Android MultiMedia框架——mediaserver启动

Posted 2022-11-22 VNanyesheshou

基于Andorid9.0源码

一 mediaserver进程

mediaserver进程由mediaserver.rc文件启动

mediaserver.rc文件

service media /system/bin/mediaserver
    class main
    user media
    group audio camera inet net_bt net_bt_admin net_bw_acct drmrpc mediadrm
    ioprio rt 4
    writepid /dev/cpuset/foreground/tasks /dev/stune/foreground/tasks

目录frameworks/av/media/mediaserver

main_mediaserver.cpp对应入口，main函数

int main(int argc __unused, char **argv __unused)

    signal(SIGPIPE, SIG_IGN);

    sp<ProcessState> proc(ProcessState::self());
    sp<IServiceManager> sm(defaultServiceManager());
    ALOGI("ServiceManager: %p", sm.get());
    InitializeIcuOrDie();
    MediaPlayerService::instantiate();
    ResourceManagerService::instantiate();
    registerExtensions();
    ProcessState::self()->startThreadPool();
    IPCThreadState::self()->joinThreadPool();

• 创建ProcessState对象，开启binder驱动，分配内存供后续传输数据；
• 创建IServiceManager对象。通过这个对象，可以与servicemanager进行跨进程通信。
• InitializeIcuOrDie 初始化icu， icu是对应icu4C国际化库
• 创建MediaPlayerService，并初始化
• 创建并初始化ResourceManagerService
• startThreadPool -》启动binder线程池
• joinThreadPool-》把主线程加入到线程池中

二 MediaPlayerService

MediaPlayerService该服务负责管理MediaRecorder和MediaPlayer的创建、销毁，具体录像和播放由MediaRecorderClient、MediaPlayerService::Client等实现

目录frameworks/av/media/libmediaplayerservice/

void MediaPlayerService::instantiate() 
    defaultServiceManager()->addService(
            String16("media.player"), new MediaPlayerService());


MediaPlayerService::MediaPlayerService()

    mNextConnId = 1;
    MediaPlayerFactory::registerBuiltinFactories();

MediaPlayerService::instantiate过程

• 创建MediaPlayerService对象；
• 将服务注册到ServiceManager中，服务名称为“media.player”，便于其他进程使用该服务；

接着看MediaPlayerFactory::registerBuiltinFactories()

void MediaPlayerFactory::registerBuiltinFactories() 
    Mutex::Autolock lock_(&sLock);
    if (sInitComplete)
        return;

    IFactory* factory = new NuPlayerFactory();
    if (registerFactory_l(factory, NU_PLAYER) != OK)
        delete factory;
    factory = new TestPlayerFactory();
    if (registerFactory_l(factory, TEST_PLAYER) != OK)
        delete factory;

    sInitComplete = true;

创建NuPlayerFactory、TestPlayerFactory对象，分别添加注册到FactoryMap中。

NuPlayerFactory、TestPlayerFactory工厂类，用于创建Player