内存、分配-OMXCodec源码分析---part2-by小雨

查了好多资料，发现还是不全，干脆自己整理吧，至少保证在我的做法正确的，以免误导读者，也是给自己做个记录吧！

    书接前文

    omxcodec创立完了当前，前面就要开始读取数据，码解，送出数据一系列的作操

    接着看initvideodecoder，create omxcodec当前，调用了strat法方，代码如下

{
    CODEC_LOGV("OMXCodec::start ");
    Mutex::Autolock autoLock(mLock);

    if (mState != LOADED) {
        return UNKNOWN_ERROR;
    }

    sp<MetaData> params = new MetaData;
    if (mQuirks & kWantsNALFragments) {
        params->setInt32(kKeyWantsNALFragments, true);
    }
    if (meta) {
        int64_t startTimeUs = 0;
        int64_t timeUs;
        if (meta->findInt64(kKeyTime, &timeUs)) {
            startTimeUs = timeUs;
        }
        params->setInt64(kKeyTime, startTimeUs);
    }
    status_t err = mSource->start(params.get());

    if (err != OK) {
        return err;
    }

    mCodecSpecificDataIndex = 0;
    mInitialBufferSubmit = true;
    mSignalledEOS = false;
    mNoMoreOutputData = false;
    mOutputPortSettingsHaveChanged = false;
    mSeekTimeUs = -1;
    mSeekMode = ReadOptions::SEEK_CLOSEST_SYNC;
    mTargetTimeUs = -1;
    mFilledBuffers.clear();
    mPaused = false;

    err = init();
    if (err != OK) {
        ALOGV("init failed, so stop source");
        mSource->stop();
    }
    return err;
}

    初始化一些参数，init数函接着看

{
    // mLock is held.

    CHECK_EQ((int)mState, (int)LOADED);

    status_t err;
    if (!(mQuirks & kRequiresLoadedToIdleAfterAllocation)) {
        err = mOMX->sendCommand(mNode, OMX_CommandStateSet, OMX_StateIdle);
        setState(LOADED_TO_IDLE);
    }

    err = allocateBuffers();
    if (err != (status_t)OK) {
        return err;
    }

    if (mQuirks & kRequiresLoadedToIdleAfterAllocation) {
        err = mOMX->sendCommand(mNode, OMX_CommandStateSet, OMX_StateIdle);
        CHECK_EQ(err, (status_t)OK);

        setState(LOADED_TO_IDLE);
    }

    while (mState != EXECUTING && mState != ERROR) {
		mAsyncCompletion.wait(mLock);
    }
    return mState == ERROR ? UNKNOWN_ERROR : OK;
}

    omxcodec有一些状态的换转，然后就是allocateBuffers这个数函了

{
    if (mNativeWindow != NULL && portIndex == kPortIndexOutput) {
        return allocateOutputBuffersFromNativeWindow();
    }

    if ((mFlags & kEnableGrallocUsageProtected) && portIndex == kPortIndexOutput) {
        ALOGE("protected output buffers must be stent to an ANativeWindow");
        return PERMISSION_DENIED;
    }

    status_t err = OK;
    if ((mFlags & kStoreMetaDataInVideoBuffers)
            && portIndex == kPortIndexInput) {
        err = mOMX->storeMetaDataInBuffers(mNode, kPortIndexInput, OMX_TRUE);
        if (err != OK) {
            ALOGE("Storing meta data in video buffers is not supported");
            return err;
        }
    }

    OMX_PARAM_PORTDEFINITIONTYPE def;
    InitOMXParams(&def);
    def.nPortIndex = portIndex;

    err = mOMX->getParameter(
            mNode, OMX_IndexParamPortDefinition, &def, sizeof(def));

    if (err != OK) {
        return err;
    }


    size_t totalSize = def.nBufferCountActual * def.nBufferSize;
    mDealer[portIndex] = new MemoryDealer(totalSize, "OMXCodec");

    for (OMX_U32 i = 0; i < def.nBufferCountActual; ++i) {
        sp<IMemory> mem = mDealer[portIndex]->allocate(def.nBufferSize);
        CHECK(mem.get() != NULL);

        BufferInfo info;
        info.mData = NULL;
        info.mSize = def.nBufferSize;

        IOMX::buffer_id buffer;
        if (portIndex == kPortIndexInput
                && ((mQuirks & kRequiresAllocateBufferOnInputPorts)
                    || (mFlags & kUseSecureInputBuffers))) {
            if (mOMXLivesLocally) {
                mem.clear();

                err = mOMX->allocateBuffer(
                        mNode, portIndex, def.nBufferSize, &buffer,
                        &info.mData);
            } else {
                err = mOMX->allocateBufferWithBackup(
                        mNode, portIndex, mem, &buffer);
            }
        } else if (portIndex == kPortIndexOutput
                && (mQuirks & kRequiresAllocateBufferOnOutputPorts)) {
            if (mOMXLivesLocally) {
                mem.clear();

                err = mOMX->allocateBuffer(
                        mNode, portIndex, def.nBufferSize, &buffer,
                        &info.mData);
            } else {
                err = mOMX->allocateBufferWithBackup(
                        mNode, portIndex, mem, &buffer);
            }
        } else {
            err = mOMX->useBuffer(mNode, portIndex, mem, &buffer);
        }

        if (err != OK) {
            ALOGE("allocate_buffer_with_backup failed");
            return err;
        }

        if (mem != NULL) {
            info.mData = mem->pointer();
        }

        info.mBuffer = buffer;
        info.mStatus = OWNED_BY_US;
        info.mMem = mem;
        info.mMediaBuffer = NULL;

        if (portIndex == kPortIndexOutput) {
            if (!(mOMXLivesLocally
                        && (mQuirks & kRequiresAllocateBufferOnOutputPorts)
                        && (mQuirks & kDefersOutputBufferAllocation))) {
                // If the node does not fill in the buffer ptr at this time,
                // we will defer creating the MediaBuffer until receiving
                // the first FILL_BUFFER_DONE notification instead.
                info.mMediaBuffer = new MediaBuffer(info.mData, info.mSize);
                info.mMediaBuffer->setObserver(this);
            }
        }

        mPortBuffers[portIndex].push(info);

        CODEC_LOGV("allocated buffer %p on %s port", buffer,
             portIndex == kPortIndexInput ? "input" : "output");
    }

    if (portIndex == kPortIndexOutput) {

        sp<MetaData> meta = mSource->getFormat();
        int32_t delay = 0;
        if (!meta->findInt32(kKeyEncoderDelay, &delay)) {
            delay = 0;
        }
        int32_t padding = 0;
        if (!meta->findInt32(kKeyEncoderPadding, &padding)) {
            padding = 0;
        }
        int32_t numchannels = 0;
        if (delay + padding) {
            if (mOutputFormat->findInt32(kKeyChannelCount, &numchannels)) {
                size_t frameSize = numchannels * sizeof(int16_t);
                if (mSkipCutBuffer != NULL) {
                    size_t prevbuffersize = mSkipCutBuffer->size();
                    if (prevbuffersize != 0) {
                        ALOGW("Replacing SkipCutBuffer holding %d bytes", prevbuffersize);
                    }
                }
                mSkipCutBuffer = new SkipCutBuffer(delay * frameSize, padding * frameSize);
            }
        }
    }

    // dumpPortStatus(portIndex);

    if (portIndex == kPortIndexInput && (mFlags & kUseSecureInputBuffers)) {
        Vector<MediaBuffer *> buffers;
        for (size_t i = 0; i < def.nBufferCountActual; ++i) {
            const BufferInfo &info = mPortBuffers[kPortIndexInput].itemAt(i);

            MediaBuffer *mbuf = new MediaBuffer(info.mData, info.mSize);
            buffers.push(mbuf);
        }

        status_t err = mSource->setBuffers(buffers);

        if (err != OK) {
            for (size_t i = 0; i < def.nBufferCountActual; ++i) {
                buffers.editItemAt(i)->release();
            }
            buffers.clear();

            CODEC_LOGE(
                    "Codec requested to use secure input buffers but "
                    "upstream source didn't support that.");

            return err;
        }
    }

    return OK;
}

    这个数函挺主要的，omx node是通过port来通信的，inport和output，入输node只有inport，而输出node就只有outport，间中码解的node就要需两个port

    先看inport的内存分配，有两个数函 allocatebuffer 和 usebuffer，如果不要需node重新分配内存，那就只要需用使application分配的内存，否则会在port面上重新分配内存

    为什么要需再port面上重新分配内存呢，多是DRM等原因虑考。

    在看一下outport的分配

{
    // Get the number of buffers needed.
    OMX_PARAM_PORTDEFINITIONTYPE def;
    InitOMXParams(&def);
    def.nPortIndex = kPortIndexOutput;

    status_t err = mOMX->getParameter(
            mNode, OMX_IndexParamPortDefinition, &def, sizeof(def));
    if (err != OK) {
        return err;
    }

    err = native_window_set_buffers_geometry(
            mNativeWindow.get(),
            def.format.video.nFrameWidth,
            def.format.video.nFrameHeight,
            def.format.video.eColorFormat);

    if (err != 0) {
        ALOGE("native_window_set_buffers_geometry failed: %s (%d)",
                strerror(-err), -err);
        return err;
    }
    initNativeWindowCrop();
    err = applyRotation();
    if (err != OK) {
        return err;
    }

    // Set up the native window.
    OMX_U32 usage = 0;
    err = mOMX->getGraphicBufferUsage(mNode, kPortIndexOutput, &usage);
    if (err != 0) {
        ALOGW("querying usage flags from OMX IL component failed: %d", err);
        // XXX: Currently this error is logged, but not fatal.
        usage = 0;
    }
    if (mFlags & kEnableGrallocUsageProtected) {
        usage |= GRALLOC_USAGE_PROTECTED;
    }

    // Make sure to check whether either Stagefright or the video decoder
    // requested protected buffers.
    if (usage & GRALLOC_USAGE_PROTECTED) {
        // Verify that the ANativeWindow sends images directly to
        // SurfaceFlinger.
        int queuesToNativeWindow = 0;
        err = mNativeWindow->query(
                mNativeWindow.get(), NATIVE_WINDOW_QUEUES_TO_WINDOW_COMPOSER,
                &queuesToNativeWindow);
        if (err != 0) {
            ALOGE("error authenticating native window: %d", err);
            return err;
        }
        if (queuesToNativeWindow != 1) {
            ALOGE("native window could not be authenticated");
            return PERMISSION_DENIED;
        }
    }

    ALOGV("native_window_set_usage usage=0x%lx", usage);

    /* all commons */
    usage |= (GRALLOC_USAGE_HW_TEXTURE | GRALLOC_USAGE_EXTERNAL_DISP);

    ALOGV("native_window_set_usage usage=0x%lx", usage);
    err = native_window_set_usage(
            mNativeWindow.get(), usage | GRALLOC_USAGE_HW_TEXTURE | GRALLOC_USAGE_EXTERNAL_DISP);
    if (err != 0) {
        ALOGE("native_window_set_usage failed: %s (%d)", strerror(-err), -err);
        return err;
    }
    int minUndequeuedBufs = 0;
    err = mNativeWindow->query(mNativeWindow.get(),
            NATIVE_WINDOW_MIN_UNDEQUEUED_BUFFERS, &minUndequeuedBufs);
    if (err != 0) {
        ALOGE("NATIVE_WINDOW_MIN_UNDEQUEUED_BUFFERS query failed: %s (%d)",
                strerror(-err), -err);
        return err;
    }

    // XXX: Is this the right logic to use?  It's not clear to me what the OMX
    // buffer counts refer to - how do they account for the renderer holding on
    // to buffers?
    if (def.nBufferCountActual < def.nBufferCountMin + minUndequeuedBufs) {
        OMX_U32 newBufferCount = def.nBufferCountMin + minUndequeuedBufs;
        def.nBufferCountActual = newBufferCount;
        err = mOMX->setParameter(
                mNode, OMX_IndexParamPortDefinition, &def, sizeof(def));
        if (err != OK) {
            CODEC_LOGE("setting nBufferCountActual to %lu failed: %d",
                    newBufferCount, err);
            return err;
        }
    }

    err = native_window_set_buffer_count(
            mNativeWindow.get(), def.nBufferCountActual);
    if (err != 0) {
        ALOGE("native_window_set_buffer_count failed: %s (%d)", strerror(-err),
                -err);
        return err;
    }

    CODEC_LOGV("allocating %lu buffers from a native window of size %lu on "
            "output port", def.nBufferCountActual, def.nBufferSize);

    // Dequeue buffers and send them to OMX
    for (OMX_U32 i = 0; i < def.nBufferCountActual; i++) {
        ANativeWindowBuffer* buf;
        err = mNativeWindow->dequeueBuffer(mNativeWindow.get(), &buf);
        if (err != 0) {
            ALOGE("dequeueBuffer failed: %s (%d)", strerror(-err), -err);
            break;
        }

        sp<GraphicBuffer> graphicBuffer(new GraphicBuffer(buf, false));
        BufferInfo info;
        info.mData = NULL;
        info.mSize = def.nBufferSize;
        info.mStatus = OWNED_BY_US;
        info.mMem = NULL;
        info.mMediaBuffer = new MediaBuffer(graphicBuffer);
        info.mMediaBuffer->setObserver(this);
        mPortBuffers[kPortIndexOutput].push(info);

        IOMX::buffer_id bufferId;
        err = mOMX->useGraphicBuffer(mNode, kPortIndexOutput, graphicBuffer,
                &bufferId);
        if (err != 0) {
            CODEC_LOGE("registering GraphicBuffer with OMX IL component "
                    "failed: %d", err);
            break;
        }

        mPortBuffers[kPortIndexOutput].editItemAt(i).mBuffer = bufferId;

        CODEC_LOGV("registered graphic buffer with ID %p (pointer = %p)",
                bufferId, graphicBuffer.get());
    }

    OMX_U32 cancelStart;
    OMX_U32 cancelEnd;
    if (err != 0) {
        // If an error occurred while dequeuing we need to cancel any buffers
        // that were dequeued.
        cancelStart = 0;
        cancelEnd = mPortBuffers[kPortIndexOutput].size();
    } else {
        // Return the last two buffers to the native window.
        cancelStart = def.nBufferCountActual - minUndequeuedBufs;
        cancelEnd = def.nBufferCountActual;
    }

    for (OMX_U32 i = cancelStart; i < cancelEnd; i++) {
        BufferInfo *info = &mPortBuffers[kPortIndexOutput].editItemAt(i);
        cancelBufferToNativeWindow(info);
    }

    return err;
}

    start的预备也做完了，主要是给port分配内存，基本也只是摘抄代码了

    start当前，就要kick off了，下篇开始播放了

    

    

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