multimedia framework

Java端发起调用，MediaPlayer会转至MediaPlayerService,在mediaserver进程中创建一个client,然后通过client调用相应的解码工具解码后创建AudioTrack，所有待输出的AudioTrack在AudioFlinger::AudioMixer里合成，然后通过AudioHAL(AudioHardwareInterface的实际实现者)传至实际的硬件来实现播放

1.Java调用

MediaPlayer mp = new MediaPlayer();

mp.setDataSource(PATH_TO_FILE);

mp.prepare();

mp.start();

2.MediaPlayer调用通过binder方式在MediaPlayerService进程中创建Client；

MediaPlayer:: prepare MediaPlayer:: start 通过binder调用Client的具体实现。

status_t MediaPlayer::setDataSource(
        const char *url, const KeyedVector<String8, String8> *headers)
{
    LOGI("setDataSource(%s)", url);
    status_t err = BAD_VALUE;
    if (url != NULL) {
        const sp<IMediaPlayerService>& service(getMediaPlayerService());
        if (service != 0) {
            sp<IMediaPlayer> player(
                    service->create(getpid(), this, url, headers));
            err = setDataSource(player);
        }
    }
    return err;
}

3.MediaPlayerService实现

/*实例化Client*/

sp<IMediaPlayer> MediaPlayerService::create(
        pid_t pid, const sp<IMediaPlayerClient>& client, const char* url,
        const KeyedVector<String8, String8> *headers)
{
    int32_t connId = android_atomic_inc(&mNextConnId);
    sp<Client> c = new Client(this, pid, connId, client);
    LOGV("Create new client(%d) from pid %d, url=%s, connId=%d", connId, pid, url, connId);
    if (NO_ERROR != c->setDataSource(url, headers))
    {
        c.clear();
        return c;
    }
    wp<Client> w = c;
    Mutex::Autolock lock(mLock);
    mClients.add(w);//SortedVector< wp<Client> >  mClients;
    return c;
}

void MediaPlayerService::removeClient(wp<Client> client)
{
    Mutex::Autolock lock(mLock);
    mClients.remove(client);
}

MediaPlayerService::Client::~Client()
{
    LOGV("Client(%d) destructor pid = %d", mConnId, mPid);
    mAudioOutput.clear();
    wp<Client> client(this);
    disconnect();
    mService->removeClient(client);
}

MediaPlayerService::Client::setDataSource(...) {

....

        player_type playerType = getPlayerType(url);
        sp<MediaPlayerBase> p = createPlayer(playerType);// call android::createPlayer(playerType, this,notify);   set notify to MediaPlayer

....

}

MediaPlayerService::Client::prepareAsync；

MediaPlayerService::Client::start；

4. Awesomeplayer

void AwesomePlayer::notifyListener_l(int msg, int ext1, int ext2) {
    if (mListener != NULL) {
        sp<MediaPlayerBase> listener = mListener.promote();


        if (listener != NULL) {
            listener->sendEvent(msg, ext1, ext2);
        }
    }
}

  virtual void        sendEvent(int msg, int ext1=0, int ext2=0) { if (mNotify)mNotify(mCookie, msg, ext1, ext2); }  

                             mNotify----> void MediaPlayer::notify(int msg, int ext1, int ext2)

http://forest606.blog.163.com/blog/static/134450089201002835641104/