audio

Android4.1 中出现了一个新的类，BinderService,所有的Native Service 都会继承这个类。

class BinderService
{
public:
    static status_t publish(bool allowIsolated = false) {
        sp<IServiceManager> sm(defaultServiceManager());
        return sm->addService(String16(SERVICE::getServiceName()), new SERVICE(), allowIsolated);
    }

    static void publishAndJoinThreadPool(bool allowIsolated = false) {
        sp<IServiceManager> sm(defaultServiceManager());
        sm->addService(String16(SERVICE::getServiceName()), new SERVICE(), allowIsolated);
        ProcessState::self()->startThreadPool();
        IPCThreadState::self()->joinThreadPool();
    }

    static void instantiate() { publish(); }

    static status_t shutdown() {
        return NO_ERROR;
    }
}

从代码中可以得知，这个类的publish(),就是将Native Service 注册到ServiceManager,同时 BinderService 作为 NativeService 的友元类。这是因为BinderService 需要访问 Native Service 的getServiceName方法。

class AudioPolicyService :
    public BinderService<AudioPolicyService>,
    public BnAudioPolicyService,
    public IBinder::DeathRecipient

AudioPolicyService继承了BinderService接口，用于把AudioPolicyService本地服务注册到ServiceManager中；
AudioPolicyService继承了BnAudioPolicyService接口，这样AudioPolicyService就可以基于Android的Binder机制，做为服务器向外部提供服务；
AudioPolicyService有一个内部线程类AudioCommandThread，顾名思义，所有的命令（音量控制，输入、输出的切换等）最终都会在该线程中排队执行；

namespace {
    struct audio_policy_service_ops aps_ops = {
        open_output           : aps_open_output,
        open_duplicate_output : aps_open_dup_output,
        close_output          : aps_close_output,
        suspend_output        : aps_suspend_output,
        restore_output        : aps_restore_output,
        open_input            : aps_open_input,
        close_input           : aps_close_input,
        set_stream_volume     : aps_set_stream_volume,
        set_stream_output     : aps_set_stream_output,
        set_parameters        : aps_set_parameters,
        get_parameters        : aps_get_parameters,
        start_tone            : aps_start_tone,
        stop_tone             : aps_stop_tone,
        set_voice_volume      : aps_set_voice_volume,
        move_effects          : aps_move_effects,
        load_hw_module        : aps_load_hw_module,
        open_output_on_module : aps_open_output_on_module,
        open_input_on_module  : aps_open_input_on_module,
    };
}

aps_ops：主要是通过IAudioFlinger，调用AudioSystem中的接口 

 

\frameworks\av\services\audioflinger\AudioPolicyService.cpp

AudioPolicyService::AudioPolicyService()
    : BnAudioPolicyService() , mpAudioPolicyDev(NULL) , mpAudioPolicy(NULL)
{
    char value[PROPERTY_VALUE_MAX];
    const struct hw_module_t *module;
    int forced_val;
    int rc;

    Mutex::Autolock _l(mLock);

    // start tone playback thread
    mTonePlaybackThread = new AudioCommandThread(String8(""));
    // start audio commands thread
    mAudioCommandThread = new AudioCommandThread(String8("ApmCommand"));

    /* instantiate the audio policy manager */
    rc = hw_get_module(AUDIO_POLICY_HARDWARE_MODULE_ID, &module);
    rc = audio_policy_dev_open(module, &mpAudioPolicyDev);
    rc = mpAudioPolicyDev->create_audio_policy(mpAudioPolicyDev, &aps_ops, this,
                                               &mpAudioPolicy);
    rc = mpAudioPolicy->init_check(mpAudioPolicy);
    // load audio pre processing modules
    if (access(AUDIO_EFFECT_VENDOR_CONFIG_FILE, R_OK) == 0) {
        loadPreProcessorConfig(AUDIO_EFFECT_VENDOR_CONFIG_FILE);
    } else if (access(AUDIO_EFFECT_DEFAULT_CONFIG_FILE, R_OK) == 0) {
        loadPreProcessorConfig(AUDIO_EFFECT_DEFAULT_CONFIG_FILE);
    }
} 

\hardware\libhardware_legacy\audio\audio_policy_hal.cpp

struct legacy_ap_module HAL_MODULE_INFO_SYM = {
    module: {
        common: {
            tag: HARDWARE_MODULE_TAG,
            version_major: 1,
            version_minor: 0,
            id: AUDIO_POLICY_HARDWARE_MODULE_ID,
            name: "LEGACY Audio Policy HAL",
            author: "The Android Open Source Project",
            methods: &legacy_ap_module_methods,
            dso : NULL,
            reserved : {0},
        },
    },
};
static int create_legacy_ap(const struct audio_policy_device *device,
                            struct audio_policy_service_ops *aps_ops,
                            void *service,
                            struct audio_policy **ap)
{
    struct legacy_audio_policy *lap;
    int ret;

    if (!service || !aps_ops)
        return -EINVAL;

    lap = (struct legacy_audio_policy *)calloc(1, sizeof(*lap));
    if (!lap)
        return -ENOMEM;

    lap->policy.set_device_connection_state = ap_set_device_connection_state;
    lap->policy.get_device_connection_state = ap_get_device_connection_state;
    lap->policy.set_phone_state = ap_set_phone_state;
    lap->policy.set_ringer_mode = ap_set_ringer_mode;
    lap->policy.set_force_use = ap_set_force_use;
    lap->policy.get_force_use = ap_get_force_use;
    lap->policy.set_can_mute_enforced_audible =
        ap_set_can_mute_enforced_audible;
    lap->policy.init_check = ap_init_check;
    lap->policy.get_output = ap_get_output;
    lap->policy.start_output = ap_start_output;
    lap->policy.stop_output = ap_stop_output;
    lap->policy.release_output = ap_release_output;
    lap->policy.get_input = ap_get_input;
    lap->policy.start_input = ap_start_input;
    lap->policy.stop_input = ap_stop_input;
    lap->policy.release_input = ap_release_input;
    lap->policy.init_stream_volume = ap_init_stream_volume;
    lap->policy.set_stream_volume_index = ap_set_stream_volume_index;
    lap->policy.get_stream_volume_index = ap_get_stream_volume_index;
    lap->policy.set_stream_volume_index_for_device = ap_set_stream_volume_index_for_device;
    lap->policy.get_stream_volume_index_for_device = ap_get_stream_volume_index_for_device;
    lap->policy.get_strategy_for_stream = ap_get_strategy_for_stream;
    lap->policy.get_devices_for_stream = ap_get_devices_for_stream;
    lap->policy.get_output_for_effect = ap_get_output_for_effect;
    lap->policy.register_effect = ap_register_effect;
    lap->policy.unregister_effect = ap_unregister_effect;
    lap->policy.set_effect_enabled = ap_set_effect_enabled;
    lap->policy.is_stream_active = ap_is_stream_active;
    lap->policy.is_source_active = ap_is_source_active;
    lap->policy.dump = ap_dump;

    lap->service = service;
    lap->aps_ops = aps_ops;
    lap->service_client =
        new AudioPolicyCompatClient(aps_ops, service);/* 创建 */
    if (!lap->service_client) {
        ret = -ENOMEM;
        goto err_new_compat_client;
    }

    lap->apm = createAudioPolicyManager(lap->service_client);
    if (!lap->apm) {
        ret = -ENOMEM;
        goto err_create_apm;
    }

    *ap = &lap->policy;
    return 0;

err_create_apm:
    delete lap->service_client;
err_new_compat_client:
    free(lap);
    *ap = NULL;
    return ret;
}
create_legacy_ap:主要是创建了AudioPolicyCompatClient，并将它做为参数创建AudioPolicyManager。

frameworks/av/services/audioflinger/AudioPolicyCompatClient.h

AudioPolicyCompatClient(struct audio_policy_service_ops *serviceOps, void *service) :
            mServiceOps(serviceOps)
 AudioPolicyCompatClient的serviceOps指向AudioPolicyService的aps_ops

Android4.1 中出现了一个新的类，BinderService,所有的Native Service 都会继承这个类。、

 

Android4.1 中出现了一个新的类，BinderService,所有的Native Service 都会继承这个类。

Android4.1 中出现了一个新的类，BinderService,所有的Native Service 都会继承这个类。

Android4.1 中出现了一个新的类，BinderService,所有的Native Service 都会继承这个类。

Android4.1 中出现了一个新的类，BinderService,所有的Native Service 都会继承这个类。

Android4.1 中出现了一个新的类，BinderService,所有的Native Service 都会继承这个类。