Android Camera预览过程数据流浅析

    mPreviewHeap = mGetMemoryCb((int)mV4L2Camera->getCameraFd(),
                                aligned_buffer_size,
                                kBufferCount,
                                0); 

    if (mPreviewWindow && mGrallocHal) {
        buffer_handle_t *buf_handle;
        int stride;
        if (0 != mPreviewWindow->dequeue_buffer(mPreviewWindow, &buf_handle, &stride)) {
            ALOGE("Could not dequeue gralloc buffer!\n");
            goto callbacks;
        }

        void *vaddr;
        if (!mGrallocHal->lock(mGrallocHal,
                               *buf_handle,
                               GRALLOC_USAGE_SW_WRITE_OFTEN,
                               0, 0, width, height, &vaddr)) {
            char *frame = ((char *)mPreviewHeap->data) + offset;

            // the code below assumes YUV, not RGB
            {
                int h;
                char *src = frame;
                char *ptr = (char *)vaddr;
                memcpy(ptr, src, frame_size);
                //YUY2toYV12(frame, vaddr, width, height);
            }
            mGrallocHal->unlock(mGrallocHal, *buf_handle);
        }
        else
            ALOGE("%s: could not obtain gralloc buffer", __func__);

        if (0 != mPreviewWindow->enqueue_buffer(mPreviewWindow, buf_handle)) {
            ALOGE("Could not enqueue gralloc buffer!\n");
            goto callbacks;
        }
    }

    ret = ioctl(win->fd, VIDIOC_REQBUFS, &reqbuf);

    *len = buf.length;
    *start = mmap(NULL, buf.length, PROT_READ | PROT_WRITE, MAP_SHARED,
            fd, buf.m.offset);

    for (unsigned int i = 0; i < cur_layer->visibleRegionScreen.numRects; i++) {
        uint8_t *cur_dst_addr = dst_addr;
        uint8_t *cur_src_addr = src_addr;

        for (int j = 0; j < h ; j++) {
            memcpy(cur_dst_addr, cur_src_addr, cpy_size);
            cur_dst_addr = &cur_dst_addr[cpy_size];
            cur_src_addr = &cur_src_addr[(cur_layer->displayFrame.right - cur_layer->displayFrame.left) * (prev_handle->uiBpp / 8)];
        }
        cur_rect++;
    }