android 声卡音频策略小记

5.1 以前应该是在 hardware/libhardware_legacy/audio/AudioPolicyManagerBase.cpp

5.1 的时候

Android5.1/frameworks/av/services/audiopolicy/

比如调节 USB 和 HEADPHONE，甚至 HDMI 的声音输出顺序。

这个要根据 stream type 来选不同的 device ..在优先级别方面调整其顺序就行了。

如在没有强制设置成某device 的情况下，headphone 的优先级最高: headphone > usb sound card

--- a/frameworks/av/services/audiopolicy/AudioPolicyManager.cpp
+++ b/frameworks/av/services/audiopolicy/AudioPolicyManager.cpp
@@ -4725,12 +4725,13 @@ audio_devices_t AudioPolicyManager::getDeviceForStrategy(routing_strategy strate
device = availableOutputDeviceTypes & AUDIO_DEVICE_OUT_BLUETOOTH_A2DP_HEADPHONES;
if (device) break;
}
+ //edit Wade usb > headphone when call
+ device = availableOutputDeviceTypes & AUDIO_DEVICE_OUT_USB_DEVICE;
+ if (device) break;
device = availableOutputDeviceTypes & AUDIO_DEVICE_OUT_WIRED_HEADPHONE;
if (device) break;
device = availableOutputDeviceTypes & AUDIO_DEVICE_OUT_WIRED_HEADSET;
if (device) break;
- device = availableOutputDeviceTypes & AUDIO_DEVICE_OUT_USB_DEVICE;
- if (device) break;
if (mPhoneState != AUDIO_MODE_IN_CALL) {
device = availableOutputDeviceTypes & AUDIO_DEVICE_OUT_USB_ACCESSORY;
if (device) break;

以上的调整为USB 的优先级高于耳机: usb sound card > headphone

在某些特殊的场景，可能会用到。

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