PCM与G711A互转

工具类（Java）
调用方法（Kotlin）

工具类（Java）

public class G711Code {private final static int SIGN_BIT = 0x80;private final static int QUANT_MASK = 0xf;private final static int SEG_SHIFT = 4;private final static int SEG_MASK = 0x70;static short[] seg_end = {0xFF, 0x1FF, 0x3FF, 0x7FF,0xFFF, 0x1FFF, 0x3FFF, 0x7FFF};static short search(short val,short[] table,short size){for (short i = 0 ; i < size; i++) {if(val <= table[i]){return i;}}return size;}static byte linear2alaw(short pcm_val){short mask;short seg;char aval;if(pcm_val >= 0){mask = 0xD5;}else{mask = 0x55;pcm_val = (short) (-pcm_val - 1);if(pcm_val < 0){pcm_val = 32767;}}/* Convert the scaled magnitude to segment number. */seg = search(pcm_val, seg_end, (short) 8);/* Combine the sign, segment, and quantization bits. */if (seg >= 8)       /* out of range, return maximum value. */return (byte) (0x7F ^ mask);else {aval = (char) (seg << SEG_SHIFT);if (seg < 2)aval |= (pcm_val >> 4) & QUANT_MASK;elseaval |= (pcm_val >> (seg + 3)) & QUANT_MASK;return (byte) (aval ^ mask);}}static short alaw2linear(byte a_val){short       t;short       seg;a_val ^= 0x55;t = (short) ((a_val & QUANT_MASK) << 4);seg = (short) ((a_val & SEG_MASK) >> SEG_SHIFT);switch (seg) {case 0:t += 8;break;case 1:t += 0x108;break;default:t += 0x108;t <<= seg - 1;}return (a_val & SIGN_BIT) != 0 ? t : (short) -t;}/*** pcm 转 g711a* @param pcm* @param code* @param size*/public static void G711aEncoder(short[] pcm,byte[] code,int size){for(int i=0;i<size;i++){code[i]=linear2alaw(pcm[i]);
//            Log.e("-------------","数据编码:"+code[i]);}}/*** g711a 转 pcm* @param pcm* @param code* @param size*/public static void G711aDecoder(short[] pcm,byte[] code,int size){for(int i=0;i<size;i++){pcm[i]=alaw2linear(code[i]);}}/*** byte转short* @param data* @return*/public static short[] byteToShort(byte[] data) {short[] shortValue = new short[data.length / 2];for (int i = 0; i < shortValue.length; i++) {shortValue[i] = (short) ((data[i * 2] & 0xff) | ((data[i * 2 + 1] & 0xff) << 8));}return shortValue;}/*** short转byte* @param data* @return*/public static byte[] shortToByte(short[] data) {byte[] byteValue = new byte[data.length * 2];for (int i = 0; i < data.length; i++) {byteValue[i * 2] = (byte) (data[i] & 0xff);byteValue[i * 2 + 1] = (byte) ((data[i] & 0xff00) >> 8);}return byteValue;}}

调用方法（Kotlin）

	/*** ffmpeg -f s16le -i customAudio1.pcm -f alaw customAudio1.pcm.g711a* ffplay -f s16le -ar 8000 customAudio1.pcm* ffplay -f alaw -ar 8000 customAudio1.pcm.g711a** 可以用进制软件比如hexviewer查看对比ffmpeg转化的g711a文件* 或者使用ffplay播放显示波形*/fun pcm2g711a(){val inputStream: InputStream = assets.open("customAudio1.pcm")val available = inputStream.available()Log.e("TAG","available:"+available)val bytes: ByteArray = ByteArray(available)val byteCount = inputStream.read(bytes)Log.e("TAG","byteCount:"+byteCount)//文件大可能需要循环读取
//        val bytes: ByteArray = ByteArray(1024)
//        var byteCount = inputStream.read(bytes)
//        Log.e("TAG","start byteCount:"+byteCount)
//        while (byteCount != -1){
//            byteCount = inputStream.read(bytes)
//            Log.e("TAG","byteCount:"+byteCount)
//        }
//        Log.e("TAG","end byteCount:"+byteCount)val shortPCM: ShortArray = G711Code.byteToShort(bytes)//一定要转！！！val bytesG711A: ByteArray = ByteArray(available)Log.e("TAG","shortPCM.size:"+shortPCM.size)G711Code.G711aEncoder(shortPCM,bytesG711A,shortPCM.size)Log.e("TAG","bytesG711A.size:"+bytesG711A.size)val file = File(getExternalFilesDir(null)?.absolutePath+"/customAudio1_"+System.currentTimeMillis()+".g711a")val fos = FileOutputStream(file)fos.write(bytesG711A)Log.e("TAG","write end")inputStream.close()fos.flush()fos.close()}fun g711a2pcm(){val inputStream: InputStream = assets.open("customAudio1.pcm.g711a")val available = inputStream.available()Log.e("TAG","available:"+available)val bytes: ByteArray = ByteArray(available)val byteCount = inputStream.read(bytes)Log.e("TAG","byteCount:"+byteCount)//文件大可能需要循环读取
//        val bytes: ByteArray = ByteArray(1024)
//        var byteCount = inputStream.read(bytes)
//        Log.e("TAG","start byteCount:"+byteCount)
//        while (byteCount != -1){
//            byteCount = inputStream.read(bytes)
//            Log.e("TAG","byteCount:"+byteCount)
//        }
//        Log.e("TAG","end byteCount:"+byteCount)//        val bytesPCMEmpty: ByteArray = ByteArray(available)
//        Log.e("TAG","bytesPCMEmpty.size:"+bytesPCMEmpty.size)
//        val shortPCM: ShortArray = G711Code.byteToShort(bytesPCMEmpty)//会丢失后面一段数据！！！val shortPCM: ShortArray = ShortArray(available)Log.e("TAG","shortPCM.size:"+shortPCM.size)G711Code.G711aDecoder(shortPCM,bytes,bytes.size)Log.e("TAG","shortPCM.size:"+shortPCM.size)val file = File(getExternalFilesDir(null)?.absolutePath+"/customAudio1_"+System.currentTimeMillis()+".pcm")val fos = FileOutputStream(file)val bytesPCM: ByteArray = G711Code.shortToByte(shortPCM)fos.write(bytesPCM)Log.e("TAG","write end")inputStream.close()fos.flush()fos.close()}