NvBufferMemMap() Pointer clean up

[nikolay.soserov]

Hello,

I was wondering if the pointer I get back from the NvBufferMemMap() can be freed just using free() or do I need some special clean up for it ?

[DaneLLL]

Hi,
Please call this API to unmap the memory:

/**
* Unmaps the mapped virtual address of the plane.
*
* If the following conditions are both true, the client must call
* NvBufferMemSyncForDevice() before unmapping the memory:
* - Mapped memory was modified by the CPU.
* - Mapped memory will be accessed by a hardware device.
*
* @param[in] dmabuf_fd  DMABUF FD of the buffer.
* @param[in] plane      Video frame plane. Applies to
*                       @ref NvBufferPayload_SurfArray.
* @param[in] pVirtAddr  Virtual address pointer to the memory-mapped plane.
*
* @returns 0 for success, -1 for failure.
*/
int NvBufferMemUnMap (int dmabuf_fd, unsigned int plane, void **pVirtAddr);

[nikolay.soserov]

@DaneLLL

* If the following conditions are both true, the client must call

I currently have the following code to decode an image into a cv::Mat

cv::Mat JpegDecoder::DecodeToCvMat(std::string file_path, cv::ColorConversionCodes conv_code) {
    int fd = 0;
    int nvbuffer = 0;
    uint32_t width, height, pixfmt;
    void *pdata = NULL;

    std::ifstream in_file = std::ifstream(file_path);
    uint64_t in_file_size = get_file_size(&in_file);
    unsigned char in_buffer[in_file_size];

    in_file.read((char *) in_buffer, in_file_size);

    jpegdec->decodeToFd(fd, in_buffer, in_file_size, pixfmt,
        width, height);

    NvBufferCreateParams params;
    params.width = width;
    params.height = height;
    params.layout = NvBufferLayout_Pitch;
    params.colorFormat = NvBufferColorFormat_ABGR32;
    params.nvbuf_tag = NvBufferTag::NvBufferTag_JPEG;
    params.payloadType = NvBufferPayloadType::NvBufferPayload_SurfArray;

    NvBufferCreateEx(&nvbuffer, &params);

    NvBufferTransform(fd, nvbuffer, &transform_params);

    NvBufferMemMap(nvbuffer, 0, NvBufferMem_Read_Write, &pdata);

    NvBufferMemSyncForCpu(nvbuffer, 0, &pdata);

    cv::Mat nv_buf_mat = cv::Mat(height, width, CV_8UC4, pdata);

    cv::Mat output_mat;
    cv::cvtColor(nv_buf_mat, output_mat, conv_code);

    NvBufferMemUnMap(nvbuffer, 0, &pdata);

    in_file.close();
    return output_mat;
}```

But there is a memory leak somewhere because if I call it in a loop just decoding images into cv::Mat() which gets destroyed immediately after making it I run out of memory.  
That is why I am asking if there are any extra steps I need to take in order to free the memory besides the call to NvBufferMemUnMap or maybe there is something else wrong with my code for decoding.

[DaneLLL]

Hi,
We only see NvBufferCreateEx() in the code. Please make sure you also call NvBufferDestroy() in pair. Or call NvBufferCreateEx() once and reuse the NvBuffer.