Android12 MultiMedia框架之NuPlayerDriver

最新推荐文章于 2025-04-11 15:47:45 发布

Leaf Ye

最新推荐文章于 2025-04-11 15:47:45 发布

阅读量952

点赞数 21

分类专栏： Android Native MultiMedia 文章标签： android

本文链接：https://blog.youkuaiyun.com/yzq_yezhiqiang/article/details/139509398

版权

Android 同时被 3 个专栏收录

24 篇文章

订阅专栏

Native

11 篇文章

订阅专栏

MultiMedia

10 篇文章

订阅专栏

目录：Android12 MultiMedia框架

NuPlayerDriver的创建也是在setDataSource()中发生的，那么我们继续前文分析，这次我们换个本地播放的setDataSource()方法来看看，稍微简单点：

//frameworks/av/media/libmedia/mediaplayer.cpp  
status_t MediaPlayer::setDataSource(int fd, int64_t offset, int64_t length)  
{  
    ALOGV("setDataSource(%d, %" PRId64 ", %" PRId64 ")", fd, offset, length);  
  
    status_t err = UNKNOWN_ERROR;  
    const sp<IMediaPlayerService> service(getMediaPlayerService());  
    if (service != 0) {  
        sp<IMediaPlayer> player(service->create(this, mAudioSessionId, mAttributionSource));  
        if ((NO_ERROR != doSetRetransmitEndpoint(player)) ||  
            (NO_ERROR != player->setDataSource(fd, offset, length))) {  
            player.clear();  
        }  
        err = attachNewPlayer(player);  
    }  
  
    return err;  
}

create()前文已经看过了，接着看今天的正题：

//frameworks/av/media/libmediaplayerservice/MediaPlayerService.cpp  
status_t MediaPlayerService::Client::setDataSource(int fd, int64_t offset, int64_t length)  
{  
    ALOGV("setDataSource fd=%d (%s), offset=%lld, length=%lld",  
            fd, nameForFd(fd).c_str(), (long long) offset, (long long) length);  
    struct stat sb;  
    int ret = fstat(fd, &sb);  
    //省略  
  
    if (offset >= sb.st_size) {  
        ALOGE("offset error");  
        return UNKNOWN_ERROR;  
    }  
    if (offset + length > sb.st_size) {  
        length = sb.st_size - offset;  
        ALOGV("calculated length = %lld", (long long)length);  
    }  
  
    player_type playerType = MediaPlayerFactory::getPlayerType(this,  
                                                               fd,  
                                                               offset,  
                                                               length);  
    sp<MediaPlayerBase> p = setDataSource_pre(playerType);  
    if (p == NULL) {  
        return NO_INIT;  
    }  
  
    // now set data source  
    return mStatus = setDataSource_post(p, p->setDataSource(fd, offset, length));  
}

先通过getPlayerType()方法来确定player的类型（其实在当前版本中，只有一种player：NU_PLAYER类型），我们来看看getPlayerType()的原理是啥：

//frameworks/av/media/libmediaplayerservice/MediaPlayerFactory.cpp  
player_type MediaPlayerFactory::getPlayerType(const sp<IMediaPlayer>& client,  
                                              int fd,  
                                              int64_t offset,  
                                              int64_t length) {  
    GET_PLAYER_TYPE_IMPL(client, fd, offset, length);  
}  
  
#define GET_PLAYER_TYPE_IMPL(a...)                      \  
    Mutex::Autolock lock_(&sLock);                      \  
                                                        \  
    player_type ret = STAGEFRIGHT_PLAYER;               \  
    float bestScore = 0.0;                              \  
                                                        \  
    for (size_t i = 0; i < sFactoryMap.size(); ++i) {   \  
                                                        \  
        IFactory* v = sFactoryMap.valueAt(i);           \  
        float thisScore;                                \  
        CHECK(v != NULL);                               \  
        thisScore = v->scoreFactory(a, bestScore);      \  
        if (thisScore > bestScore) {                    \  
            ret = sFactoryMap.keyAt(i);                 \  
            bestScore = thisScore;                      \  
        }                                               \  
    }                                                   \  
                                                        \  
    if (0.0 == bestScore) {                             \  
        ret = getDefaultPlayerType();                   \  
    }                                                   \  
                                                        \  
    return ret;

这段代码定义了一个宏 GET_PLAYER_TYPE_IMPL，用于确定最佳播放器类型。这个宏的作用是在多个工厂对象中选择得分最高的播放器类型。设计这个宏的人估计喜欢打球。

在讲MediaPlayerService章节的时候，其实有一个player没讲，即：TEST_PLAYER。sFactoryMap里面存储了两个Factory类型：NuPlayerFactory和TestPlayerFactory，看名字就知道后者是测试用的。而这两个Factory都没有实现本地播放类型的scoreFactory()方法，所以它的返回值就是父类的初始实现的值：0.0。所以最终返回的还是getDefaultPlayerType()类型：NU_PLAYER。话说回来，当前Android12版本只保留了NU_PLAYER类型，根本不需要这一通分析，哈哈。

那么，继续看setDataSource_pre()方法在操办什么大事情：

//frameworks/av/media/libmediaplayerservice/MediaPlayerService.cpp  
sp<MediaPlayerBase> MediaPlayerService::Client::setDataSource_pre(  
        player_type playerType)  
{  
    ALOGV("player type = %d", playerType);  
  
    // create the right type of player  
    sp<MediaPlayerBase> p = createPlayer(playerType);  
    if (p == NULL) {  
        return p;  
    }  
  
    //监听三个服务的死亡情况：media.extractor服务、OMX服务、Codec2服务  
    //省略  
  
    mAudioDeviceUpdatedListener = new AudioDeviceUpdatedNotifier(p);  
  
    if (!p->hardwareOutput()) {  
        mAudioOutput = new AudioOutput(mAudioSessionId, mAttributionSource,  
                mAudioAttributes, mAudioDeviceUpdatedListener);  
        static_cast<MediaPlayerInterface*>(p.get())->setAudioSink(mAudioOutput);  
    }  
  
    return p;  
}

这段代码里应题的内容都在createPlayer()内，死亡通知我直接省略了，AudioOutput不是本次的主题也不看了。我们来看看createPlayer()的实现吧：

//frameworks/av/media/libmediaplayerservice/MediaPlayerService.cpp  
sp<MediaPlayerBase> MediaPlayerService::Client::createPlayer(player_type playerType)  
{  
    // determine if we have the right player type  
    sp<MediaPlayerBase> p = getPlayer();  
    if ((p != NULL) && (p->playerType() != playerType)) {  
        ALOGV("delete player");  
        p.clear();  
    }  
    if (p == NULL) {  
        p = MediaPlayerFactory::createPlayer(playerType, mListener,  
            VALUE_OR_FATAL(aidl2legacy_int32_t_pid_t(mAttributionSource.pid)));  
    }  
  
    if (p != NULL) {  
        p->setUID(VALUE_OR_FATAL(aidl2legacy_int32_t_uid_t(mAttributionSource.uid)));  
    }  
  
    return p;  
}  
  
//frameworks/av/media/libmediaplayerservice/MediaPlayerFactory.cpp  
sp<MediaPlayerBase> MediaPlayerFactory::createPlayer(  
        player_type playerType,  
        const sp<MediaPlayerBase::Listener> &listener,  
        pid_t pid) {  
    sp<MediaPlayerBase> p;  
    IFactory* factory;  
    status_t init_result;  
    Mutex::Autolock lock_(&sLock);  
  
    if (sFactoryMap.indexOfKey(playerType) < 0) {  
        ALOGE("Failed to create player object of type %d, no registered"  
              " factory", playerType);  
        return p;  
    }  
  
    factory = sFactoryMap.valueFor(playerType);  
    CHECK(NULL != factory);  
    p = factory->createPlayer(pid);  
  
    if (p == NULL) {  
        ALOGE("Failed to create player object of type %d, create failed",  
               playerType);  
        return p;  
    }  
  
    init_result = p->initCheck();  
    if (init_result == NO_ERROR) {  
        p->setNotifyCallback(listener);  
    } else {  
        ALOGE("Failed to create player object of type %d, initCheck failed"  
              " (res = %d)", playerType, init_result);  
        p.clear();  
    }  
  
    return p;  
}

第一次进createPlayer()必然会调用MediaPlayerFactory::createPlayer()，根据player_type从sFactoryMap中取出Factory，这里就进入了NuPlayerFactory的createPlayer()方法：

//frameworks/av/media/libmediaplayerservice/MediaPlayerFactory.cpp
virtual sp<MediaPlayerBase> createPlayer(pid_t pid) {
	ALOGV(" create NuPlayer");
	return new NuPlayerDriver(pid);
}

今天的主角来了，此处直接new了一个NuPlayerDriver：

//frameworks/av/media/libmediaplayerservice/nuplayer/NuPlayerDriver.cpp
NuPlayerDriver::NuPlayerDriver(pid_t pid)
    : mState(STATE_IDLE),
      mIsAsyncPrepare(false),
      mAsyncResult(UNKNOWN_ERROR),
      mSetSurfaceInProgress(false),
      mDurationUs(-1),
      mPositionUs(-1),
      mSeekInProgress(false),
      mPlayingTimeUs(0),
      mRebufferingTimeUs(0),
      mRebufferingEvents(0),
      mRebufferingAtExit(false),
      mLooper(new ALooper),
      mMediaClock(new MediaClock),
      mPlayer(new NuPlayer(pid, mMediaClock)),
      mPlayerFlags(0),
      mMetricsItem(NULL),
      mClientUid(-1),
      mAtEOS(false),
      mLooping(false),
      mAutoLoop(false) {
    ALOGD("NuPlayerDriver(%p) created, clientPid(%d)", this, pid);
    mLooper->setName("NuPlayerDriver Looper");

    mMediaClock->init();

    // set up an analytics record
    mMetricsItem = mediametrics::Item::create(kKeyPlayer);

    mLooper->start(
            false, /* runOnCallingThread */
            true,  /* canCallJava */
            PRIORITY_AUDIO);

    mLooper->registerHandler(mPlayer);

    mPlayer->init(this);
}

看其构造函数还是一目了然的，分别创建了ALooper、MediaClock和Nuplayer并做一些初始化操作。这里就不挨个分析了，我直接把new NuPlayerDriver()生成的内容以图的方法展现出来：

本来想把所有的模块画在一起，但是因为连线的原因不好处理，连接的乱七八糟，怎么调整都不好看，所以干脆就分割成了几个小块，也就是图中的3个小方框。需要注意的是：颜色相同的模块是同一个实例，大家自行在脑海里去把他们连接成一个整体。

值得一提的是：NuPlayerDriver中已经把NuPlayer的消息通知机制（ALooper/AHandler/AMessage，AMessage是随用随创建的）给建立起来了。这个消息通知机制我将在下一章节来分析。

回过头来，创建完NuPlayerDriver以后，调用setNotifyCallback()将Client构造时（参见：Android12 MultiMedia框架之MediaPlayerService::Client）创建的Listener保存到它的父类MediaPlayerBase的mListener成员中。

至此，setDataSource_pre()分析结束。接下来进入setDataSource_post()了，它的第二个参数传入的是NuPlayerDriver的setDataSource()的执行结果，这个函数就是在创建source了，我们后面的章节再看，这里跳过。setDataSource_post()其实就是将创建的NuPlayerDriver保存到mPlayer。

最后，来整体看下执行完MediaPlayer的setDataSource()后，生成的大概的框图是什么样子的：