C
keyConfig {
 keyList = ["power", "VolUp", "VolDown", "Up", "Down", "Left", "Right"];
 keyInfoList {
 key1 {
 match_attr = "key_device0";
 /* 0:touch 1:key 2:keyboard 3:mouse 4:button 5:crown 6:encoder */
 inputType = 1;
 keyName = "power";
 gpioNum = 1;
 irqFlag = 3;
 debounceTime = 80;
 }
 key2 {
 keyName = "volUp";
 gpioNum = 31;
 irqFlag = 1;
 debounceTime = 80;
 }
 key3 {
 keyName = "volDown";
 gpioNum = 32;
 irqFlag = 1;
 debounceTime = 80;
 }
 }
 }

在openHarmony中KEY与多模输入的简单关系图。

OpenHarmony3.1 按下音量按键后Audio service发生的哪些事

结合音频组件架构图，AudioPolicy主要完成Audio设备、音量等管理工作。

++
AudioPolicyServer完成依赖模块的加载，音量按键的调节与多模输入模块相关。
void AudioPolicyServer::OnAddSystemAbility(int32_t systemAbilityId, const std::string& deviceId)
{
 switch (systemAbilityId) {
 case MULTIMODAL_INPUT_SERVICE_ID: // 3101
 ......
 SubscribeKeyEvents();
 break;
 ......
 }
}

OpenHarmony3.1 按下音量按键后Audio service发生的哪些事

2.SubscribeKeyEvents接口完成Vol+/Vol-按键事件的订阅，当前Input事件触发后会执行对应的动作。

C++
void AudioPolicyServer::SubscribeKeyEvents()
{
 // 按键信息配置
 MMI::InputManager *im = MMI::InputManager::GetInstance();
 std::set<int32_t> preKeys;
 std::shared_ptr<OHOS::MMI::KeyOption> keyOption_down = std::make_shared<OHOS::MMI::KeyOption>();
 keyOption_down->SetPreKeys(preKeys);
 keyOption_down->SetFinalKey(OHOS::MMI::KeyEvent::KEYCODE_VOLUME_DOWN);
 keyOption_down->SetFinalKeyDown(true);
 keyOption_down->SetFinalKeyDownDuration(0);
 // key触发的事件
 im->SubscribeKeyEvent(keyOption_down, [=](std::shared_ptr<MMI::KeyEvent> keyEventCallBack) {
 std::lock_guard<std::mutex> lock(volumeKeyEventMutex_);
 AudioStreamType streamInFocus = GetStreamInFocus();
 if (streamInFocus == AudioStreamType::STREAM_DEFAULT) {
 streamInFocus = AudioStreamType::STREAM_MUSIC;
 }
 // 获取当前音量
 float currentVolume = GetStreamVolume(streamInFocus);
 if (ConvertVolumeToInt(currentVolume) <= MIN_VOLUME_LEVEL) {
 for (auto it = volumeChangeCbsMap_.begin(); it != volumeChangeCbsMap_.end(); ++it) {
 std::shared_ptr<VolumeKeyEventCallback> volumeChangeCb = it->second;
 if (volumeChangeCb == nullptr) {
 MEDIA_ERR_LOG("volumeChangeCb: nullptr for client : %{public}d", it->first);
 continue;
 }
 volumeChangeCb->OnVolumeKeyEvent(streamInFocus, MIN_VOLUME_LEVEL, true);
 }
 return;
 }
 // 设置音量
 SetStreamVolume(streamInFocus, currentVolume-GetVolumeFactor(), true);
 });

1.接着上述订阅事件，AudioPolicyServer通过调用AudioPolicyService类，AudioPolicyService继而调用AudioAdapterManager::SetStreamVolume。

此接口中，通过完成WriteVolumeToKvStore音量值的保存(kv:Key,value)，继而调用AudioServiceAdapter::mAudioServiceAdapter->SetVolume(streamType, volume);进行音量设置。

2.AudioServiceAdapter::SetVolume接口。

PulseAudio作为Audio服务，SetVolume通过调用PulseAudio的接口完成音量设置。

C++
int32_t PulseAudioServiceAdapterImpl::SetVolume(AudioStreamType streamType, float volume)
{
 ......
 pa_threaded_mainloop_lock(mMainLoop);
 pa_operation *operation = pa_context_get_sink_input_info_list(mContext,
 PulseAudioServiceAdapterImpl::PaGetSinkInputInfoVolumeCb, reinterpret_cast<void*>(userData.get()));
 ......
 return SUCCESS;
}

此接口中PaGetSinkInputInfoVolumeCb作为回调函数，通过pa_context_set_sink_input_volume接口完成音量设置的具体工作。

C++
void PulseAudioServiceAdapterImpl::PaGetSinkInputInfoVolumeCb(pa_context *c, const pa_sink_input_info *i, int eol,void *userdata)
{
 ......
 pa_cvolume cv = i->volume;
 uint32_t volume = pa_sw_volume_from_linear(vol);
 pa_cvolume_set(&cv, i->channel_map.channels, volume);
 pa_operation_unref(pa_context_set_sink_input_volume(c, i->index, &cv, NULL, NULL));
 ......
 return;
}

上述类之间的关系见图，如下：

OpenHarmony3.1 按下音量按键后Audio service发生的哪些事

1.module-hdi-sink/module-hdi-source(foundation/multimedia/audio_standard/frameworks/native/pulseaudio/src/modules/hdi)作为PulseAudio的module，系统启动过程被audiopolicy进程加载启动。

2.renderer_sink_adapter(foundation/multimedia/audio_standard/frameworks/native/audiorenderer/src/renderer_sink_adapter.c) 作为hdi-sink和renderer之间的适配层，完成接口封装与定义。

C++
struct RendererSinkAdapter {
 int32_t (*RendererSinkInit)(const SinkAttr *attr);
 void (*RendererSinkDeInit)(void);
 int32_t (*RendererSinkStart)(void);
 int32_t (*RendererSinkStop)(void);
 int32_t (*RendererRenderFrame)(char *data, uint64_t len, uint64_t *writeLen);
 int32_t (*RendererSinkSetVolume)(float left, float right);
 int32_t (*RendererSinkGetLatency)(uint32_t *latency);
};

其中RendererSinkSetVolume接口完成音量设置，LoadSinkAdapter接口根据不同的设备类型，给出不同的接口实现。

C++
int32_t LoadSinkAdapter(const char *device, struct RendererSinkAdapter **sinkAdapter)
{
 ......
 if (!strcmp(device, g_deviceClassPrimary)) {
 MEDIA_INFO_LOG("%{public}s: primary device", __func__);
 ......
 adapter->RendererSinkSetVolume = AudioRendererSinkSetVolume;
 ......
 g_deviceClass = CLASS_TYPE_PRIMARY;
 } else if (!strcmp(device, g_deviceClassA2Dp)) {
 MEDIA_INFO_LOG("%{public}s: a2dp device", __func__);
 ......
 adapter->RendererSinkSetVolume = BluetoothRendererSinkSetVolume;
 ......
 g_deviceClass = CLASS_TYPE_A2DP;
 } else {
 MEDIA_ERR_LOG("%{public}s: Device not supported", __func__);
 free(adapter);
 return ERROR;
 }
 ......
}

3.RendererSinkSetVolume如何与HDI接口对接。

以primary device为例，RendererSinkSetVolume对应的实现为AudioRendererSinkSetVolume，调用g_audioRendrSinkInstance->SetVolume，即AudioRendererSink::SetVolume接口。

C++
int32_t AudioRendererSink::SetVolume(float left, float right)
{
 ......
 ret = audioRender_->volume.SetVolume(reinterpret_cast<AudioHandle>(audioRender_), volume);
 if (ret) {
 MEDIA_ERR_LOG("AudioRendererSink::Set volume failed!");
 }
 return ret;
}