav PCM, first byte is the low order byte
            generatedSnd[idx++] = (byte) (val);
        }
        audioTrack.write(generatedSnd, 0, sampleRate);
    }

    public void stop() {
        audioTrack.stop();
    }

Answer 1

我认为声音不好是由于音频格式造成的：AudioFormat.ENCODING_PCM_8BIT 使用无符号样本，因此 1 和 -1 之间的正弦必须转换为 0-255 字节值，试试这个：

for (final double dVal : sample) {
    final short val = (short) ((dVal + 1) / 2 * 255) ;
    generatedSnd[idx++] = (byte) val;
}

还可以尝试将采样率更改为 11025，因为某些设备可能不支持 4200：

private final int sampleRate = 11025;