Audio笔记之MediaPlayerService:setDataSource

//下面是一个典型的播放序列：
MediaPlayer player=new MediaPlayer()
player->setDataSource(url,header);
player->prepare();
player->start();
...
//使用MediaPlayerServcie的Client对象设置数据源
status_t MediaPlayer::setDataSource(
        const char *url, const KeyedVector<String8, String8> *headers)
{
    ALOGV("setDataSource(%s)", url);
    status_t err = BAD_VALUE;
    if (url != NULL) {
        //1、获得MediaPlayerService
        const sp<IMediaPlayerService>& service(getMediaPlayerService());
        if (service != 0) {
            //2、返回MediaPlayerService的Client对象player，并保存在Service的数组对象中，
            //后续使用该Client将向MediaPlayer提供服务，因此每个MediaPlayer都对应一个Client
            sp<IMediaPlayer> player(service->create(this, mAudioSessionId));
            //3、选择正确的播放器，并设置播放器的数据源
            if ((NO_ERROR != doSetRetransmitEndpoint(player)) ||
                (NO_ERROR != player->setDataSource(url, headers))) {
                player.clear();
            }
            //4、保存最新的Client对象，断开之前Client对象
            err = attachNewPlayer(player);
        }
    }
    return err;
}
1、获取MeidaPlayerSercie
/*static*/const sp<IMediaPlayerService>&
IMediaDeathNotifier::getMediaPlayerService()
{
    ALOGV("getMediaPlayerService");
    Mutex::Autolock _l(sServiceLock);
    if (sMediaPlayerService == 0) {
        //获得BpServiceManager对象
        sp<IServiceManager> sm = defaultServiceManager();
        sp<IBinder> binder;
        do {
            binder = sm->getService(String16("media.player"));
            if (binder != 0) {
                break;
            }
            ALOGW("Media player service not published, waiting...");
            usleep(500000); // 0.5 s
        } while (true);

        if (sDeathNotifier == NULL) {
        sDeathNotifier = new DeathNotifier();
    }
    //通过Bind获取BpMediaPlayerService对象
    binder->linkToDeath(sDeathNotifier);
    sMediaPlayerService = interface_cast<IMediaPlayerService>(binder);
    }
    ALOGE_IF(sMediaPlayerService == 0, "no media player service!?");
    return sMediaPlayerService;
}
2、构造MediaPlayerService的Client对象
sp<IMediaPlayer> MediaPlayerService::create(const sp<IMediaPlayerClient>& client,
        int audioSessionId)
{
    pid_t pid = IPCThreadState::self()->getCallingPid();
    int32_t connId = android_atomic_inc(&mNextConnId);

    sp<Client> c = new Client(
            this, pid, connId, client, audioSessionId,
            IPCThreadState::self()->getCallingUid());

    ALOGV("Create new client(%d) from pid %d, uid %d, ", connId, pid,
         IPCThreadState::self()->getCallingUid());

    wp<Client> w = c;
    {
        Mutex::Autolock lock(mLock);
        mClients.add(w);
    }
    return c;
}
//保存Client端的AudioSessionId等信息
MediaPlayerService::Client::Client(
        const sp<MediaPlayerService>& service, pid_t pid,
        int32_t connId, const sp<IMediaPlayerClient>& client,
        int audioSessionId, uid_t uid)
{
    ALOGV("Client(%d) constructor", connId);
    mPid = pid;
    mConnId = connId;
    mService = service;
    mClient = client;
    mLoop = false;
    mStatus = NO_INIT;
    mAudioSessionId = audioSessionId;
    mUID = uid;
    mRetransmitEndpointValid = false;

#if CALLBACK_ANTAGONIZER
    ALOGD("create Antagonizer");
    mAntagonizer = new Antagonizer(notify, this);
#endif
}
//通过url获取对应的播放器，然后保存该播放器，并设置播放器的数据源
status_t MediaPlayerService::Client::setDataSource(
        const char *url, const KeyedVector<String8, String8> *headers)
{
    ALOGV("setDataSource(%s)", url);
    if (url == NULL)
        return UNKNOWN_ERROR;

    if ((strncmp(url, "http://", 7) == 0) ||
        (strncmp(url, "https://", 8) == 0) ||
        (strncmp(url, "rtsp://", 7) == 0)) {
        if (!checkPermission("android.permission.INTERNET")) {
            return PERMISSION_DENIED;
        }
    }

    if (strncmp(url, "content://", 10) == 0) {
        // get a filedescriptor for the content Uri and
        // pass it to the setDataSource(fd) method

        String16 url16(url);
        int fd = android::openContentProviderFile(url16);
        if (fd < 0)
        {
            ALOGE("Couldn't open fd for %s", url);
            return UNKNOWN_ERROR;
        }
        setDataSource(fd, 0, 0x7fffffffffLL); // this sets mStatus
        close(fd);
        return mStatus;
    } else {
        //通过url获取对应的播放器
        player_type playerType = MediaPlayerFactory::getPlayerType(this, url);
        sp<MediaPlayerBase> p = setDataSource_pre(playerType);
        if (p == NULL) {
            return NO_INIT;
        }

        setDataSource_post(p, p->setDataSource(url, headers));
        return mStatus;
    }
}
//通过播放器工厂的scoreFactory函数判断该播放器是否合适，选择播放器类型
#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;

player_type MediaPlayerFactory::getPlayerType(const sp<IMediaPlayer>& client,
                                              const char* url) {
    GET_PLAYER_TYPE_IMPL(client, url);
}
//这里如果所有播放器都不合适，则选择默认播放器这里流程是，
//从播放器仓库中选取最佳播放器，通过scoreFactory来确定
player_type MediaPlayerFactory::getDefaultPlayerType() {
    char value[PROPERTY_VALUE_MAX];
    if (property_get("media.stagefright.use-nuplayer", value, NULL)
            && (!strcmp("1", value) || !strcasecmp("true", value))) {
        return NU_PLAYER;
    }

    return STAGEFRIGHT_PLAYER;
}

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;
    }
    //根据AudioSessionId设置播放器的输出端
    if (!p->hardwareOutput()) {
        mAudioOutput = new AudioOutput(mAudioSessionId);
        static_cast<MediaPlayerInterface*>(p.get())->setAudioSink(mAudioOutput);
    }

    return p;
}
sp<MediaPlayerBase> MediaPlayerService::Client::createPlayer(player_type playerType)
{
    // determine if we have the right player type
    sp<MediaPlayerBase> p = mPlayer;
    if ((p != NULL) && (p->playerType() != playerType)) {
        ALOGV("delete player");
        p.clear();
    }
    if (p == NULL) {
        p = MediaPlayerFactory::createPlayer(playerType, this, notify);
    }

    if (p != NULL) {
        p->setUID(mUID);
    }

    return p;
}
//主要是创建播放器

//上面看具体StagefrightPlayerFactory 实现的时候，代码中实现了createPlayer，此处就是调用的此方法

//因此等价于return (new StagefrightPlayer()) ;
void MediaPlayerService::Client::setDataSource_post(
        const sp<MediaPlayerBase>& p,
        status_t status)
{
    ALOGV(" setDataSource");
    mStatus = status;
    if (mStatus != OK) {
        ALOGE("  error: %d", mStatus);
        return;
    }

    // Set the re-transmission endpoint if one was chosen.
    if (mRetransmitEndpointValid) {
        mStatus = p->setRetransmitEndpoint(&mRetransmitEndpoint);
        if (mStatus != NO_ERROR) {
            ALOGE("setRetransmitEndpoint error: %d", mStatus);
        }
    }

    if (mStatus == OK) {
        mPlayer = p;
    }
}
//setDataSource_post(p, p->setDataSource(source))
//设置播放器的数据源，因为实际的视屏播放是由该播放器完成
status_t StagefrightPlayer::setDataSource(
        const char *url, const KeyedVector<String8, String8> *headers) {
    return mPlayer->setDataSource(url, headers);
}
status_t AwesomePlayer::setDataSource(
        const char *uri, const KeyedVector<String8, String8> *headers) {
    Mutex::Autolock autoLock(mLock);
    return setDataSource_l(uri, headers);
}
status_t AwesomePlayer::setDataSource_l(
        const char *uri, const KeyedVector<String8, String8> *headers) {
    reset_l();

    mUri = uri;

    if (headers) {
        mUriHeaders = *headers;

        ssize_t index = mUriHeaders.indexOfKey(String8("x-hide-urls-from-log"));
        if (index >= 0) {
            // Browser is in "incognito" mode, suppress logging URLs.

            // This isn't something that should be passed to the server.
            mUriHeaders.removeItemsAt(index);

            modifyFlags(INCOGNITO, SET);
        }
    }

    ALOGI("setDataSource_l(URL suppressed)");

    // The actual work will be done during preparation in the call to
    // ::finishSetDataSource_l to avoid blocking the calling thread in
    // setDataSource for any significant time.

    {
        Mutex::Autolock autoLock(mStatsLock);
        mStats.mFd = -1;
        mStats.mURI = mUri;
    }

    return OK;
}
//4、保存新的MediaPlayerService的Client对象，并断开之前的Client和Service
status_t MediaPlayer::attachNewPlayer(const sp<IMediaPlayer>& player)
{
    status_t err = UNKNOWN_ERROR;
    sp<IMediaPlayer> p;
    { // scope for the lock
        Mutex::Autolock _l(mLock);

        if ( !( (mCurrentState & MEDIA_PLAYER_IDLE) ||
                (mCurrentState == MEDIA_PLAYER_STATE_ERROR ) ) ) {
            ALOGE("attachNewPlayer called in state %d", mCurrentState);
            return INVALID_OPERATION;
        }
        //重置相关参数
        clear_l();
        p = mPlayer;
        mPlayer = player;//更新Client属性
        if (player != 0) {
            mCurrentState = MEDIA_PLAYER_INITIALIZED;
            err = NO_ERROR;
        } else {
            ALOGE("Unable to create media player");
        }
    }
    //断开之前的Client
    if (p != 0) {
        p->disconnect();
    }

    return err;
}
// always call with lock held
void MediaPlayer::clear_l()
{
    mCurrentPosition = -1;
    mSeekPosition = -1;
    mVideoWidth = mVideoHeight = 0;
    mRetransmitEndpointValid = false;
}
void MediaPlayerService::Client::disconnect()
{
    ALOGV("disconnect(%d) from pid %d", mConnId, mPid);
    // grab local reference and clear main reference to prevent future
    // access to object
    sp<MediaPlayerBase> p;
    {
        Mutex::Autolock l(mLock);
        p = mPlayer;//播放器对象，如StagefrightPlayer
        mClient.clear();//MdediaPlayer对象
    }

    mPlayer.clear();

    // clear the notification to prevent callbacks to dead client
    // and reset the player. We assume the player will serialize
    // access to itself if necessary.
    if (p != 0) {
        p->setNotifyCallback(0, 0);
#if CALLBACK_ANTAGONIZER
        ALOGD("kill Antagonizer");
        mAntagonizer->kill();
#endif
        p->reset();//调用具体播放器的reset函数，如
    }

    disconnectNativeWindow();

    IPCThreadState::self()->flushCommands();
}
void MediaPlayerService::Client::disconnectNativeWindow() {
    if (mConnectedWindow != NULL) {
        status_t err = native_window_api_disconnect(mConnectedWindow.get(),
                NATIVE_WINDOW_API_MEDIA);

        if (err != OK) {
            ALOGW("native_window_api_disconnect returned an error: %s (%d)",
                    strerror(-err), err);
        }
    }
    mConnectedWindow.clear();
}
status_t StagefrightPlayer::reset() {
    ALOGV("reset");

    mPlayer->reset();

    return OK;
}
//具体的reset操作，不同的播放器有不同的实现
void AwesomePlayer::reset_l() {
    mVideoRenderingStarted = false;
    mActiveAudioTrackIndex = -1;
    mDisplayWidth = 0;
    mDisplayHeight = 0;

    if (mDecryptHandle != NULL) {
            mDrmManagerClient->setPlaybackStatus(mDecryptHandle,
                    Playback::STOP, 0);
            mDecryptHandle = NULL;
            mDrmManagerClient = NULL;
    }

    if (mFlags & PLAYING) {
        uint32_t params = IMediaPlayerService::kBatteryDataTrackDecoder;
        if ((mAudioSource != NULL) && (mAudioSource != mAudioTrack)) {
            params |= IMediaPlayerService::kBatteryDataTrackAudio;
        }
        if (mVideoSource != NULL) {
            params |= IMediaPlayerService::kBatteryDataTrackVideo;
        }
        addBatteryData(params);
    }

    if (mFlags & PREPARING) {
        modifyFlags(PREPARE_CANCELLED, SET);
        if (mConnectingDataSource != NULL) {
            ALOGI("interrupting the connection process");
            mConnectingDataSource->disconnect();
        }

        if (mFlags & PREPARING_CONNECTED) {
            // We are basically done preparing, we're just buffering
            // enough data to start playback, we can safely interrupt that.
            finishAsyncPrepare_l();
        }
    }

    while (mFlags & PREPARING) {
        mPreparedCondition.wait(mLock);
    }

    cancelPlayerEvents();

    mWVMExtractor.clear();
    mCachedSource.clear();
    mAudioTrack.clear();
    mVideoTrack.clear();
    mExtractor.clear();

    // Shutdown audio first, so that the respone to the reset request
    // appears to happen instantaneously as far as the user is concerned
    // If we did this later, audio would continue playing while we
    // shutdown the video-related resources and the player appear to
    // not be as responsive to a reset request.
    if ((mAudioPlayer == NULL || !(mFlags & AUDIOPLAYER_STARTED))
            && mAudioSource != NULL) {
        // If we had an audio player, it would have effectively
        // taken possession of the audio source and stopped it when
        // _it_ is stopped. Otherwise this is still our responsibility.
        mAudioSource->stop();
    }
    mAudioSource.clear();

    mTimeSource = NULL;

    delete mAudioPlayer;
    mAudioPlayer = NULL;

    if (mTextDriver != NULL) {
        delete mTextDriver;
        mTextDriver = NULL;
    }

    mVideoRenderer.clear();

    if (mVideoSource != NULL) {
        shutdownVideoDecoder_l();
    }

    mDurationUs = -1;
    modifyFlags(0, ASSIGN);
    mExtractorFlags = 0;
    mTimeSourceDeltaUs = 0;
    mVideoTimeUs = 0;

    mSeeking = NO_SEEK;
    mSeekNotificationSent = true;
    mSeekTimeUs = 0;

    mUri.setTo("");
    mUriHeaders.clear();

    mFileSource.clear();

    mBitrate = -1;
    mLastVideoTimeUs = -1;

    {
        Mutex::Autolock autoLock(mStatsLock);
        mStats.mFd = -1;
        mStats.mURI = String8();
        mStats.mBitrate = -1;
        mStats.mAudioTrackIndex = -1;
        mStats.mVideoTrackIndex = -1;
        mStats.mNumVideoFramesDecoded = 0;
        mStats.mNumVideoFramesDropped = 0;
        mStats.mVideoWidth = -1;
        mStats.mVideoHeight = -1;
        mStats.mFlags = 0;
        mStats.mTracks.clear();
    }

    mWatchForAudioSeekComplete = false;
    mWatchForAudioEOS = false;
}

以上调用流程：

MediaPlayer(JAVA层)->MediaPlayer(C层)->Client->MediaPlayService->StagefrightPlayer->AwesomePlayer

最终所有对应具体文件的操作都需要AwesomePlayer落实，如：

prepare

play

pause

总结下几种播放器的区别

StagefrightPlayer： 默认播放器，本地文件基本都使用其播放

NuPlayerDriver：主要用于播放网络视频,http https rtsp等

SonivoxPlayer：用于播放midi等类型的音乐