<em>Mac</em>Book项目 2009年学校开始实施<em>Mac</em>Book项目,所有师生配备一本<em>Mac</em>Book,并同步更新了校园无线网络。学校每周进行电脑技术更新,每月发送技术支持资料,极大改变了教学及学习方式。因此2011
2021-06-01 09:32:01
Android audio音訊流資料異常問題解決分析
2022-08-30 18:00:04
一、背景
在 Android 系統的開發過程當中，音訊異常問題通常有如下幾類，無聲，調節不了聲音，爆音，聲音卡頓，聲音效果異常（忽大忽小，低音缺失等）等。
尤其聲音效果這部分問題通常從紀錄檔上資訊量較少，相對難定位根因。想要分析此類問題，便需要對聲音傳輸鏈路有一定的瞭解，能夠在鏈路中對各節點的音訊流進行採集，通過對比分析音訊流的實際效果來縮小問題範圍，找出原因。
網上已經有很多音訊框架圖和相關的大致介紹，這裡就不再贅述，只分享下音訊流的傳輸鏈路，和我們可以重點其中的哪些關鍵節點，來幫助我們快速定位問題。
二、Android Audio 音訊系統
1. 音訊鏈路
抓取音訊鏈路當中的音訊資料是分析聲音異常問題的有效方法，通過抓取不同節點的聲音資料，可以幫助我們快速定位問題發生的原因。下面先來看一張安卓官方的音訊系統框架圖：
Audio 音訊資料流整體上經過 APP，framework，hal，kernel driver四個部分，從應用端發起，不管呼叫 audio 還是 media 介面，最終還是會由 AudioTrack 將資料往下傳，經由 AudioFlinger 啟動 MixThread 或 DirectThread 等，將多個 APP 的聲音混合到一起，將聲音傳輸到 hal 層。
系統會根據音訊流型別 stream 和音訊策略 strategy 來選擇對應的 output，從而找到對應的 module，將音訊資料傳輸給 hal 層音訊庫 so 做聲音相關的處理並傳給 audio driver。
音訊流傳輸路徑圖：
從上述的音訊流流程可以看到，我們首先要確認，當前音訊流是經由哪一個 hal 層庫做處理，是 primary，usb 還是三方 so 等，然後可以在對應的節點抓取相應的音訊資訊分析。
可以根據自己的需要在音訊流的部分節點埋下相應的 dump 指令，將 pcm 寫入到相應的節點當中。
2. 音訊鏈路關鍵節點：
AudioTrack：應用寫入音訊流的起點，有 MODE_STATIC 和 MODE_STREAM 模式，通過 write 介面將資料寫入。
此節點寫入的資料是由應用層最原始的音訊資料。
AudioFlinger：負責啟動執行緒完成各個應用的混音，音訊流聲音調節等工作。裝置同時可能存在多個應用播放聲音，這時便需要將各個應用的聲音混合在一起，並且做音量的調節。
例如在車載場景中，音樂應用播放歌曲和地圖應用語音導航的聲音需要同時存在，便使用到了混音的功能，當導航語音響起時，歌曲聲音有一個明顯的變小，便可以設定音訊流的音量。
audio_hw_hal：hal 層音訊處理的入口，為 Android 原生邏輯，各廠家需要按照規範實現其中的音訊設定等介面，宣告 HAL_MODULE_INFO_SYM 結構體，實現 legacy_adev_open 方法，承接起連線 framework 和 audio driver 的作用，完成一些音效演演算法等邏輯處理。
AudioStreamOut：和 audio_hw_hal 一樣，是Android 給廠家提供的通用類，廠家在實現自己的通用庫實現時需要可以按照谷歌規範，然後在相應的音訊處理介面中實現自己的對音訊流做音效，增益等處理。
audio_hw_hal.cpp 程式碼如下，不同廠家這裡的實現略有差異，這裡只擷取部分 AOSP 原始碼。
3. 音訊庫的選擇
從音訊流傳輸路徑圖可以看到，如何找到是哪一個音訊 so 處理聲音也是至關重要的。我們知道，系統對於應用層曝光的其實只有通道型別。
舉個例子：當用戶打電話時，可以使用通話通道 STREAM_VOICE_CALL，當用戶播放視訊時，可以使用媒體通道 STREAM_MUSIC，當傳送通知時，可以使用 STREAM_NOTIFICATION。
那傳入這些通道的聲音資料，又是怎麼最終流向到具體的硬體輸出裝置呢？
以媒體通道為例，當應用層將音訊資料往 MUSIC 通道寫入時，系統便會根據 StreamType 來生成相應的
audio_attributes_t（.usage = AUDIO_USAGE_MEDIA, .content_type = AUDIO_CONTENT_TYPE_MUSIC}）
再通過 audio_attributes_t 來獲取對應的 ProductStrategy（STRATEGY_MEDIA），最後在拿到對應的 outputDevice。
Android 原生邏輯outputDevice 的選擇在 Engine.cpp 上，會具體根據當前裝置是否有接藍芽，耳機等外設，按照優先順序來選擇相應的外設裝置作為輸出，可能是耳機 （AUDIO_DEVICE_OUT_WIRED_HEADSET），聽筒（AUDIO_DEVICE_OUT_EARPIECE），喇叭（AUDIO_DEVICE_OUT_SPEAKER）等。
具體可以看 getDeviceForStrategyInt 方法。
/*
* Copyright (C) 2015 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#define LOG_TAG "APM::AudioPolicyEngine"
//#define LOG_NDEBUG 0
//#define VERY_VERBOSE_LOGGING
#ifdef VERY_VERBOSE_LOGGING
#define ALOGVV ALOGV
#else
#define ALOGVV(a...) do { } while(0)
#endif
#include "Engine.h"
#include <AudioPolicyManagerObserver.h>
#include <AudioPort.h>
#include <IOProfile.h>
#include <policy.h>
#include <utils/String8.h>
#include <utils/Log.h>
namespace android
{
namespace audio_policy
{
Engine::Engine()
: mManagerInterface(this),
mPhoneState(AUDIO_MODE_NORMAL),
mApmObserver(NULL)
{
for (int i = 0; i < AUDIO_POLICY_FORCE_USE_CNT; i++) {
mForceUse[i] = AUDIO_POLICY_FORCE_NONE;
}
}
Engine::~Engine()
{
}
void Engine::setObserver(AudioPolicyManagerObserver *observer)
{
ALOG_ASSERT(observer != NULL, "Invalid Audio Policy Manager observer");
mApmObserver = observer;
}
status_t Engine::initCheck()
{
return (mApmObserver != NULL) ? NO_ERROR : NO_INIT;
}
status_t Engine::setPhoneState(audio_mode_t state)
{
ALOGV("setPhoneState() state %d", state);
if (state < 0 || state >= AUDIO_MODE_CNT) {
ALOGW("setPhoneState() invalid state %d", state);
return BAD_VALUE;
}
if (state == mPhoneState ) {
ALOGW("setPhoneState() setting same state %d", state);
return BAD_VALUE;
}
// store previous phone state for management of sonification strategy below
int oldState = mPhoneState;
mPhoneState = state;
if (!is_state_in_call(oldState) && is_state_in_call(state)) {
ALOGV(" Entering call in setPhoneState()");
mApmObserver->getVolumeCurves().switchVolumeCurve(AUDIO_STREAM_VOICE_CALL,
AUDIO_STREAM_DTMF);
} else if (is_state_in_call(oldState) && !is_state_in_call(state)) {
ALOGV(" Exiting call in setPhoneState()");
mApmObserver->getVolumeCurves().restoreOriginVolumeCurve(AUDIO_STREAM_DTMF);
}
return NO_ERROR;
}
status_t Engine::setForceUse(audio_policy_force_use_t usage, audio_policy_forced_cfg_t config)
{
switch(usage) {
case AUDIO_POLICY_FORCE_FOR_COMMUNICATION:
if (config != AUDIO_POLICY_FORCE_SPEAKER && config != AUDIO_POLICY_FORCE_BT_SCO &&
config != AUDIO_POLICY_FORCE_NONE) {
ALOGW("setForceUse() invalid config %d for FOR_COMMUNICATION", config);
return BAD_VALUE;
}
mForceUse[usage] = config;
break;
case AUDIO_POLICY_FORCE_FOR_MEDIA:
if (config != AUDIO_POLICY_FORCE_HEADPHONES && config != AUDIO_POLICY_FORCE_BT_A2DP &&
config != AUDIO_POLICY_FORCE_WIRED_ACCESSORY &&
config != AUDIO_POLICY_FORCE_ANALOG_DOCK &&
config != AUDIO_POLICY_FORCE_DIGITAL_DOCK && config != AUDIO_POLICY_FORCE_NONE &&
config != AUDIO_POLICY_FORCE_NO_BT_A2DP && config != AUDIO_POLICY_FORCE_SPEAKER ) {
ALOGW("setForceUse() invalid config %d for FOR_MEDIA", config);
return BAD_VALUE;
}
mForceUse[usage] = config;
break;
case AUDIO_POLICY_FORCE_FOR_RECORD:
if (config != AUDIO_POLICY_FORCE_BT_SCO && config != AUDIO_POLICY_FORCE_WIRED_ACCESSORY &&
config != AUDIO_POLICY_FORCE_NONE) {
ALOGW("setForceUse() invalid config %d for FOR_RECORD", config);
return BAD_VALUE;
}
mForceUse[usage] = config;
break;
case AUDIO_POLICY_FORCE_FOR_DOCK:
if (config != AUDIO_POLICY_FORCE_NONE && config != AUDIO_POLICY_FORCE_BT_CAR_DOCK &&
config != AUDIO_POLICY_FORCE_BT_DESK_DOCK &&
config != AUDIO_POLICY_FORCE_WIRED_ACCESSORY &&
config != AUDIO_POLICY_FORCE_ANALOG_DOCK &&
config != AUDIO_POLICY_FORCE_DIGITAL_DOCK) {
ALOGW("setForceUse() invalid config %d for FOR_DOCK", config);
}
mForceUse[usage] = config;
break;
case AUDIO_POLICY_FORCE_FOR_SYSTEM:
if (config != AUDIO_POLICY_FORCE_NONE &&
config != AUDIO_POLICY_FORCE_SYSTEM_ENFORCED) {
ALOGW("setForceUse() invalid config %d for FOR_SYSTEM", config);
}
mForceUse[usage] = config;
break;
case AUDIO_POLICY_FORCE_FOR_HDMI_SYSTEM_AUDIO:
if (config != AUDIO_POLICY_FORCE_NONE &&
config != AUDIO_POLICY_FORCE_HDMI_SYSTEM_AUDIO_ENFORCED) {
ALOGW("setForceUse() invalid config %d for HDMI_SYSTEM_AUDIO", config);
}
mForceUse[usage] = config;
break;
case AUDIO_POLICY_FORCE_FOR_ENCODED_SURROUND:
if (config != AUDIO_POLICY_FORCE_NONE &&
config != AUDIO_POLICY_FORCE_ENCODED_SURROUND_NEVER &&
config != AUDIO_POLICY_FORCE_ENCODED_SURROUND_ALWAYS &&
config != AUDIO_POLICY_FORCE_ENCODED_SURROUND_MANUAL) {
ALOGW("setForceUse() invalid config %d for ENCODED_SURROUND", config);
return BAD_VALUE;
}
mForceUse[usage] = config;
break;
case AUDIO_POLICY_FORCE_FOR_VIBRATE_RINGING:
if (config != AUDIO_POLICY_FORCE_BT_SCO && config != AUDIO_POLICY_FORCE_NONE) {
ALOGW("setForceUse() invalid config %d for FOR_VIBRATE_RINGING", config);
return BAD_VALUE;
}
mForceUse[usage] = config;
break;
default:
ALOGW("setForceUse() invalid usage %d", usage);
break; // TODO return BAD_VALUE?
}
return NO_ERROR;
}
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;
}
}
routing_strategy Engine::getStrategyForUsage(audio_usage_t usage)
{
// usage to strategy mapping
switch (usage) {
case AUDIO_USAGE_ASSISTANCE_ACCESSIBILITY:
return STRATEGY_ACCESSIBILITY;
case AUDIO_USAGE_MEDIA:
case AUDIO_USAGE_GAME:
case AUDIO_USAGE_ASSISTANT:
case AUDIO_USAGE_ASSISTANCE_NAVIGATION_GUIDANCE:
case AUDIO_USAGE_ASSISTANCE_SONIFICATION:
return STRATEGY_MEDIA;
case AUDIO_USAGE_VOICE_COMMUNICATION:
return STRATEGY_PHONE;
case AUDIO_USAGE_VOICE_COMMUNICATION_SIGNALLING:
return STRATEGY_DTMF;
case AUDIO_USAGE_ALARM:
case AUDIO_USAGE_NOTIFICATION_TELEPHONY_RINGTONE:
return STRATEGY_SONIFICATION;
case AUDIO_USAGE_NOTIFICATION:
case AUDIO_USAGE_NOTIFICATION_COMMUNICATION_REQUEST:
case AUDIO_USAGE_NOTIFICATION_COMMUNICATION_INSTANT:
case AUDIO_USAGE_NOTIFICATION_COMMUNICATION_DELAYED:
case AUDIO_USAGE_NOTIFICATION_EVENT:
return STRATEGY_SONIFICATION_RESPECTFUL;
case AUDIO_USAGE_UNKNOWN:
default:
return STRATEGY_MEDIA;
}
}
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_TRANSMITTED_THROUGH_SPEAKER:
device = availableOutputDevicesType & AUDIO_DEVICE_OUT_SPEAKER;
break;
case STRATEGY_SONIFICATION_RESPECTFUL:
if (isInCall() || outputs.isStreamActiveLocally(AUDIO_STREAM_VOICE_CALL)) {
device = getDeviceForStrategyInt(
STRATEGY_SONIFICATION, availableOutputDevices, availableInputDevices, outputs,
outputDeviceTypesToIgnore);
} else {
bool media_active_locally =
outputs.isStreamActiveLocally(
AUDIO_STREAM_MUSIC, SONIFICATION_RESPECTFUL_AFTER_MUSIC_DELAY)
|| outputs.isStreamActiveLocally(
AUDIO_STREAM_ACCESSIBILITY, SONIFICATION_RESPECTFUL_AFTER_MUSIC_DELAY);
// routing is same as media without the "remote" device
device = getDeviceForStrategyInt(STRATEGY_MEDIA,
availableOutputDevices,
availableInputDevices, outputs,
AUDIO_DEVICE_OUT_REMOTE_SUBMIX | outputDeviceTypesToIgnore);
// if no media is playing on the device, check for mandatory use of "safe" speaker
// when media would have played on speaker, and the safe speaker path is available
if (!media_active_locally
&& (device & AUDIO_DEVICE_OUT_SPEAKER)
&& (availableOutputDevicesType & AUDIO_DEVICE_OUT_SPEAKER_SAFE)) {
device |= AUDIO_DEVICE_OUT_SPEAKER_SAFE;
device &= ~AUDIO_DEVICE_OUT_SPEAKER;
}
}
break;
case STRATEGY_DTMF:
if (!isInCall()) {
// when off call, DTMF strategy follows the same rules as MEDIA strategy
device = getDeviceForStrategyInt(
STRATEGY_MEDIA, availableOutputDevices, availableInputDevices, outputs,
outputDeviceTypesToIgnore);
break;
}
// when in call, DTMF and PHONE strategies follow the same rules
// FALL THROUGH
case STRATEGY_PHONE:
// Force use of only devices on primary output if:
// - in call AND
// - cannot route from voice call RX OR
// - audio HAL version is < 3.0 and TX device is on the primary HW module
if (getPhoneState() == AUDIO_MODE_IN_CALL) {
audio_devices_t txDevice = getDeviceForInputSource(AUDIO_SOURCE_VOICE_COMMUNICATION);
sp<AudioOutputDescriptor> primaryOutput = outputs.getPrimaryOutput();
audio_devices_t availPrimaryInputDevices =
availableInputDevices.getDevicesFromHwModule(primaryOutput->getModuleHandle());
// TODO: getPrimaryOutput return only devices from first module in
// audio_policy_configuration.xml, hearing aid is not there, but it's
// a primary device
// FIXME: this is not the right way of solving this problem
audio_devices_t availPrimaryOutputDevices =
(primaryOutput->supportedDevices() | AUDIO_DEVICE_OUT_HEARING_AID) &
availableOutputDevices.types();
if (((availableInputDevices.types() &
AUDIO_DEVICE_IN_TELEPHONY_RX & ~AUDIO_DEVICE_BIT_IN) == 0) ||
(((txDevice & availPrimaryInputDevices & ~AUDIO_DEVICE_BIT_IN) != 0) &&
(primaryOutput->getAudioPort()->getModuleVersionMajor() < 3))) {
availableOutputDevicesType = availPrimaryOutputDevices;
}
}
// for phone strategy, we first consider the forced use and then the available devices by
// order of priority
switch (mForceUse[AUDIO_POLICY_FORCE_FOR_COMMUNICATION]) {
case AUDIO_POLICY_FORCE_BT_SCO:
if (!isInCall() || strategy != STRATEGY_DTMF) {
device = availableOutputDevicesType & AUDIO_DEVICE_OUT_BLUETOOTH_SCO_CARKIT;
if (device) break;
}
device = availableOutputDevicesType & AUDIO_DEVICE_OUT_BLUETOOTH_SCO_HEADSET;
if (device) break;
device = availableOutputDevicesType & AUDIO_DEVICE_OUT_BLUETOOTH_SCO;
if (device) break;
// if SCO device is requested but no SCO device is available, fall back to default case
// FALL THROUGH
default: // FORCE_NONE
device = availableOutputDevicesType & AUDIO_DEVICE_OUT_HEARING_AID;
if (device) break;
// when not in a phone call, phone strategy should route STREAM_VOICE_CALL to A2DP
if (!isInCall() &&
(mForceUse[AUDIO_POLICY_FORCE_FOR_MEDIA] != AUDIO_POLICY_FORCE_NO_BT_A2DP) &&
outputs.isA2dpSupported()) {
device = availableOutputDevicesType & AUDIO_DEVICE_OUT_BLUETOOTH_A2DP;
if (device) break;
device = availableOutputDevicesType & AUDIO_DEVICE_OUT_BLUETOOTH_A2DP_HEADPHONES;
if (device) break;
}
device = availableOutputDevicesType & AUDIO_DEVICE_OUT_WIRED_HEADPHONE;
if (device) break;
device = availableOutputDevicesType & AUDIO_DEVICE_OUT_WIRED_HEADSET;
if (device) break;
device = availableOutputDevicesType & AUDIO_DEVICE_OUT_LINE;
if (device) break;
device = availableOutputDevicesType & AUDIO_DEVICE_OUT_USB_HEADSET;
if (device) break;
device = availableOutputDevicesType & AUDIO_DEVICE_OUT_USB_DEVICE;
if (device) break;
if (!isInCall()) {
device = availableOutputDevicesType & AUDIO_DEVICE_OUT_USB_ACCESSORY;
if (device) break;
device = availableOutputDevicesType & AUDIO_DEVICE_OUT_DGTL_DOCK_HEADSET;
if (device) break;
device = availableOutputDevicesType & AUDIO_DEVICE_OUT_AUX_DIGITAL;
if (device) break;
device = availableOutputDevicesType & AUDIO_DEVICE_OUT_ANLG_DOCK_HEADSET;
if (device) break;
}
device = availableOutputDevicesType & AUDIO_DEVICE_OUT_EARPIECE;
break;
case AUDIO_POLICY_FORCE_SPEAKER:
// when not in a phone call, phone strategy should route STREAM_VOICE_CALL to
// A2DP speaker when forcing to speaker output
if (!isInCall() &&
(mForceUse[AUDIO_POLICY_FORCE_FOR_MEDIA] != AUDIO_POLICY_FORCE_NO_BT_A2DP) &&
outputs.isA2dpSupported()) {
device = availableOutputDevicesType & AUDIO_DEVICE_OUT_BLUETOOTH_A2DP_SPEAKER;
if (device) break;
}
if (!isInCall()) {
device = availableOutputDevicesType & AUDIO_DEVICE_OUT_USB_ACCESSORY;
if (device) break;
device = availableOutputDevicesType & AUDIO_DEVICE_OUT_USB_DEVICE;
if (device) break;
device = availableOutputDevicesType & AUDIO_DEVICE_OUT_DGTL_DOCK_HEADSET;
if (device) break;
device = availableOutputDevicesType & AUDIO_DEVICE_OUT_AUX_DIGITAL;
if (device) break;
device = availableOutputDevicesType & AUDIO_DEVICE_OUT_ANLG_DOCK_HEADSET;
if (device) break;
}
device = availableOutputDevicesType & AUDIO_DEVICE_OUT_SPEAKER;
break;
}
break;
case STRATEGY_SONIFICATION:
// If incall, just select the STRATEGY_PHONE device: The rest of the behavior is handled by
// handleIncallSonification().
if (isInCall() || outputs.isStreamActiveLocally(AUDIO_STREAM_VOICE_CALL)) {
device = getDeviceForStrategyInt(
STRATEGY_PHONE, availableOutputDevices, availableInputDevices, outputs,
outputDeviceTypesToIgnore);
break;
}
// FALL THROUGH
case STRATEGY_ENFORCED_AUDIBLE:
// strategy STRATEGY_ENFORCED_AUDIBLE uses same routing policy as STRATEGY_SONIFICATION
// except:
// - when in call where it doesn't default to STRATEGY_PHONE behavior
// - in countries where not enforced in which case it follows STRATEGY_MEDIA
if ((strategy == STRATEGY_SONIFICATION) ||
(mForceUse[AUDIO_POLICY_FORCE_FOR_SYSTEM] == AUDIO_POLICY_FORCE_SYSTEM_ENFORCED)) {
device = availableOutputDevicesType & AUDIO_DEVICE_OUT_SPEAKER;
}
// if SCO headset is connected and we are told to use it, play ringtone over
// speaker and BT SCO
if ((availableOutputDevicesType & AUDIO_DEVICE_OUT_ALL_SCO) != 0) {
uint32_t device2 = AUDIO_DEVICE_NONE;
device2 = availableOutputDevicesType & AUDIO_DEVICE_OUT_BLUETOOTH_SCO_CARKIT;
if (device2 == AUDIO_DEVICE_NONE) {
device2 = availableOutputDevicesType & AUDIO_DEVICE_OUT_BLUETOOTH_SCO_HEADSET;
}
if (device2 == AUDIO_DEVICE_NONE) {
device2 = availableOutputDevicesType & AUDIO_DEVICE_OUT_BLUETOOTH_SCO;
}
// Use ONLY Bluetooth SCO output when ringing in vibration mode
if (!((mForceUse[AUDIO_POLICY_FORCE_FOR_SYSTEM] == AUDIO_POLICY_FORCE_SYSTEM_ENFORCED)
&& (strategy == STRATEGY_ENFORCED_AUDIBLE))) {
if (mForceUse[AUDIO_POLICY_FORCE_FOR_VIBRATE_RINGING]
== AUDIO_POLICY_FORCE_BT_SCO) {
if (device2 != AUDIO_DEVICE_NONE) {
device = device2;
break;
}
}
}
// Use both Bluetooth SCO and phone default output when ringing in normal mode
if (mForceUse[AUDIO_POLICY_FORCE_FOR_COMMUNICATION] == AUDIO_POLICY_FORCE_BT_SCO) {
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;
}
if (device2 != AUDIO_DEVICE_NONE) {
device |= device2;
break;
}
}
}
// The second device used for sonification is the same as the device used by media strategy
// FALL THROUGH
case STRATEGY_ACCESSIBILITY:
if (strategy == STRATEGY_ACCESSIBILITY) {
// do not route accessibility prompts to a digital output currently configured with a
// compressed format as they would likely not be mixed and dropped.
for (size_t i = 0; i < outputs.size(); i++) {
sp<AudioOutputDescriptor> desc = outputs.valueAt(i);
audio_devices_t devices = desc->device() &
(AUDIO_DEVICE_OUT_HDMI | AUDIO_DEVICE_OUT_SPDIF | AUDIO_DEVICE_OUT_HDMI_ARC);
if (desc->isActive() && !audio_is_linear_pcm(desc->mFormat) &&
devices != AUDIO_DEVICE_NONE) {
availableOutputDevicesType = availableOutputDevices.types() & ~devices;
}
}
availableOutputDevices =
availableOutputDevices.getDevicesFromType(availableOutputDevicesType);
if (outputs.isStreamActive(AUDIO_STREAM_RING) ||
outputs.isStreamActive(AUDIO_STREAM_ALARM)) {
return getDeviceForStrategyInt(
STRATEGY_SONIFICATION, availableOutputDevices, availableInputDevices, outputs,
outputDeviceTypesToIgnore);
}
if (isInCall()) {
return getDeviceForStrategyInt(
STRATEGY_PHONE, availableOutputDevices, availableInputDevices, outputs,
outputDeviceTypesToIgnore);
}
}
// For other cases, STRATEGY_ACCESSIBILITY behaves like STRATEGY_MEDIA
// FALL THROUGH
// FIXME: STRATEGY_REROUTING follow STRATEGY_MEDIA for now
case STRATEGY_REROUTING:
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;
default:
ALOGW("getDeviceForStrategy() unknown strategy: %d", strategy);
break;
}
if (device == AUDIO_DEVICE_NONE) {
ALOGV("getDeviceForStrategy() no device found for strategy %d", strategy);
device = mApmObserver->getDefaultOutputDevice()->type();
ALOGE_IF(device == AUDIO_DEVICE_NONE,
"getDeviceForStrategy() no default device defined");
}
ALOGVV("getDeviceForStrategy() strategy %d, device %x", strategy, device);
return device;
}
audio_devices_t Engine::getDeviceForInputSource(audio_source_t inputSource) const
{
const DeviceVector &availableOutputDevices = mApmObserver->getAvailableOutputDevices();
const DeviceVector &availableInputDevices = mApmObserver->getAvailableInputDevices();
const SwAudioOutputCollection &outputs = mApmObserver->getOutputs();
audio_devices_t availableDeviceTypes = availableInputDevices.types() & ~AUDIO_DEVICE_BIT_IN;
uint32_t device = AUDIO_DEVICE_NONE;
// when a call is active, force device selection to match source VOICE_COMMUNICATION
// for most other input sources to avoid rerouting call TX audio
if (isInCall()) {
switch (inputSource) {
case AUDIO_SOURCE_DEFAULT:
case AUDIO_SOURCE_MIC:
case AUDIO_SOURCE_VOICE_RECOGNITION:
case AUDIO_SOURCE_UNPROCESSED:
case AUDIO_SOURCE_HOTWORD:
case AUDIO_SOURCE_CAMCORDER:
inputSource = AUDIO_SOURCE_VOICE_COMMUNICATION;
break;
default:
break;
}
}
switch (inputSource) {
case AUDIO_SOURCE_VOICE_UPLINK:
if (availableDeviceTypes & AUDIO_DEVICE_IN_VOICE_CALL) {
device = AUDIO_DEVICE_IN_VOICE_CALL;
break;
}
break;
case AUDIO_SOURCE_DEFAULT:
case AUDIO_SOURCE_MIC:
if (availableDeviceTypes & AUDIO_DEVICE_IN_BLUETOOTH_A2DP) {
device = AUDIO_DEVICE_IN_BLUETOOTH_A2DP;
} else if ((mForceUse[AUDIO_POLICY_FORCE_FOR_RECORD] == AUDIO_POLICY_FORCE_BT_SCO) &&
(availableDeviceTypes & AUDIO_DEVICE_IN_BLUETOOTH_SCO_HEADSET)) {
device = AUDIO_DEVICE_IN_BLUETOOTH_SCO_HEADSET;
} else if (availableDeviceTypes & AUDIO_DEVICE_IN_WIRED_HEADSET) {
device = AUDIO_DEVICE_IN_WIRED_HEADSET;
} else if (availableDeviceTypes & AUDIO_DEVICE_IN_USB_HEADSET) {
device = AUDIO_DEVICE_IN_USB_HEADSET;
} else if (availableDeviceTypes & AUDIO_DEVICE_IN_USB_DEVICE) {
device = AUDIO_DEVICE_IN_USB_DEVICE;
} else if (availableDeviceTypes & AUDIO_DEVICE_IN_BUILTIN_MIC) {
device = AUDIO_DEVICE_IN_BUILTIN_MIC;
}
break;
case AUDIO_SOURCE_VOICE_COMMUNICATION:
// Allow only use of devices on primary input if in call and HAL does not support routing
// to voice call path.
if ((getPhoneState() == AUDIO_MODE_IN_CALL) &&
(availableOutputDevices.types() & AUDIO_DEVICE_OUT_TELEPHONY_TX) == 0) {
sp<AudioOutputDescriptor> primaryOutput = outputs.getPrimaryOutput();
availableDeviceTypes =
availableInputDevices.getDevicesFromHwModule(primaryOutput->getModuleHandle())
& ~AUDIO_DEVICE_BIT_IN;
}
switch (mForceUse[AUDIO_POLICY_FORCE_FOR_COMMUNICATION]) {
case AUDIO_POLICY_FORCE_BT_SCO:
// if SCO device is requested but no SCO device is available, fall back to default case
if (availableDeviceTypes & AUDIO_DEVICE_IN_BLUETOOTH_SCO_HEADSET) {
device = AUDIO_DEVICE_IN_BLUETOOTH_SCO_HEADSET;
break;
}
// FALL THROUGH
default: // FORCE_NONE
if (availableDeviceTypes & AUDIO_DEVICE_IN_WIRED_HEADSET) {
device = AUDIO_DEVICE_IN_WIRED_HEADSET;
} else if (availableDeviceTypes & AUDIO_DEVICE_IN_USB_HEADSET) {
device = AUDIO_DEVICE_IN_USB_HEADSET;
} else if (availableDeviceTypes & AUDIO_DEVICE_IN_USB_DEVICE) {
device = AUDIO_DEVICE_IN_USB_DEVICE;
} else if (availableDeviceTypes & AUDIO_DEVICE_IN_BUILTIN_MIC) {
device = AUDIO_DEVICE_IN_BUILTIN_MIC;
}
break;
case AUDIO_POLICY_FORCE_SPEAKER:
if (availableDeviceTypes & AUDIO_DEVICE_IN_BACK_MIC) {
device = AUDIO_DEVICE_IN_BACK_MIC;
} else if (availableDeviceTypes & AUDIO_DEVICE_IN_BUILTIN_MIC) {
device = AUDIO_DEVICE_IN_BUILTIN_MIC;
}
break;
}
break;
case AUDIO_SOURCE_VOICE_RECOGNITION:
case AUDIO_SOURCE_UNPROCESSED:
case AUDIO_SOURCE_HOTWORD:
if (mForceUse[AUDIO_POLICY_FORCE_FOR_RECORD] == AUDIO_POLICY_FORCE_BT_SCO &&
availableDeviceTypes & AUDIO_DEVICE_IN_BLUETOOTH_SCO_HEADSET) {
device = AUDIO_DEVICE_IN_BLUETOOTH_SCO_HEADSET;
} else if (availableDeviceTypes & AUDIO_DEVICE_IN_WIRED_HEADSET) {
device = AUDIO_DEVICE_IN_WIRED_HEADSET;
} else if (availableDeviceTypes & AUDIO_DEVICE_IN_USB_HEADSET) {
device = AUDIO_DEVICE_IN_USB_HEADSET;
} else if (availableDeviceTypes & AUDIO_DEVICE_IN_USB_DEVICE) {
device = AUDIO_DEVICE_IN_USB_DEVICE;
} else if (availableDeviceTypes & AUDIO_DEVICE_IN_BUILTIN_MIC) {
device = AUDIO_DEVICE_IN_BUILTIN_MIC;
}
break;
case AUDIO_SOURCE_CAMCORDER:
if (availableDeviceTypes & AUDIO_DEVICE_IN_BACK_MIC) {
device = AUDIO_DEVICE_IN_BACK_MIC;
} else if (availableDeviceTypes & AUDIO_DEVICE_IN_BUILTIN_MIC) {
device = AUDIO_DEVICE_IN_BUILTIN_MIC;
}
break;
case AUDIO_SOURCE_VOICE_DOWNLINK:
case AUDIO_SOURCE_VOICE_CALL:
if (availableDeviceTypes & AUDIO_DEVICE_IN_VOICE_CALL) {
device = AUDIO_DEVICE_IN_VOICE_CALL;
}
break;
case AUDIO_SOURCE_REMOTE_SUBMIX:
if (availableDeviceTypes & AUDIO_DEVICE_IN_REMOTE_SUBMIX) {
device = AUDIO_DEVICE_IN_REMOTE_SUBMIX;
}
break;
case AUDIO_SOURCE_FM_TUNER:
if (availableDeviceTypes & AUDIO_DEVICE_IN_FM_TUNER) {
device = AUDIO_DEVICE_IN_FM_TUNER;
}
break;
default:
ALOGW("getDeviceForInputSource() invalid input source %d", inputSource);
break;
}
if (device == AUDIO_DEVICE_NONE) {
ALOGV("getDeviceForInputSource() no device found for source %d", inputSource);
if (availableDeviceTypes & AUDIO_DEVICE_IN_STUB) {
device = AUDIO_DEVICE_IN_STUB;
}
ALOGE_IF(device == AUDIO_DEVICE_NONE,
"getDeviceForInputSource() no default device defined");
}
ALOGV("getDeviceForInputSource()input source %d, device %08x", inputSource, device);
return device;
}
template <>
AudioPolicyManagerInterface *Engine::queryInterface()
{
return &mManagerInterface;
}
} // namespace audio_policy
} // namespace android通過以上分析，我們知道了音訊會流向哪個輸出裝置，那麼下一個問題來了，是由誰負責傳輸和對音訊資料做最後的處理呢？
這裡就需要看音訊裝置的策略檔案，還是以媒體通道為例，假設裝置沒有接任何外接裝置，選擇的 outputDevice 是 AUDIO_DEVICE_OUT_SPEAKER。
接下來就要看哪個 output so 支援 AUDIO_DEVICE_OUT_SPEAKER，符合度最高的 output so 將會負責資料傳輸，最終經由 tinyalsa 寫入到 pcm 節點中。
不同的 Android 版本在組態檔上會有些許差異，可能放置在 *audio_policy_configuration.xml 中，有些在 audio_policy.conf 中。
三、案例分析
1. 聲音忽大忽小問題
具體分析
有使用者反饋使用優酷視訊播放視訊時，概率性出現聲音忽大忽小的問題，一旦出現就是在播放指定音訊時是必現的。接下來聯絡使用者幫提供裝置的紀錄檔資訊和操作步驟，按照使用者操作來複現問題，通過 demo 還原使用者環境引數便能復現。 首先分析確認發現在這個過程中聲音音量均無變化，所以初步懷疑可能是和音訊流資料出現異常有關。在上圖中數位有標識的5個點中分別抓取音訊，使用 Audacity 匯入音訊檔來進行分析，發現位置4的音訊正常，而位置5的音訊出現了聲音異常的現象。具體見下圖：
所以便可以確認在音訊資料經過 hal 層音效處理前是正常等，經過音效處理後，在某些特殊的聲音資料下，音效庫縮小了聲音的幅值，從而導致聲音的異常。
為了實錘是音效庫 so 導致的問題，通過關閉音效庫的功能，最終發現聲音忽大忽小的問題消失了。
從以上嘗試的結果綜合分析可以確認，是音效 so 庫對通道聲音進行處理時影響到了原有聲音的功能。通過修改 so 庫最終來解決這個問題。
2. 應用卡頓問題
有使用者反饋說是開啟應用A播放視訊正常，然後直接返回到 home 目錄，應用A後臺播放時會出現斷音的現象。
具體分析
聲音卡頓，錄音掉幀類的現象在聲音問題中非常常見。從現象上來看，就是使用者切換到後臺時沒有暫停播放，視訊在後臺播放時出現。老規矩，我們先分析相關 log，通過紀錄檔分析發現，當問題出現時，紀錄檔上頻繁列印 get null buffer 的資訊。
所以懷疑是否是音訊資料丟失導致的。dump 音訊資料抓取到系統混音後輸出到輸出裝置的原始音訊，可以幫助實錘上層系統傳下來的資料是否正常。於是發現位置3的音訊如下：
從抓取到的音訊可以看到，在後臺異常播放時，在該時間段內會出現明顯音訊丟幀的現象。接下來要看看是在哪一塊出現了丟幀。進一步分析 audioTrack 傳下來的資料，出現了丟失掉一部分音訊的現象，時長相當於原音訊的一半。
基於此，為了實錘是應用A傳下來的資料就有缺失，從紀錄檔資訊跟蹤，決定在 audioTrack 上加紀錄檔資訊來看，發現當切換到後臺時，audioTrack 每次還是寫 4096 個 byte ，但是寫資料的頻率降低了一半。
正常：28.600-27.546=1.054 44次 間隔 1.054/43= 0.0245秒/次。
異常：40.839-39.804=1.035 22次 間隔 1.035/21= 0.0493秒/次。
考慮到這一塊是否是和後臺程序的優先順序相關。當程序降低時導致了寫資料的執行緒能夠拿到的CPU資源變小，出現了斷音的問題。通過和其他型號的平板對比發現，各廠家 Android 10 的平板大部分均有此問題，而 android7 和 android 8 的平板就沒有這個問題。基於以上情況，更加懷疑是和 android 的特性相關，可能是新的 android 平板針對後臺執行緒優先順序做了處理，目的也很明確，就是限制後臺應用的活躍程度，來保證裝置效能。
此時進一步分析最終發現是和 TimerSlackHigh 的引數相關。
system/core/libprocessgroup/profiles/task_profiles.json：
{
"Name": "TimerSlackHigh",
"Actions": [
{
"Name": "SetTimerSlack",
"Params":
{
"Slack": "40000000"
}
}
]
},
{
"Name": "TimerSlackNormal",
"Actions": [
{
"Name": "SetTimerSlack",
"Params":
{
"Slack": "50000"
}
}
]
},
該引數影響了應用後臺執行緒 sleep/wait 之間所消耗的時間。可以看到，當應用從前臺切換到後臺時，這個時間從50 微秒上調到 40 毫秒。從而導致寫入音訊資料量大大減少。通過修改引數可以解決，但是提高後臺執行緒的活躍度，很可能影響到整體效能，因此不作處理。最終像使用者解釋，切換後臺時可以手動停止播放視訊，同時反饋給應用，由應用規範應用流程，起後臺程序來做單獨處理。
四、總結
按照以上案例，我們來總結下當聲音出現異常時一些快速定位偵錯的手段：
- 抓取位置1的音訊資料，如果該資料異常。代表從應用端傳遞下來的資料即為異常，大部分情況下為應用問題。曾經遇到一個是應用預設會將
track音量調為0，此時調節系統音量時不會有聲音的。需要使用者點選該應用內的一個靜音按鈕才有聲音，這時候就會在位置1抓到一串無聲的音訊，這種在安卓版本表現是一致的。但是也有可能是像案例2一樣和後臺優先順序有關，導致只在較高的版本上出現問題。 - 抓取位置3的音訊資料，若此音訊流經過各播放執行緒時出現問題，則可能是系統 mix， direct 邏輯出現問題，原生邏輯通常不會有問題，有可能是客製化修改引發的。
- 抓取位置5的音訊資料，此部分邏輯是由
output so來處理的，可能是音效庫處理資料等操作導致聲音異常。
以上就是Android audio音訊流資料異常問題解決分析的詳細內容，更多關於Android audio音訊流資料異常的資料請關注it145.com其它相關文章！
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