Android(安卓)使用Visualizer获取播放音频的频率

最近项目中需要实时获取播放音频的频率，并绘制波形图，用到了Visualizer这个类，记录下其使用方法：

Visualizer.OnDataCaptureListener有两个回调方法，分别是onFftDataCapture和onWaveFormDataCapture，onFftDataCapture返回的是经过傅里叶变换处理后的音频数据，onWaveFormDataCapture返回的是声音的波形数据。

计算声音分贝部分代码：

val readyData = readyData(fft)val interval = readyData.size / (lineCount * 2)for (i in readyData.indices step interval) {...    val magnitude = readyData[i] * readyData[i] + readyData[i + 1] * readyData[i + 1] * 1.0    val dbValue = (10 * log10(magnitude)).toLong().coerceAtLeast(0) // 声音大小}private fun readyData(fft: ByteArray): ByteArray {    val newData = ByteArray(256) // 取一半    for (i in 0 until fft.size.coerceAtMost(256)) {        newData[i] = abs(fft[i].toInt()).toByte()    }    return newData}

Visualizer的使用：

class VisualizerHelper {    private var visualizer: Visualizer? = null    private var mediaPlayer: MediaPlayer? = null    /**     * 播放音乐     */    fun playMusic(        path: String,        onCompletionListener: MediaPlayer.OnCompletionListener,        onDataCaptureListener: Visualizer.OnDataCaptureListener    ) {        mediaPlayer = MediaPlayer().apply {            setDataSource(path)            setOnCompletionListener {                onCompletionListener.onCompletion(it)                release()                releaseVisualizer()                mediaPlayer = null            }        }        mediaPlayer?.prepare()        mediaPlayer?.start()        initVisualizer(onDataCaptureListener)    }    /**     * 停止播放     */    fun stopMusic() {        mediaPlayer?.run {            stop()            release()        }        mediaPlayer = null        releaseVisualizer()    }    /**     * 获取当前播放进度     */    fun getCurrentPosition(): Long {        return (mediaPlayer?.currentPosition ?: 0) / 1000L    }    private fun initVisualizer(        dataCaptureListener: Visualizer.OnDataCaptureListener    ) {        if (visualizer != null) {            visualizer?.enabled = true            return        }        visualizer = Visualizer(mediaPlayer?.audioSessionId ?: 0)        visualizer?.run {            captureSize = Visualizer.getCaptureSizeRange()[1] // 设置可视化数据的数据大小            setDataCaptureListener(                dataCaptureListener,                Visualizer.getMaxCaptureRate() / 2, // 采集频率                false,                true            )            enabled = true        }    }    /**     * 释放     */    private fun releaseVisualizer() {        visualizer?.run {            enabled = false            release()        }        visualizer = null    }}

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