【Android Audio】Parameter Framework - pfw
Parameter Framework - Android AudioPolicy Engine
使用 libaudiopolicyengineconfigurable.so 来取缔默认安卓音频引擎 libaudiopolicyenginedefault.so，因为默认安卓音频引擎是通过代码来决定策略，然而 libaudiopolicyengineconfigurable 采用读取pfw类型的文件来实现音频策略配置。
1. 优势
不需要修改代码，直接修改pfw配置文件就可以修改音频策略
2. 启用Parameter framework
-
Android U之前的版本
-
在
audio_policy_configuration.xml文件中globalConfiguration字段增加字段：engine_library="configurable"
-
Android U之后的版本
-
使用aidl的hal，读取config的时候检测
audio_policy_engine_criterion_types.xml和audio_policy_engine_criteria.xml文件存在就会启用
hardware\interfaces\audio\aidl\default\EngineConfigXmlConverter.cpp
void EngineConfigXmlConverter::init() {
...
if (getXsdcConfig()->hasCriteria() && getXsdcConfig()->hasCriterion_types()) {
AudioHalEngineConfig::CapSpecificConfig capSpecificConfig;
capSpecificConfig.criteriaV2 =
std::make_optional<>(VALUE_OR_FATAL((convertCapCriteriaCollectionToAidl(
getXsdcConfig()->getCriteria(), getXsdcConfig()->getCriterion_types()))));
...
3. 功能
当前主要是3大配置
3.1 输入（input_sources）
device_for_input_source.pfw
不同的audio_source_t使用什么样的输入设备
3.2 输出设备优先级（product_strategies）
device_for_product_strategy_phone.pfw、device_for_product_strategy_media.pfw…
不同的product_strategy_t使用什么样的输出设备
3.3 音量曲线切换（streams）
volumes.pfw
不同的audio_stream_type_t使用哪个stream type的音量曲线
eg: system的stream可以使用music的音量曲线
4. 配置pfw文件
4.1 supDomain
- supDomain定义是对Strategy进行分类命名，可以任意修改
- 可以定义多级supDomain，生成的xml中是以"."分隔
（eg： DeviceForProductStrategy.Media）
supDomain: DeviceForProductStrategy
supDomain: Media
domain: Device1
conf: ForceUseBtA2dpSpeaker
AvailableOutputDevices Includes BLUETOOTH_A2DP_SPEAKER
ForceUseForMedia Is BT_A2DP
component: /Policy/policy/product_strategies/vx_1005/selected_output_devices/mask
speaker = 0
spdif = 0
bluetooth_a2dp_speaker = 1
...
4.2 domain
- supDomain下面可以配置多个domain
- 多个domain的device是共存的
- 同一supDomain中不同的domain中不能配置相同的device
eg：下面Assistant的Strategy中配置了2个domain（Device1、Device2），ARC可以跟其他device共存
supDomain: DeviceForProductStrategy
supDomain: Assistant
domain: Device1
conf: RemoteSubmix
AvailableOutputDevices Includes REMOTE_SUBMIX
AvailableOutputDevicesAddresses Includes 0
component: /Policy/policy/product_strategies/assistant/selected_output_devices/mask
speaker = 0
remote_submix = 1
...
domain: Device2
#
# these following domains consists in device(s) that can co-exist with others
# e.g. ARC, SPDIF, AUX_LINE
#
conf: Selected
AvailableOutputDevices Includes HDMI_ARC
component: /Policy/policy/product_strategies/assistant/selected_output_devices/mask
hdmi_arc = 1
conf: NotSelected
component: /Policy/policy/product_strategies/assistant/selected_output_devices/mask
hdmi_arc = 0
...
4.3 config
- 每一个domain下面的config相当于代码中的switch-case语句。放在前面的config先被执行到。
- 满足config条件才会被使用，之后不再执行同一domain下的config。如果不满足条件则进行下一个config条件检查。
domain: Device1
conf: ForceUseBtA2dpSpeaker
AvailableOutputDevices Includes BLUETOOTH_A2DP_SPEAKER
ForceUseForMedia Is BT_A2DP
component: /Policy/policy/product_strategies/vx_1005/selected_output_devices/mask
speaker = 0
spdif = 0
hdmi = 0
hdmi_arc = 0
bluetooth_a2dp_speaker = 1
usb_device = 0
conf: UsbDevice
AvailableOutputDevices Includes USB_DEVICE
component: /Policy/policy/product_strategies/vx_1005/selected_output_devices/mask
speaker = 0
spdif = 0
hdmi = 0
hdmi_arc = 0
bluetooth_a2dp_speaker = 0
usb_device = 1
4.3.1 criterion （准则/标准）
每个criterion 定义: pfw中所有能使用的准则类型 audio_policy_engine_criteria.xml
frameworks/av/services/audiopolicy/engineconfigurable/config/example/common/audio_policy_engine_criteria.xml
4.3.2 每个criterion的值：每个准则类型的值
/vendor/etc/audio_policy_engine_criteria.xml是audio_policy_engine_criterion_typespython脚本根据audio_policy_engine_criterion_types.xml.in文件自动生成。
- Android 16使用Google最新的
capBuildPolicyCriterionTypes.py，之前安卓版本使用buildPolicyCriterionTypes.py的Python脚本。
frameworks/av/services/audiopolicy/engineconfigurable/tools/
frameworks/av/services/audiopolicy/engineconfigurable/config/example/common/audio_policy_engine_criterion_types.xml.in
...
...
4.3.3 使用criterion
例如：配置输出设备策略
conf: UsbDevice
AvailableOutputDevices Includes USB_DEVICE
AvailableOutputDevices Excludes WIRED_HEADPHONE
ANY
ForceUseForCommunication Is BT_SCO
ALL
ForceUseForCommunication Is SPEAKER
TelephonyMode IsNot IN_CALL
component: /Policy/policy/product_strategies/vx_1000/selected_output_devices/mask
...
usb_accessory = 0
usb_device = 1
usb_headset = 0
speaker = 0
...
上面的config转化为伪代码的case：
if (AvailableOutputDevices 存在 USB_DEVICE) {
if (AvailableOutputDevices 不存在 WIRED_HEADPHONE) {
if (ForceUseForCommunication == BT_SCO ||
(ForceUseForCommunication == SPEAKER && TelephonyMode != IN_CALL)) {
return USB_DEVICE;
}
}
}
当前Google pfw支持3个SubSystem（Stream、InputSource、ProductStrategy）
frameworks\av\services\audiopolicy\engineconfigurable\parameter-framework\plugin\PolicySubsystem.cpp
// Provide creators to upper layer
addSubsystemObjectFactory(
new TSubsystemObjectFactory(
mStreamComponentName,
(1 << MappingKeyName))
);
addSubsystemObjectFactory(
new TSubsystemObjectFactory(
mInputSourceComponentName,
(1 << MappingKeyName))
);
addSubsystemObjectFactory(
new TSubsystemObjectFactory(
mProductStrategyComponentName, (1 << MappingKeyName))
);
分别通过下面3个函数推送到Engine中
frameworks\av\services\audiopolicy\engineconfigurable\parameter-framework\plugin\
/vendor/etc/parameter-framework/Structure/Policy/PolicySubsystem-CommonTypes.xml
5.1 快速debug
修改完对应的pfw文件之后
parameter framework的pfw所在路径下mm -j，将/vendor/etc/parameter-framework/目录替换到平台即可