void CpuConsumer::freeBufferLocked(int slotIndex) {
    if (mBufferPointers[slotIndex] != NULL) {
        status_t err;
        CC_LOGW("Buffer %d freed while locked by consumer", slotIndex);
        mBufferPointers[slotIndex] = NULL;
        err = mSlots[slotIndex].mGraphicBuffer->unlock();
        if (err != OK) {
            CC_LOGE("%s: Unable to unlock graphic buffer %d", __FUNCTION__,
                    slotIndex);
        }
        mCurrentLockedBuffers--;
    }
    ConsumerBase::freeBufferLocked(slotIndex);
}
status_t CpuConsumer::lockNextBuffer(LockedBuffer *nativeBuffer) {
    status_t err;

    if (!nativeBuffer) return BAD_VALUE;
    if (mCurrentLockedBuffers == mMaxLockedBuffers) {
        CC_LOGW("Max buffers have been locked (%zd), cannot lock anymore.",
                mMaxLockedBuffers);
        return NOT_ENOUGH_DATA;
    }

    BufferItem b;

    Mutex::Autolock _l(mMutex);

    err = acquireBufferLocked(&b, 0);
    if (err != OK) {
        if (err == BufferQueue::NO_BUFFER_AVAILABLE) {
            return BAD_VALUE;
        } else {
            CC_LOGE("Error acquiring buffer: %s (%d)", strerror(err), err);
            return err;
        }
    }

    int slot = b.mSlot;

    void *bufferPointer = NULL;
    android_ycbcr ycbcr = android_ycbcr();

    PixelFormat format = mSlots[slot].mGraphicBuffer->getPixelFormat();
    PixelFormat flexFormat = format;
    if (isPossiblyYUV(format)) {
        if (b.mFence.get()) {
            err = mSlots[slot].mGraphicBuffer->lockAsyncYCbCr(
                GraphicBuffer::USAGE_SW_READ_OFTEN,
                b.mCrop,
                &ycbcr,
                b.mFence->dup());
        } else {
            err = mSlots[slot].mGraphicBuffer->lockYCbCr(
                GraphicBuffer::USAGE_SW_READ_OFTEN,
                b.mCrop,
                &ycbcr);
        }
        if (err == OK) {
            bufferPointer = ycbcr.y;
            flexFormat = HAL_PIXEL_FORMAT_YCbCr_420_888;
            if (format != HAL_PIXEL_FORMAT_YCbCr_420_888) {
                CC_LOGV("locking buffer of format %#x as flex YUV", format);
            }
        } else if (format == HAL_PIXEL_FORMAT_YCbCr_420_888) {
            CC_LOGE("Unable to lock YCbCr buffer for CPU reading: %s (%d)",
                    strerror(-err), err);
            return err;
        }
    }

    if (bufferPointer == NULL) { // not flexible YUV
        if (b.mFence.get()) {
            err = mSlots[slot].mGraphicBuffer->lockAsync(
                GraphicBuffer::USAGE_SW_READ_OFTEN,
                b.mCrop,
                &bufferPointer,
                b.mFence->dup());
        } else {
            err = mSlots[slot].mGraphicBuffer->lock(
                GraphicBuffer::USAGE_SW_READ_OFTEN,
                b.mCrop,
                &bufferPointer);
        }
        if (err != OK) {
            CC_LOGE("Unable to lock buffer for CPU reading: %s (%d)",
                    strerror(-err), err);
            return err;
        }
    }

    size_t lockedIdx = 0;
    for (; lockedIdx < static_cast<size_t>(mMaxLockedBuffers); lockedIdx++) {
        if (mAcquiredBuffers[lockedIdx].mSlot ==
                BufferQueue::INVALID_BUFFER_SLOT) {
            break;
        }
    }
    assert(lockedIdx < mMaxLockedBuffers);

    AcquiredBuffer &ab = mAcquiredBuffers.editItemAt(lockedIdx);
    ab.mSlot = slot;
    ab.mBufferPointer = bufferPointer;
    ab.mGraphicBuffer = mSlots[slot].mGraphicBuffer;

    nativeBuffer->data   =
            reinterpret_cast<uint8_t*>(bufferPointer);
    nativeBuffer->width  = mSlots[slot].mGraphicBuffer->getWidth();
    nativeBuffer->height = mSlots[slot].mGraphicBuffer->getHeight();
    nativeBuffer->format = format;
    nativeBuffer->flexFormat = flexFormat;
    nativeBuffer->stride = (ycbcr.y != NULL) ?
            static_cast<uint32_t>(ycbcr.ystride) :
            mSlots[slot].mGraphicBuffer->getStride();

    nativeBuffer->crop        = b.mCrop;
    nativeBuffer->transform   = b.mTransform;
    nativeBuffer->scalingMode = b.mScalingMode;
    nativeBuffer->timestamp   = b.mTimestamp;
    nativeBuffer->dataSpace   = b.mDataSpace;
    nativeBuffer->frameNumber = b.mFrameNumber;

    nativeBuffer->dataCb       = reinterpret_cast<uint8_t*>(ycbcr.cb);
    nativeBuffer->dataCr       = reinterpret_cast<uint8_t*>(ycbcr.cr);
    nativeBuffer->chromaStride = static_cast<uint32_t>(ycbcr.cstride);
    nativeBuffer->chromaStep   = static_cast<uint32_t>(ycbcr.chroma_step);

    mCurrentLockedBuffers++;

    return OK;
}