蓝牙avrcp协议源码分析
1,概述
1.1 avrcp协议
全称: Audio / Video Remote Control Profile音/视频远程控制协议
使用场景:不仅控制音频/视频,主要相当于一个远程遥控器,浏览手机上的文件,调整电视机上的菜单等等。
市场产品:蓝牙耳机,蓝牙遥控器,蓝牙自拍干等等
技术知识:
控制器: 远程控制设备,比如蓝牙自拍干
目标设备:比如手机,电视机
1.2 代码路径
客户端: frameworks\base\core\java\android\bluetooth
BluetoothAvrcp.java 定义的A/V 控制信号
BluetoothAvrcpController.java 协议的客户端
BluetoothAvrcpInfo.java 目标设备的元数据
服务端: packages\apps\Bluetooth\src\com\android\bluetooth\ avrcp
AvrcpControllerService.java 协议的服务端
BluetoothAvrcpDataProvider.java 元数据的数据库
Avrcp.java 还不知道这个类具体做什么的
2,接口
蓝牙遥控器的原理其实很简单,发送一个A/V控制信号就可以, BluetoothAvrcp文件提供了丰富的控制信号,简直就是一个遥控器。
public final class BluetoothAvrcp {
/*
* State flags for Passthrough commands
*/
public static final int PASSTHROUGH_STATE_PRESS = 0;
public static final int PASSTHROUGH_STATE_RELEASE = 1;
/*
* Operation IDs for Passthrough commands
*/
public static final int PASSTHROUGH_ID_SELECT = 0x00; /* select */
public static final int PASSTHROUGH_ID_UP = 0x01; /* up */
public static final int PASSTHROUGH_ID_DOWN = 0x02; /* down */
public static final int PASSTHROUGH_ID_LEFT = 0x03; /* left */
public static final int PASSTHROUGH_ID_RIGHT = 0x04; /* right */
public static final int PASSTHROUGH_ID_RIGHT_UP = 0x05; /* right-up */
public static final int PASSTHROUGH_ID_RIGHT_DOWN = 0x06; /* right-down */
public static final int PASSTHROUGH_ID_LEFT_UP = 0x07; /* left-up */
public static final int PASSTHROUGH_ID_LEFT_DOWN = 0x08; /* left-down */
public static final int PASSTHROUGH_ID_ROOT_MENU = 0x09; /* root menu */
public static final int PASSTHROUGH_ID_SETUP_MENU = 0x0A; /* setup menu */
public static final int PASSTHROUGH_ID_CONT_MENU = 0x0B; /* contents menu */
public static final int PASSTHROUGH_ID_FAV_MENU = 0x0C; /* favorite menu */
public static final int PASSTHROUGH_ID_EXIT = 0x0D; /* exit */
public static final int PASSTHROUGH_ID_0 = 0x20; /* 0 */
public static final int PASSTHROUGH_ID_1 = 0x21; /* 1 */
public static final int PASSTHROUGH_ID_2 = 0x22; /* 2 */
public static final int PASSTHROUGH_ID_3 = 0x23; /* 3 */
public static final int PASSTHROUGH_ID_4 = 0x24; /* 4 */
public static final int PASSTHROUGH_ID_5 = 0x25; /* 5 */
public static final int PASSTHROUGH_ID_6 = 0x26; /* 6 */
public static final int PASSTHROUGH_ID_7 = 0x27; /* 7 */
public static final int PASSTHROUGH_ID_8 = 0x28; /* 8 */
public static final int PASSTHROUGH_ID_9 = 0x29; /* 9 */
public static final int PASSTHROUGH_ID_DOT = 0x2A; /* dot */
public static final int PASSTHROUGH_ID_ENTER = 0x2B; /* enter */
public static final int PASSTHROUGH_ID_CLEAR = 0x2C; /* clear */
public static final int PASSTHROUGH_ID_CHAN_UP = 0x30; /* channel up */
public static final int PASSTHROUGH_ID_CHAN_DOWN = 0x31; /* channel down */
public static final int PASSTHROUGH_ID_PREV_CHAN = 0x32; /* previous channel */
public static final int PASSTHROUGH_ID_SOUND_SEL = 0x33; /* sound select */
public static final int PASSTHROUGH_ID_INPUT_SEL = 0x34; /* input select */
public static final int PASSTHROUGH_ID_DISP_INFO = 0x35; /* display information */
public static final int PASSTHROUGH_ID_HELP = 0x36; /* help */
public static final int PASSTHROUGH_ID_PAGE_UP = 0x37; /* page up */
public static final int PASSTHROUGH_ID_PAGE_DOWN = 0x38; /* page down */
public static final int PASSTHROUGH_ID_POWER = 0x40; /* power */
public static final int PASSTHROUGH_ID_VOL_UP = 0x41; /* volume up */
public static final int PASSTHROUGH_ID_VOL_DOWN = 0x42; /* volume down */
public static final int PASSTHROUGH_ID_MUTE = 0x43; /* mute */
public static final int PASSTHROUGH_ID_PLAY = 0x44; /* play */
public static final int PASSTHROUGH_ID_STOP = 0x45; /* stop */
public static final int PASSTHROUGH_ID_PAUSE = 0x46; /* pause */
public static final int PASSTHROUGH_ID_RECORD = 0x47; /* record */
public static final int PASSTHROUGH_ID_REWIND = 0x48; /* rewind */
public static final int PASSTHROUGH_ID_FAST_FOR = 0x49; /* fast forward */
public static final int PASSTHROUGH_ID_EJECT = 0x4A; /* eject */
public static final int PASSTHROUGH_ID_FORWARD = 0x4B; /* forward */
public static final int PASSTHROUGH_ID_BACKWARD = 0x4C; /* backward */
public static final int PASSTHROUGH_ID_ANGLE = 0x50; /* angle */
public static final int PASSTHROUGH_ID_SUBPICT = 0x51; /* subpicture */
public static final int PASSTHROUGH_ID_F1 = 0x71; /* F1 */
public static final int PASSTHROUGH_ID_F2 = 0x72; /* F2 */
public static final int PASSTHROUGH_ID_F3 = 0x73; /* F3 */
public static final int PASSTHROUGH_ID_F4 = 0x74; /* F4 */
public static final int PASSTHROUGH_ID_F5 = 0x75; /* F5 */
public static final int PASSTHROUGH_ID_VENDOR = 0x7E; /* vendor unique */
public static final int PASSTHROUGH_KEYPRESSED_RELEASE = 0x80;
}发送控制信号的BluetoothAvrcpController接口sendPassThroughCmd如下:
public void sendPassThroughCmd(BluetoothDevice device, int keyCode, int keyState) {
if (DBG) Log.d(TAG, "sendPassThroughCmd dev = " + device + " key " +
keyCode + " State = " + keyState);
if (mService != null && isEnabled()) {
try {
mService.sendPassThroughCmd(device, keyCode, keyState);
return;
} catch (RemoteException e) {
Log.e(TAG, "Error talking to BT service in sendPassThroughCmd()", e);
return;
}
}
if (mService == null) Log.w(TAG, "Proxy not attached to service");
}其中, BluetoothDevice是目标设备的蓝牙设备, keyCode是控制信号的键值, keyState 是键值的状态,0表示按下,1表示释放。
直接调用服务端(AvrcpControllerService)的sendPassThroughCmd方法,
比如,自己做开发时,发送暂停控制信号,
public static final int AVRC_ID_PAUSE = 0x46;
public static final int KEY_STATE_PRESSED = 0;
public static final int KEY_STATE_RELEASED = 1;
public boolean SendPassThruPause(BluetoothDevice mDevice) {
if ((mAvrcpController != null) && (mDevice != null) &&
(BluetoothProfile.STATE_DISCONNECTED !=
(mAvrcpController.getConnectionState(mDevice)))){
mAvrcpController.sendPassThroughCmd(mDevice, AVRC_ID_PAUSE, KEY_STATE_PRESSED);
mAvrcpController.sendPassThroughCmd(mDevice, AVRC_ID_PAUSE, KEY_STATE_RELEASED);
return true;
} else {
return false;
}3,小结
avrcp协议虽然使用简单,但是能做很多事情,还有疑惑的地方:
1,BluetoothAvrcpInfo.java和Avrcp.java 不知道具体做什么的
2, BluetoothAvrcpController的getMetaData接口本意是获取元数据,但是又没有返回值
3,服务端AvrcpControllerService的方法比客户端的方法要多很多,也不知道有什么作用。