コグノスケ

ノートPC <--(Wi-Fi)--> 親機 <-+-(Wi-Fi)--> 子機1 <--(ギガビットイーサ)--> ファイルサーバ
                               `-(Wi-Fi)--> 子機2 <--(ギガビットイーサ)--> サブマシンなど

ノートPC <--(11ac)--> 親機 <-+-(11n)--> 子機1 <--(ギガビットイーサ)--> ファイルサーバ
                              `-(11n)--> 子機2 <--(ギガビットイーサ)--> サブマシンなど

ノートPC <--(11ac)--> 親機 <-+-(11ac 2x2 MU-MIMO)--> 子機1 <--(ギガビットイーサ)--> ファイルサーバ
                              `-(11ac 2x2 MU-MIMO)--> 子機2 <--(ギガビットイーサ)--> サブマシンなど

OpenMAXコンポーネント生成とコールバックの指定

//android/frameworks/av/media/libstagefright/omx/OMX.cpp

status_t OMX::allocateNode(
        const char *name, const sp<IOMXObserver> &observer,
        sp<IBinder> *nodeBinder, node_id *node) {

...
    
    OMXNodeInstance *instance = new OMXNodeInstance(this, observer, name); //★★1番目の引数がownerなので、thisつまりこのオブジェクトが指定される★★

    OMX_COMPONENTTYPE *handle;
    OMX_ERRORTYPE err = mMaster->makeComponentInstance(
            name, &OMXNodeInstance::kCallbacks,
            instance, &handle); //★★2番目の引数kCallbacksがコールバック関数の指定。3番目の引数instanceがFillBufferDoneのpAppDataに渡される★★


//android/frameworks/av/media/libstagefright/omx/OMXNodeInstance.cpp

// static
OMX_CALLBACKTYPE OMXNodeInstance::kCallbacks = {
    &OnEvent, &OnEmptyBufferDone, &OnFillBufferDone
};

デコード完了のコールバック処理

//android/frameworks/av/media/libstagefright/omx/OMXNodeInstance.cpp
// static
OMX_ERRORTYPE OMXNodeInstance::OnFillBufferDone(
        OMX_IN OMX_HANDLETYPE /* hComponent */,
        OMX_IN OMX_PTR pAppData,
        OMX_IN OMX_BUFFERHEADERTYPE* pBuffer) {

...

    OMXNodeInstance *instance = static_cast<OMXNodeInstance *>(pAppData); //★★makeComponentInstanceの3番目の引数に渡した値★★
    if (instance->mDying) {
        return OMX_ErrorNone;
    }
    int fenceFd = instance->retrieveFenceFromMeta_l(pBuffer, kPortIndexOutput);
    return instance->owner()->OnFillBufferDone(instance->nodeID(),
            instance->findBufferID(pBuffer), pBuffer, fenceFd); //★★ownerはOMX型のオブジェクトなのでOMX::OnFillBufferを見る★★
}


//android/frameworks/av/media/libstagefright/omx/OMX.cpp

OMX_ERRORTYPE OMX::OnFillBufferDone(
        node_id node, buffer_id buffer, OMX_IN OMX_BUFFERHEADERTYPE *pBuffer, int fenceFd) {
    ALOGV("OnFillBufferDone buffer=%p", pBuffer);

    omx_message msg;
    msg.type = omx_message::FILL_BUFFER_DONE;
    msg.node = node;
    msg.fenceFd = fenceFd;
    msg.u.extended_buffer_data.buffer = buffer;
    msg.u.extended_buffer_data.range_offset = pBuffer->nOffset;
    msg.u.extended_buffer_data.range_length = pBuffer->nFilledLen;
    msg.u.extended_buffer_data.flags = pBuffer->nFlags;
    msg.u.extended_buffer_data.timestamp = pBuffer->nTimeStamp;

    findDispatcher(node)->post(msg); //★★post() とは何だろうか？？★★

    return OMX_ErrorNone;
}

sp<OMX::CallbackDispatcher> OMX::findDispatcher(node_id node) {
    Mutex::Autolock autoLock(mLock);

    ssize_t index = mDispatchers.indexOfKey(node);

    return index < 0 ? NULL : mDispatchers.valueAt(index); //★★mDispatchersとは？★★
}

メッセージの生成

//android/frameworks/av/media/libstagefright/include/OMX.h

class OMX : public BnOMX,
            public IBinder::DeathRecipient {

...

    KeyedVector<node_id, sp<CallbackDispatcher> > mDispatchers; //★★mDispatchersの定義★★


//android/frameworks/av/media/libstagefright/omx/OMX.cpp

struct OMX::CallbackDispatcher : public RefBase {
    CallbackDispatcher(OMXNodeInstance *owner);

    // Posts |msg| to the listener's queue. If |realTime| is true, the listener thread is notified
    // that a new message is available on the queue. Otherwise, the message stays on the queue, but
    // the listener is not notified of it. It will process this message when a subsequent message
    // is posted with |realTime| set to true.
    void post(const omx_message &msg, bool realTime = true);
...

private:
...
    std::list<omx_message> mQueue;


void OMX::CallbackDispatcher::post(const omx_message &msg, bool realTime) {
    Mutex::Autolock autoLock(mLock);

    mQueue.push_back(msg); //★★メッセージをキューに追加★★
    if (realTime) {
        mQueueChanged.signal();
    }
}

メッセージの消費

//android/frameworks/av/media/libstagefright/omx/OMX.cpp

bool OMX::CallbackDispatcherThread::threadLoop() {
    return mDispatcher->loop();
}

bool OMX::CallbackDispatcher::loop() {
    for (;;) {
        std::list<omx_message> messages;

        {
            Mutex::Autolock autoLock(mLock);
            while (!mDone && mQueue.empty()) {
                mQueueChanged.wait(mLock);
            }

            if (mDone) {
                break;
            }

            messages.swap(mQueue); //★★mQueueのロック時間を短くするため、別のリストに全てのメッセージを移動させる★★
        }

        dispatch(messages); //★★メッセージ処理★★
    }

    return false;
}

void OMX::CallbackDispatcher::dispatch(std::list<omx_message> &messages) {
    if (mOwner == NULL) {
        ALOGV("Would have dispatched a message to a node that's already gone.");
        return;
    }
    mOwner->onMessages(messages); //★★メッセージ送信先のmOwnerとは？★★
}

OMX::CallbackDispatcher::CallbackDispatcher(OMXNodeInstance *owner)
    : mOwner(owner), //★★CallbackDispatcherの生成時に渡された引数で初期化されている★★
      mDone(false) {
    mThread = new CallbackDispatcherThread(this);
    mThread->run("OMXCallbackDisp", ANDROID_PRIORITY_FOREGROUND);
}

メッセージは誰に届くのか

//android/frameworks/av/media/libstagefright/omx/OMX.cpp

status_t OMX::allocateNode(
        const char *name, const sp<IOMXObserver> &observer,
        sp<IBinder> *nodeBinder, node_id *node) {

...

    OMXNodeInstance *instance = new OMXNodeInstance(this, observer, name);

    OMX_COMPONENTTYPE *handle;
    OMX_ERRORTYPE err = mMaster->makeComponentInstance(
            name, &OMXNodeInstance::kCallbacks,
            instance, &handle); //★★3番目の引数、つまりinstanceがFillBufferDoneのpAppDataに渡される★★

    if (err != OMX_ErrorNone) {
        ALOGE("FAILED to allocate omx component '%s' err=%s(%#x)", name, asString(err), err);

        instance->onGetHandleFailed();

        return StatusFromOMXError(err);
    }

    *node = makeNodeID_l(instance);
    mDispatchers.add(*node, new CallbackDispatcher(instance)); //★★メッセージの送信先を登録する★★

メッセージが届きました？

void OMXNodeInstance::onMessages(std::list<omx_message> &messages) {
    for (std::list<omx_message>::iterator it = messages.begin(); it != messages.end(); ) {
        if (handleMessage(*it)) {
            messages.erase(it++); //★★デコードに付随する情報をメッセージに載せる★★
        } else {
            ++it;
        }
    }

    if (!messages.empty()) {
        mObserver->onMessages(messages); //★★mObserverとは？★★
    }
}

observerとは？

//android/frameworks/av/media/libstagefright/include/OMXNodeInstance.h

struct OMXNodeInstance {
...
private:
...
    sp<IOMXObserver> mObserver;


//android/frameworks/av/media/libstagefright/omx/OMXNodeInstance.cpp

OMXNodeInstance::OMXNodeInstance(
        OMX *owner, const sp<IOMXObserver> &observer, const char *name)
    : mOwner(owner),
      mNodeID(0),
      mHandle(NULL),
      mObserver(observer), //★★コンストラクタの2番目の引数observerで初期化している★★
      mDying(false),
      mSailed(false),
      mQueriedProhibitedExtensions(false),
      mBufferIDCount(0)
{


//android/frameworks/av/media/libstagefright/omx/OMX.cpp

status_t OMX::allocateNode(
        const char *name, const sp<IOMXObserver> &observer,
        sp<IBinder> *nodeBinder, node_id *node) {

...

    OMXNodeInstance *instance = new OMXNodeInstance(this, observer, name); //★★allocateNodeの2番目の引数observerを渡している★★

allocateNodeのobserverにたどり着くのは大変

//android/frameworks/av/media/libstagefright/ACodec.cpp

bool ACodec::UninitializedState::onAllocateComponent(const sp<AMessage> &msg) {

...

    OMXClient client; //★★binderのクライアント★★
    if (client.connect() != OK) { //★★デコーダは別プロセスで実行されているので、接続する★★
        mCodec->signalError(OMX_ErrorUndefined, NO_INIT);
        return false;
    }

...

    sp<IOMX> omx = client.interface(); //★★binderを使って通信するためのインタフェース★★


//android/frameworks/av/media/libstagefright/OMXClient.cpp

class OMXClient {
public:
    OMXClient();

    status_t connect();
    void disconnect();

    sp<IOMX> interface() {
        return mOMX; //★★インタフェースはこれ★★
    }


//android/frameworks/av/media/libstagefright/OMXClient.cpp

status_t OMXClient::connect() {
    sp<IServiceManager> sm = defaultServiceManager();
    sp<IBinder> playerbinder = sm->getService(String16("media.player"));
    sp<IMediaPlayerService> mediaservice = interface_cast<IMediaPlayerService>(playerbinder);

...

    sp<IOMX> mediaServerOMX = mediaservice->getOMX();

...

    sp<IBinder> codecbinder = sm->getService(String16("media.codec"));
    sp<IMediaCodecService> codecservice = interface_cast<IMediaCodecService>(codecbinder);

...

    sp<IOMX> mediaCodecOMX = codecservice->getOMX();

...

    mOMX = new MuxOMX(mediaServerOMX, mediaCodecOMX); //★★インタフェースはここで設定している★★

    return OK;
}

allocateNodeのobserver

//android/frameworks/av/media/libstagefright/ACodec.cpp

bool ACodec::UninitializedState::onAllocateComponent(const sp<AMessage> &msg) {

...

    sp<IOMX> omx = client.interface(); //★★MuxOMXのオブジェクトのはず★★

...

    sp<CodecObserver> observer = new CodecObserver; //★★たぶんこれがobserver★★
    IOMX::node_id node = 0;

    status_t err = NAME_NOT_FOUND;
    for (size_t matchIndex = 0; matchIndex < matchingCodecs.size();
            ++matchIndex) {
        componentName = matchingCodecs[matchIndex];
        quirks = MediaCodecList::getQuirksFor(componentName.c_str());

        pid_t tid = gettid();
        int prevPriority = androidGetThreadPriority(tid);
        androidSetThreadPriority(tid, ANDROID_PRIORITY_FOREGROUND);
        err = omx->allocateNode(componentName.c_str(), observer, &mCodec->mNodeBinder, &node); //★★ここでobserverをMuxOMX::allocateNodeに渡す★★


//android/frameworks/av/media/libstagefright/OMXClient.cpp

status_t MuxOMX::allocateNode(
        const char *name, const sp<IOMXObserver> &observer,
        sp<IBinder> *nodeBinder,
        node_id *node) {

...

    sp<IOMX> omx;

    node_location loc = getPreferredCodecLocation(name);
    if (loc == CODECPROCESS) {
        omx = mMediaCodecOMX;
    } else if (loc == MEDIAPROCESS) {
        omx = mMediaServerOMX;
    } else {
        if (mLocalOMX == NULL) {
            mLocalOMX = new OMX;
        }
        omx = mLocalOMX;
    }

    status_t err = omx->allocateNode(name, observer, nodeBinder, node); //★★OMX::allocateNode() などに渡す★★
    ALOGV("allocated node_id %x on %s OMX", *node, omx == mMediaCodecOMX ? "codecprocess" :
            omx == mMediaServerOMX ? "mediaserver" : "local");

やっと来たobserver

//android/frameworks/av/media/libstagefright/ACodec.cpp

struct CodecObserver : public BnOMXObserver {

...

    // from IOMXObserver
    virtual void onMessages(const std::list<omx_message> &messages) {
...

        sp<AMessage> notify = mNotify->dup();
        bool first = true;
        sp<MessageList> msgList = new MessageList();
        for (std::list<omx_message>::const_iterator it = messages.cbegin();
              it != messages.cend(); ++it) {
            const omx_message &omx_msg = *it;
            if (first) {
                notify->setInt32("node", omx_msg.node);
                first = false;
            }

            sp<AMessage> msg = new AMessage;
            //★★omx_msg.typeはOMX::OnFillBufferDone() にてFILL_BUFFER_DONEに設定★★
            msg->setInt32("type", omx_msg.type);
            switch (omx_msg.type) {
...
                case omx_message::FILL_BUFFER_DONE:
                {
                    //★★omx_messageからAMessageに変換している★★
                    msg->setInt32(
                            "buffer", omx_msg.u.extended_buffer_data.buffer);
                    msg->setInt32(
                            "range_offset",
                            omx_msg.u.extended_buffer_data.range_offset);
                    msg->setInt32(
                            "range_length",
                            omx_msg.u.extended_buffer_data.range_length);
                    msg->setInt32(
                            "flags",
                            omx_msg.u.extended_buffer_data.flags);
                    msg->setInt64(
                            "timestamp",
                            omx_msg.u.extended_buffer_data.timestamp);
                    msg->setInt32(
                            "fence_fd", omx_msg.fenceFd);
                    break;
                }
...
            }
            msgList->getList().push_back(msg);
        }
        notify->setObject("messages", msgList);
        notify->post(); //★★notifyとは？？★★
    }

今度はnotify

//android/frameworks/av/media/libstagefright/ACodec.cpp

struct CodecObserver : public BnOMXObserver {
...

    void setNotificationMessage(const sp<AMessage> &msg) {
        mNotify = msg;
    }


bool ACodec::UninitializedState::onAllocateComponent(const sp<AMessage> &msg) {

...

    sp<CodecObserver> observer = new CodecObserver;
    IOMX::node_id node = 0;

...

    status_t err = NAME_NOT_FOUND;
    for (size_t matchIndex = 0; matchIndex < matchingCodecs.size();
            ++matchIndex) {
        componentName = matchingCodecs[matchIndex];
        quirks = MediaCodecList::getQuirksFor(componentName.c_str());

        pid_t tid = gettid();
        int prevPriority = androidGetThreadPriority(tid);
        androidSetThreadPriority(tid, ANDROID_PRIORITY_FOREGROUND);
        err = omx->allocateNode(componentName.c_str(), observer, &mCodec->mNodeBinder, &node); //★★11月7日の日記参照★★

...

    notify = new AMessage(kWhatOMXMessageList, mCodec);
    observer->setNotificationMessage(notify); //★★ここで設定している★★

今度はAMessage

//android/frameworks/av/media/libstagefright/foundation/AMessage.cpp

status_t AMessage::post(int64_t delayUs) {
    sp<ALooper> looper = mLooper.promote();
    if (looper == NULL) {
        ALOGW("failed to post message as target looper for handler %d is gone.", mTarget);
        return -ENOENT;
    }

    looper->post(this, delayUs); //★★たらい回し再び、mLooperとは？★★
    return OK;
}

...

AMessage::AMessage(uint32_t what, const sp<const AHandler> &handler)
    : mWhat(what),
      mNumItems(0) {
    setTarget(handler); //★★mLooperはここから設定★★
}

...

void AMessage::setTarget(const sp<const AHandler> &handler) {
    if (handler == NULL) {
        mTarget = 0;
        mHandler.clear();
        mLooper.clear();
    } else {
        mTarget = handler->id();
        mHandler = handler->getHandler();
        mLooper = handler->getLooper(); //★★mLooperはAMessageコンストラクタの2番目の引数のgetLooper() が返す値★★
    }
}