Android外接midi设备的录音

本人借鉴了两篇文章：
https://www.midifan.com/modulearticle-detailview-901.htm 理论篇
https://www.midifan.com/modulearticle-detailview-902.htm 时间篇
实现了MidiRecordTool Midi录制类，
使用的流程是：
1、构造MidiRecordTool
2、start()开始的时候调用一次
3、writeEvent(x,x,x,x)开始写midi事件—周而复始的调用
4、finish()结束的时候调用一次
5、saveMidiToFile()将录制的midi文件保存，或调用getMidiBuffer获取内存中的midi数据

代码如下：

import java.io.FileOutputStream;
import java.io.IOException;
import java.util.LinkedList;
import java.util.List;/*** Created by mwt on 2017/8/29.* Single track*/public class MidiRecordTool {//private final String TAG = "MidiRecordSingleTrack";private MidiHead mMidiHead;private TrackHead mTrackHead;private EventStorageSpace mEventStorageSpace;private byte[] mBuffer;private long mSystemTime;private int mOneTickTime;//一个Tick的微妙数public final static byte[] mFinishBytes = {0x00, (byte) 0x91, 0x3C, 0x00, 0x00, (byte) 0xFF, 0x2F, 0x00};// name:曲谱名称 division:一个四分音符的tick数 speed:1分钟有多少个四分音符 numerator:分子 denominator:分母public MidiRecordTool(String name, int division, int speed, int numerator, int denominator) throws Exception {if (name == null)throw new Exception("String track name equle NULL");byte[] trackName = name.getBytes("UTF-8");mMidiHead = new MidiHead(division);mTrackHead = new TrackHead(trackName, speed, numerator, denominator);mOneTickTime = (int) ((1000000.0 * 60 / speed) / division);int headLen = mMidiHead.getMidiHeadLength() + mTrackHead.getTrackHeadLength();mEventStorageSpace = new EventStorageSpace(headLen);//Log.i(TAG, " mEventPosion:" + mEventPosion);mSystemTime = System.currentTimeMillis();}//开始录音调用一次public void start() {mSystemTime = System.currentTimeMillis();}//channel:通道 code:事件码 press:是否按下 speed:力度public synchronized void writeEvent(int channel, int code, boolean press, int speed) {long tmpTime = System.currentTimeMillis();long waste = tmpTime - mSystemTime;mSystemTime = tmpTime;long ticks = (waste * 1000 / mOneTickTime);byte[] time = trackTimeToBytes(ticks);int len = time.length + 3;//byte[] buffer = new byte[len];System.arraycopy(time, 0, buffer, 0, time.length);if (press)buffer[time.length] = (byte) (0x90 | (0xF & channel));elsebuffer[time.length] = (byte) (0x80 | (0xF & channel));buffer[time.length + 1] = (byte) (0xFF & code);buffer[time.length + 2] = (byte) (0xFF & speed);//mEventStorageSpace.writeEvent(buffer, len);writeEvent(buffer, len);}private void writeEvent(byte[] buffer, int len) {mEventStorageSpace.writeEvent(buffer, len);}//录音结束调用一次public void finish() {if (mBuffer == null) {writeEvent(mFinishBytes, mFinishBytes.length);mBuffer = mEventStorageSpace.getTotalBuffer();byte[] midiHead = mMidiHead.getMidiHeadBytes();byte[] trackHead = mTrackHead.getTrackHeadBytes(mEventStorageSpace.getEventLength());System.arraycopy(midiHead, 0, mBuffer, 0, midiHead.length);System.arraycopy(trackHead, 0, mBuffer, midiHead.length, trackHead.length);}}//保存录音曲谱public void saveMidiToFile(String fileName) throws IOException {//File file = new File(path);FileOutputStream fout = new FileOutputStream(fileName);if (mBuffer == null) {//结束mEventStorageSpace.writeEvent(mFinishBytes, mFinishBytes.length);mBuffer = mEventStorageSpace.getTotalBuffer();byte[] midiHead = mMidiHead.getMidiHeadBytes();byte[] trackHead = mTrackHead.getTrackHeadBytes(mEventStorageSpace.getEventLength());System.arraycopy(midiHead, 0, mBuffer, 0, midiHead.length);System.arraycopy(trackHead, 0, mBuffer, midiHead.length, trackHead.length);}fout.write(mBuffer);fout.close();}//获取录音内容public byte[] getMidiBuffer() {if (mBuffer == null) {//结束mEventStorageSpace.writeEvent(mFinishBytes, mFinishBytes.length);mBuffer = mEventStorageSpace.getTotalBuffer();byte[] midiHead = mMidiHead.getMidiHeadBytes();byte[] trackHead = mTrackHead.getTrackHeadBytes(mEventStorageSpace.getEventLength());System.arraycopy(midiHead, 0, mBuffer, 0, midiHead.length);System.arraycopy(trackHead, 0, mBuffer, midiHead.length, trackHead.length);}return mBuffer;}private byte[] trackTimeToBytes(long time) {byte[] tmp = new byte[8];int n = 0;if (time <= 0) {byte[] ret = {0x00};return ret;}while (time > 127) {tmp[n] = (byte) (time % 128);time = time / 128;n++;}if (time > 0) {tmp[n] = (byte) time;n++;}//除第一个字节，其它自己都加上0x80for (int i = 1; i < n; i++) {tmp[i] |= 0x80;}//高低位翻转byte[] result = new byte[n];for (int i = 0; i < n; i++) {result[i] = tmp[n - i - 1];}return result;}private byte[] swap2byte(int value) {byte[] result = new byte[2];result[0] = (byte) (value >> 8 & 0xFF);result[1] = (byte) (value & 0xFF);return result;}private byte[] swap3byte(int value) {byte[] result = new byte[3];result[0] = (byte) (value >> 16 & 0xFF);result[1] = (byte) (value >> 8 & 0xFF);result[2] = (byte) (value & 0xFF);return result;}private byte[] swap4byte(int value) {byte[] result = new byte[4];result[0] = (byte) (value >> 24 & 0xFF);result[1] = (byte) (value >> 16 & 0xFF);result[2] = (byte) (value >> 8 & 0xFF);result[3] = (byte) (value & 0xFF);return result;}/*** midi文件的头部类*/class MidiHead {//MIDI文件头byte[] MidiId = {0x4D, 0x54, 0x68, 0x64};//MIDI文件标志 MThdbyte[] midiInfoLen = {0x00, 0x00, 0x00, 0x06}; //头部信息长度 format + trackNUm + division的长度byte[] format = {0x00, 0x00}; //存放的格式 0x00 0x00:单音轨,0x00 0x01:多音轨且同步,0x00 02:多音轨但不同步byte[] trackNum = {0x00, 0x01}; //音轨数目byte[] division; //指定计数的方法，一种随时间计数（最高位设置为０时），另一种使用制式的时间码（最高位设置为１时）public MidiHead(int division) {this.division = swap2byte(division);}public int getMidiHeadLength() {return (MidiId.length + midiInfoLen.length + format.length + trackNum.length + division.length);}public byte[] getMidiHeadBytes() {int length = MidiId.length + midiInfoLen.length + format.length + trackNum.length + division.length;byte[] result = new byte[length];int posion = 0;System.arraycopy(MidiId, 0, result, posion, MidiId.length);posion += MidiId.length;System.arraycopy(midiInfoLen, 0, result, posion, midiInfoLen.length);posion += midiInfoLen.length;System.arraycopy(format, 0, result, posion, format.length);posion += format.length;System.arraycopy(trackNum, 0, result, posion, trackNum.length);posion += trackNum.length;System.arraycopy(division, 0, result, posion, division.length);return result;}}/*** 音轨的头部类*/class TrackHead {//音轨头byte[] mTrackId = {0x4D, 0x54, 0x72, 0x6B}; //磁道标志 MTrk// byte[] trackInfoByteNumber; //该轨道的字节数byte[] mTrackNameInfo;byte[] mTrackInfo = {0x00, (byte) 0xFF, 0x58, 0x04, 0x00, 0x00, 0x18, 0x08};//节拍信息byte[] mTrackController1 = {0x00, (byte) 0xB0, 0x0A, 0x40};//控制器信息byte[] mTrackController2 = {0x00, (byte) 0xB1, 0x0A, 0x40};//控制器信息byte[] mTrackSpeed = {0x00, (byte) 0xFF, 0x51, 0x03, 0x00, 0x00, 0x00};//节拍速度public TrackHead(byte[] name, int speed, int numerator, int denominator) {mTrackNameInfo = new byte[name.length + 4];mTrackNameInfo[0] = 0x00;mTrackNameInfo[1] = (byte) 0xFF;mTrackNameInfo[2] = 0x03;mTrackNameInfo[3] = (byte) (0xFF & name.length);System.arraycopy(name, 0, mTrackNameInfo, 4, name.length);mTrackInfo[4] = (byte) (0xFF & numerator);switch (denominator) {case 2:mTrackInfo[5] = 1;break;case 4:mTrackInfo[5] = 2;break;case 8:mTrackInfo[5] = 3;break;default:mTrackInfo[5] = 2;break;}int quarterTrackSpeed = (int) (1000000.0 * 60.0 / speed);byte[] quarterSpeedBytes = swap3byte(quarterTrackSpeed);System.arraycopy(quarterSpeedBytes, 0, mTrackSpeed, 4, 3);}public int getTrackHeadLength() {int totalLenght = 4 + 4+ mTrackNameInfo.length+ mTrackInfo.length+ mTrackController1.length+ mTrackController2.length+ mTrackSpeed.length;return totalLenght;}public byte[] getTrackHeadBytes(int eventLen) {int trackInfoLen = eventLen+ mTrackNameInfo.length+ mTrackInfo.length+ mTrackController1.length+ mTrackController2.length+ mTrackSpeed.length;byte[] trackInfoByteNumber = swap4byte(trackInfoLen);//该轨道的字节数int totalLenght = 4 + 4+ mTrackNameInfo.length+ mTrackInfo.length+ mTrackController1.length+ mTrackController2.length+ mTrackSpeed.length;byte[] result = new byte[totalLenght];int posion = 0;System.arraycopy(mTrackId, 0, result, posion, 4);posion += 4;System.arraycopy(trackInfoByteNumber, 0, result, posion, 4);posion += 4;System.arraycopy(mTrackNameInfo, 0, result, posion, mTrackNameInfo.length);posion += mTrackNameInfo.length;System.arraycopy(mTrackInfo, 0, result, posion, mTrackInfo.length);posion += mTrackInfo.length;System.arraycopy(mTrackController1, 0, result, posion, mTrackController1.length);posion += mTrackController1.length;System.arraycopy(mTrackController2, 0, result, posion, mTrackController2.length);posion += mTrackController2.length;System.arraycopy(mTrackSpeed, 0, result, posion, mTrackSpeed.length);return result;}}/*********************************** 动态存储空间类**********************************/class EventStorageSpace {private int mEventlength = 0;private int mHeadLength = 0;private byte[] mStorageBuffer;private List<StorageUnit> mStorageUnitList = new LinkedList<StorageUnit>();/*** headLen:头部空出的空间长度，为存放其它内容*/public EventStorageSpace(int headLen) {mHeadLength = headLen;}/*** 写入事件*/public void writeEvent(byte[] buffer, int len) {if (buffer == null) return;mEventlength += len;if (buffer == null || len <= 0) return;//第一次写走这个单元if (mStorageUnitList.size() <= 0) {StorageUnit newUnit = new StorageUnit();newUnit.writeBuffer(buffer, len);mStorageUnitList.add(newUnit);} else {//取出列表中的最后一个单元StorageUnit oldUnit = mStorageUnitList.get(mStorageUnitList.size() - 1);//查看这个单元是否可以再写了if (oldUnit.isCanInsert(len)) {oldUnit.writeBuffer(buffer, len);mStorageUnitList.set(mStorageUnitList.size() - 1, oldUnit);} else {StorageUnit newUnit = new StorageUnit();newUnit.writeBuffer(buffer, len);mStorageUnitList.add(newUnit);}}}/*** 获取存储空间的内容句柄*/public byte[] getTotalBuffer() {if (mStorageBuffer != null) mStorageBuffer = null;if (mEventlength == 0) {writeEvent(mFinishBytes, mFinishBytes.length);}mStorageBuffer = new byte[mHeadLength + mEventlength];int index = mHeadLength;for (int i = 0; i < mStorageUnitList.size(); i++) {StorageUnit unit = mStorageUnitList.get(i);int unitLen = unit.getLength();byte[] unitBuffer = unit.getUnitBuffers();System.arraycopy(unitBuffer, 0, mStorageBuffer, index, unitLen);index += unitLen;}return mStorageBuffer;}/*** 获取存储空间的总长度*/public int getTotalLength() {return (mHeadLength + mEventlength);}/*** 获取写入事件的总长度*/public int getEventLength() {return mEventlength;}/*********************************************** 动态存申请的一个小单元，容量是 TOTAL_LENGTH 个字节**********************************************/class StorageUnit {final int TOTAL_LENGTH = 1024;int posion = 0;byte[] mBuffer = new byte[TOTAL_LENGTH];/*** 判断是否可以写入*/public boolean isCanInsert(int len) {return (TOTAL_LENGTH - posion >= len);}/*** 写内容*/public void writeBuffer(byte[] buffer, int len) {if (buffer == null) return;for (int i = 0; i < len; i++) {mBuffer[posion++] = buffer[i];}}/*** 获取本单元的实际长度*/public int getLength() {return posion;}/*** 获取本单元的空间句柄*/public byte[] getUnitBuffers() {return mBuffer;}}}}

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