Android Audio 音频路由
一、在 AudioPolicyService 中，选择音频路由时会从当前音频流的类型获取音频的路由策略：
/frameworks/av/services/audiopolicy/managerdefault/AudioPolicyManager.cpp
routing_strategy AudioPolicyManager::getStrategy(audio_stream_type_t stream) const
{
ALOG_ASSERT(stream != AUDIO_STREAM_PATCH,"getStrategy() called for AUDIO_STREAM_PATCH");
return mEngine->getStrategyForStream(stream);
}/frameworks/av/services/audiopolicy/enginedefault/src/Engine.cpp
routing_strategy Engine::getStrategyForStream(audio_stream_type_t stream)
{
// stream to strategy mapping
switch (stream) {
case AUDIO_STREAM_VOICE_CALL:
case AUDIO_STREAM_BLUETOOTH_SCO:
return STRATEGY_PHONE;
case AUDIO_STREAM_RING:
case AUDIO_STREAM_ALARM:
return STRATEGY_SONIFICATION;
case AUDIO_STREAM_NOTIFICATION:
return STRATEGY_SONIFICATION_RESPECTFUL;
case AUDIO_STREAM_DTMF:
return STRATEGY_DTMF;
default:
ALOGE("unknown stream type %d", stream);
case AUDIO_STREAM_SYSTEM:
// NOTE: SYSTEM stream uses MEDIA strategy because muting music and switching outputs
// while key clicks are played produces a poor result
case AUDIO_STREAM_MUSIC:
return STRATEGY_MEDIA;
case AUDIO_STREAM_ENFORCED_AUDIBLE:
return STRATEGY_ENFORCED_AUDIBLE;
case AUDIO_STREAM_TTS:
return STRATEGY_TRANSMITTED_THROUGH_SPEAKER;
case AUDIO_STREAM_ACCESSIBILITY:
return STRATEGY_ACCESSIBILITY;
case AUDIO_STREAM_REROUTING:
return STRATEGY_REROUTING;
}
}音频策略枚举：
enum routing_strategy {
STRATEGY_MEDIA, // 媒体策略
STRATEGY_PHONE, // 电话策略
STRATEGY_SONIFICATION, // 通知策略
STRATEGY_SONIFICATION_RESPECTFUL,
STRATEGY_DTMF, // DTMF 策略
STRATEGY_ENFORCED_AUDIBLE, // 强制输出策略
STRATEGY_TRANSMITTED_THROUGH_SPEAKER,
STRATEGY_ACCESSIBILITY,
STRATEGY_REROUTING,
NUM_STRATEGIES
};二、获取到音频路由策略类型后，通过调用 getDeviceForStrategy() 选择最终的输出设备
/frameworks/av/services/audiopolicy/enginedefault/src/Engine.cpp
audio_devices_t Engine::getDeviceForStrategy(routing_strategy strategy) const
{
DeviceVector availableOutputDevices = mApmObserver->getAvailableOutputDevices();
DeviceVector availableInputDevices = mApmObserver->getAvailableInputDevices();
const SwAudioOutputCollection &outputs = mApmObserver->getOutputs();
return getDeviceForStrategyInt(strategy, availableOutputDevices,
availableInputDevices, outputs, (uint32_t)AUDIO_DEVICE_NONE);
}audio_devices_t Engine::getDeviceForStrategyInt(routing_strategy strategy,
DeviceVector availableOutputDevices,
DeviceVector availableInputDevices,
const SwAudioOutputCollection &outputs,
uint32_t outputDeviceTypesToIgnore) const
{
uint32_t device = AUDIO_DEVICE_NONE;
uint32_t availableOutputDevicesType =
availableOutputDevices.types() & ~outputDeviceTypesToIgnore;
switch (strategy) {
... ...
case STRATEGY_MEDIA: {
uint32_t device2 = AUDIO_DEVICE_NONE;
if (strategy != STRATEGY_SONIFICATION) {
// no sonification on remote submix (e.g. WFD)
if (availableOutputDevices.getDevice(AUDIO_DEVICE_OUT_REMOTE_SUBMIX,
String8("0")) != 0) {
device2 = availableOutputDevices.types() & AUDIO_DEVICE_OUT_REMOTE_SUBMIX;
}
}
if (isInCall() && (strategy == STRATEGY_MEDIA)) {
device = getDeviceForStrategyInt(
STRATEGY_PHONE, availableOutputDevices, availableInputDevices, outputs,
outputDeviceTypesToIgnore);
break;
}
if (device2 == AUDIO_DEVICE_NONE) {
device2 = availableOutputDevicesType & AUDIO_DEVICE_OUT_HEARING_AID;
}
if ((device2 == AUDIO_DEVICE_NONE) &&
(mForceUse[AUDIO_POLICY_FORCE_FOR_MEDIA] != AUDIO_POLICY_FORCE_NO_BT_A2DP) &&
outputs.isA2dpSupported()) {
device2 = availableOutputDevicesType & AUDIO_DEVICE_OUT_BLUETOOTH_A2DP;
if (device2 == AUDIO_DEVICE_NONE) {
device2 = availableOutputDevicesType & AUDIO_DEVICE_OUT_BLUETOOTH_A2DP_HEADPHONES;
}
if (device2 == AUDIO_DEVICE_NONE) {
device2 = availableOutputDevicesType & AUDIO_DEVICE_OUT_BLUETOOTH_A2DP_SPEAKER;
}
}
if ((device2 == AUDIO_DEVICE_NONE) &&
(mForceUse[AUDIO_POLICY_FORCE_FOR_MEDIA] == AUDIO_POLICY_FORCE_SPEAKER)) {
device2 = availableOutputDevicesType & AUDIO_DEVICE_OUT_SPEAKER;
}
if (device2 == AUDIO_DEVICE_NONE) {
device2 = availableOutputDevicesType & AUDIO_DEVICE_OUT_WIRED_HEADPHONE;
}
if (device2 == AUDIO_DEVICE_NONE) {
device2 = availableOutputDevicesType & AUDIO_DEVICE_OUT_LINE;
}
if (device2 == AUDIO_DEVICE_NONE) {
device2 = availableOutputDevicesType & AUDIO_DEVICE_OUT_WIRED_HEADSET;
}
if (device2 == AUDIO_DEVICE_NONE) {
device2 = availableOutputDevicesType & AUDIO_DEVICE_OUT_USB_HEADSET;
}
if (device2 == AUDIO_DEVICE_NONE) {
device2 = availableOutputDevicesType & AUDIO_DEVICE_OUT_USB_ACCESSORY;
}
if (device2 == AUDIO_DEVICE_NONE) {
device2 = availableOutputDevicesType & AUDIO_DEVICE_OUT_USB_DEVICE;
}
if (device2 == AUDIO_DEVICE_NONE) {
device2 = availableOutputDevicesType & AUDIO_DEVICE_OUT_DGTL_DOCK_HEADSET;
}
if ((device2 == AUDIO_DEVICE_NONE) && (strategy != STRATEGY_SONIFICATION)) {
// no sonification on aux digital (e.g. HDMI)
device2 = availableOutputDevicesType & AUDIO_DEVICE_OUT_AUX_DIGITAL;
}
if ((device2 == AUDIO_DEVICE_NONE) &&
(mForceUse[AUDIO_POLICY_FORCE_FOR_DOCK] == AUDIO_POLICY_FORCE_ANALOG_DOCK)) {
device2 = availableOutputDevicesType & AUDIO_DEVICE_OUT_ANLG_DOCK_HEADSET;
}
if (device2 == AUDIO_DEVICE_NONE) {
device2 = availableOutputDevicesType & AUDIO_DEVICE_OUT_SPEAKER;
}
int device3 = AUDIO_DEVICE_NONE;
if (strategy == STRATEGY_MEDIA) {
// ARC, SPDIF and AUX_LINE can co-exist with others.
device3 = availableOutputDevicesType & AUDIO_DEVICE_OUT_HDMI_ARC;
device3 |= (availableOutputDevicesType & AUDIO_DEVICE_OUT_SPDIF);
device3 |= (availableOutputDevicesType & AUDIO_DEVICE_OUT_AUX_LINE);
}
device2 |= device3;
// device is DEVICE_OUT_SPEAKER if we come from case STRATEGY_SONIFICATION or
// STRATEGY_ENFORCED_AUDIBLE, AUDIO_DEVICE_NONE otherwise
device |= device2;
// If hdmi system audio mode is on, remove speaker out of output list.
if ((strategy == STRATEGY_MEDIA) &&
(mForceUse[AUDIO_POLICY_FORCE_FOR_HDMI_SYSTEM_AUDIO] ==
AUDIO_POLICY_FORCE_HDMI_SYSTEM_AUDIO_ENFORCED)) {
device &= ~AUDIO_DEVICE_OUT_SPEAKER;
}
// for STRATEGY_SONIFICATION:
// if SPEAKER was selected, and SPEAKER_SAFE is available, use SPEAKER_SAFE instead
if ((strategy == STRATEGY_SONIFICATION) &&
(device & AUDIO_DEVICE_OUT_SPEAKER) &&
(availableOutputDevicesType & AUDIO_DEVICE_OUT_SPEAKER_SAFE)) {
device |= AUDIO_DEVICE_OUT_SPEAKER_SAFE;
device &= ~AUDIO_DEVICE_OUT_SPEAKER;
}
} break;
... ...
}通过判断音频设备是否连接，及相关优先级进行添加设备或移除设备，这里可以通过自定义去完成音频输出的优先级。
常见设备的定义：
/system/media/audio/include/system/audio-base.h
enum {
AUDIO_DEVICE_NONE = 0x0u,
AUDIO_DEVICE_BIT_IN = 0x80000000u,
AUDIO_DEVICE_BIT_DEFAULT = 0x40000000u,
AUDIO_DEVICE_OUT_EARPIECE = 0x1u,
AUDIO_DEVICE_OUT_SPEAKER = 0x2u,
AUDIO_DEVICE_OUT_WIRED_HEADSET = 0x4u,
AUDIO_DEVICE_OUT_WIRED_HEADPHONE = 0x8u,
AUDIO_DEVICE_OUT_BLUETOOTH_SCO = 0x10u,
AUDIO_DEVICE_OUT_BLUETOOTH_SCO_HEADSET = 0x20u,
AUDIO_DEVICE_OUT_BLUETOOTH_SCO_CARKIT = 0x40u,
AUDIO_DEVICE_OUT_BLUETOOTH_A2DP = 0x80u,
AUDIO_DEVICE_OUT_BLUETOOTH_A2DP_HEADPHONES = 0x100u,
AUDIO_DEVICE_OUT_BLUETOOTH_A2DP_SPEAKER = 0x200u,
AUDIO_DEVICE_OUT_AUX_DIGITAL = 0x400u,
AUDIO_DEVICE_OUT_HDMI = 0x400u, // OUT_AUX_DIGITAL
AUDIO_DEVICE_OUT_ANLG_DOCK_HEADSET = 0x800u,
AUDIO_DEVICE_OUT_DGTL_DOCK_HEADSET = 0x1000u,
AUDIO_DEVICE_OUT_USB_ACCESSORY = 0x2000u,
AUDIO_DEVICE_OUT_USB_DEVICE = 0x4000u,
AUDIO_DEVICE_OUT_REMOTE_SUBMIX = 0x8000u,
AUDIO_DEVICE_OUT_TELEPHONY_TX = 0x10000u,
AUDIO_DEVICE_OUT_LINE = 0x20000u,
AUDIO_DEVICE_OUT_HDMI_ARC = 0x40000u,
AUDIO_DEVICE_OUT_SPDIF = 0x80000u,
AUDIO_DEVICE_OUT_FM = 0x100000u,
AUDIO_DEVICE_OUT_AUX_LINE = 0x200000u,
AUDIO_DEVICE_OUT_SPEAKER_SAFE = 0x400000u,
AUDIO_DEVICE_OUT_IP = 0x800000u,
AUDIO_DEVICE_OUT_BUS = 0x1000000u,
AUDIO_DEVICE_OUT_PROXY = 0x2000000u,
AUDIO_DEVICE_OUT_USB_HEADSET = 0x4000000u,
AUDIO_DEVICE_OUT_HEARING_AID = 0x8000000u,
AUDIO_DEVICE_OUT_ECHO_CANCELLER = 0x10000000u,
AUDIO_DEVICE_OUT_DEFAULT = 0x40000000u, // BIT_DEFAULT
AUDIO_DEVICE_IN_COMMUNICATION = 0x80000001u, // BIT_IN | 0x1
AUDIO_DEVICE_IN_AMBIENT = 0x80000002u, // BIT_IN | 0x2
AUDIO_DEVICE_IN_BUILTIN_MIC = 0x80000004u, // BIT_IN | 0x4
AUDIO_DEVICE_IN_BLUETOOTH_SCO_HEADSET = 0x80000008u, // BIT_IN | 0x8
AUDIO_DEVICE_IN_WIRED_HEADSET = 0x80000010u, // BIT_IN | 0x10
AUDIO_DEVICE_IN_AUX_DIGITAL = 0x80000020u, // BIT_IN | 0x20
AUDIO_DEVICE_IN_HDMI = 0x80000020u, // IN_AUX_DIGITAL
AUDIO_DEVICE_IN_VOICE_CALL = 0x80000040u, // BIT_IN | 0x40
AUDIO_DEVICE_IN_TELEPHONY_RX = 0x80000040u, // IN_VOICE_CALL
AUDIO_DEVICE_IN_BACK_MIC = 0x80000080u, // BIT_IN | 0x80
AUDIO_DEVICE_IN_REMOTE_SUBMIX = 0x80000100u, // BIT_IN | 0x100
AUDIO_DEVICE_IN_ANLG_DOCK_HEADSET = 0x80000200u, // BIT_IN | 0x200
AUDIO_DEVICE_IN_DGTL_DOCK_HEADSET = 0x80000400u, // BIT_IN | 0x400
AUDIO_DEVICE_IN_USB_ACCESSORY = 0x80000800u, // BIT_IN | 0x800
AUDIO_DEVICE_IN_USB_DEVICE = 0x80001000u, // BIT_IN | 0x1000
AUDIO_DEVICE_IN_FM_TUNER = 0x80002000u, // BIT_IN | 0x2000
AUDIO_DEVICE_IN_TV_TUNER = 0x80004000u, // BIT_IN | 0x4000
AUDIO_DEVICE_IN_LINE = 0x80008000u, // BIT_IN | 0x8000
AUDIO_DEVICE_IN_SPDIF = 0x80010000u, // BIT_IN | 0x10000
AUDIO_DEVICE_IN_BLUETOOTH_A2DP = 0x80020000u, // BIT_IN | 0x20000
AUDIO_DEVICE_IN_LOOPBACK = 0x80040000u, // BIT_IN | 0x40000
AUDIO_DEVICE_IN_IP = 0x80080000u, // BIT_IN | 0x80000
AUDIO_DEVICE_IN_BUS = 0x80100000u, // BIT_IN | 0x100000
AUDIO_DEVICE_IN_PROXY = 0x81000000u, // BIT_IN | 0x1000000
AUDIO_DEVICE_IN_USB_HEADSET = 0x82000000u, // BIT_IN | 0x2000000
AUDIO_DEVICE_IN_BLUETOOTH_BLE = 0x84000000u, // BIT_IN | 0x4000000
AUDIO_DEVICE_IN_DEFAULT = 0xC0000000u, // BIT_IN | BIT_DEFAULT
};音频输入类似，Android 9.0源码为例，不同版本会存在差异