J2ME/Blackberry - get audio signal amplitude level? - blackberry

Question

Is it possible in j2me to measure signal amplitude of audio record made by JSR-135 Player?
I know I can access buffer, but then what?
Target model Bold 9000, supported formats PCM and AMR. Which format I should use?
See also
Blackberry Audio Recording Sample Code
How To - Record Audio on a BlackBerry smartphone
Thank you!

Answer 1

Get raw PCM signal level
Use menu and trackwheel to zoom in/out and move left/right within graph.
Audio format: raw 8000 Hz 16 bit mono pcm.
Tested on Bold 9000 RIM OS 4.6
Algorythm should work in any mobile, where j2me and pcm is supported, of course implementation may require changes.
Using thread for audio recording:
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;
}
}
And method for painting graph using byte[] buffer:
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;
}
Screen class:
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);
}
}
Was helpfull:
ADC -> integer PCM file -> signal processing
SO - How is audio represented with numbers?
Convert byte array to integer

Answer 2

In most devices, only MID format with a single track is supported. That is the mid0 format that supports multiple instruments in one single track. I am not sure if the api provides the facility to measure the amplitude of a signal. To convert mid files to you can use Anvil Studio that has both free and pro versions
To record audio you need to use Manager.createPlayer("capture://audio"). Also leave the encoding (PCM or AMR) to the device implementation because some phones don't support PCM/AMR
Hope this helps!