在 j2me 中是否可以测量 JSR-135 播放器制作的音频记录的信号幅度？
我知道我可以访问缓冲区，但是然后呢？
目标型号 Bold 9000，支持格式 PCM 和 AMR。我应该使用哪种格式？
另请参阅
Blackberry Audio Recording Sample Code
How To - Record Audio on a BlackBerry smartphone
谢谢！
【问题讨论】：
标签： blackberry audio java-me core-audio pcm
使用线程进行录音：
class VoiceNotesRecorderThread extends Thread {
private Player _player;
private RecordControl _rcontrol;
private ByteArrayOutputStream _output;
private byte _data[];
VoiceNotesRecorderThread() {
}
public void run() {
try {
_player = Manager
.createPlayer("capture://audio?encoding=audio/basic");
_player.realize();
_rcontrol = (RecordControl) _player
.getControl("RecordControl");
_output = new ByteArrayOutputStream();
_rcontrol.setRecordStream(_output);
_rcontrol.startRecord();
_player.start();
} catch (final Exception e) {
UiApplication.getUiApplication().invokeAndWait(new Runnable() {
public void run() {
Dialog.inform(e.toString());
}
});
}
}
public void stop() {
try {
_rcontrol.commit();
_data = _output.toByteArray();
_output.close();
_player.close();
} catch (Exception e) {
synchronized (UiApplication.getEventLock()) {
Dialog.inform(e.toString());
}
}
}
byte[] getData() {
return _data;
}
}
以及使用byte[]缓冲区绘制图形的方法：
private Bitmap getGraph(byte[] buffer, int zoom, int startFrom) {
Bitmap result = new Bitmap(Display.getWidth(), Display.getHeight());
Graphics g = new Graphics(result);
g.setColor(Color.BLACK);
int xPos = 0;
int yPos = Display.getHeight() >> 1;
for (int i = startFrom; i < buffer.length; i += 2 * zoom) {
byte[] b = new byte[] { buffer[i], buffer[i + 1] };
int level = (signedShortToInt(b) * 100 / 32767);
if (100 < level) {
level -= 200;
}
g.drawPoint(xPos, yPos - level);
xPos++;
}
return result;
}
public static final int signedShortToInt(byte[] b) {
int result = (b[0] & 0xff) | (b[1] & 0xff) << 8;
return result;
}
屏幕类：
class Scr extends MainScreen {
BitmapField mGraphField = new BitmapField(new Bitmap(Display.getWidth(),
Display.getHeight()));
private VoiceNotesRecorderThread m_thread;
public Scr() {
add(mGraphField);
add(new NullField(FOCUSABLE));
}
boolean mRecording = false;
private int mZoom = 1;
private int mStartFrom = 0;
byte[] mAudioData = null;
protected void makeMenu(Menu menu, int instance) {
super.makeMenu(menu, instance);
menu.add(mRecordStopMenuItem);
menu.add(mPaintZoomIn);
menu.add(mPaintZoomOut);
menu.add(mPaintZoomToFitScreen);
menu.add(mPaintMoveRight);
menu.add(mPaintMoveLeft);
menu.add(mPaintMoveToBegin);
}
MenuItem mRecordStopMenuItem = new MenuItem("Record", 0, 0) {
public void run() {
if (!mRecording) {
m_thread = new VoiceNotesRecorderThread();
m_thread.start();
mRecording = true;
this.setText("Stop");
} else {
m_thread.stop();
mAudioData = m_thread.getData();
zoomToFitScreen();
mRecording = false;
this.setText("Record");
}
}
};
MenuItem mPaintZoomIn = new MenuItem("Zoom In", 0, 0) {
public void run() {
zoomIn();
}
};
MenuItem mPaintZoomOut = new MenuItem("Zoom Out", 0, 0) {
public void run() {
zoomOut();
}
};
MenuItem mPaintZoomToFitScreen = new MenuItem("Fit Screen", 0, 0) {
public void run() {
zoomToFitScreen();
}
};
MenuItem mPaintMoveLeft = new MenuItem("Left", 0, 0) {
public void run() {
moveLeft();
}
};
MenuItem mPaintMoveRight = new MenuItem("Right", 0, 0) {
public void run() {
moveRight();
}
};
MenuItem mPaintMoveToBegin = new MenuItem("To Begin", 0, 0) {
public void run() {
moveToBegin();
}
};
private void zoomOut() {
if (mZoom < 200)
mZoom++;
mGraphField.setBitmap(getGraph(mAudioData, mZoom, mStartFrom));
}
private void zoomIn() {
if (mZoom > 1)
mZoom--;
mGraphField.setBitmap(getGraph(mAudioData, mZoom, mStartFrom));
}
private void zoomToFitScreen() {
int lenght = mAudioData.length;
mZoom = (lenght / 2) / Display.getWidth();
mGraphField.setBitmap(getGraph(mAudioData, mZoom, mStartFrom));
}
private void moveRight() {
if (mStartFrom < mAudioData.length - 30)
mStartFrom += 30;
mGraphField.setBitmap(getGraph(mAudioData, mZoom, mStartFrom));
}
private void moveLeft() {
if (mStartFrom > 30)
mStartFrom -= 30;
mGraphField.setBitmap(getGraph(mAudioData, mZoom, mStartFrom));
}
private void moveToBegin() {
mStartFrom = 0;
mGraphField.setBitmap(getGraph(mAudioData, mZoom, mStartFrom));
}
protected boolean navigationMovement(int dx, int dy, int status,
int time) {
if (dx < 0) {
moveLeft();
} else if (dx > 0) {
moveRight();
}
if (dy < 0) {
zoomIn();
} else if (dy > 0) {
zoomOut();
}
return super.navigationMovement(dx, dy, status, time);
}
}
很有帮助：
ADC -> integer PCM file -> signal processing
SO - How is audio represented with numbers?
Convert byte array to integer
【讨论】：
在大多数设备中，仅支持具有单个轨道的 MID 格式。那是在一个轨道中支持多种乐器的 mid0 格式。我不确定 api 是否提供了测量信号幅度的工具。要将 mid 文件转换为您可以使用具有免费和专业版本的Anvil Studio
要录制音频，您需要使用 Manager.createPlayer("capture://audio")。还要将编码（PCM 或 AMR）留给设备实现，因为某些手机不支持 PCM/AMR
希望这会有所帮助！
【讨论】：