CUDA GstBuffer output buffer with OpenCV GpuMat

[Richard Pickler]

Thanks for the speedy reply.  I've replaced the standard buffer_map with
the following


    GstVideoFrame out_frame;
    if (!gst_video_frame_map (&out_frame, &debayer->info, outbuf,
                (GstMapFlags)(GST_MAP_WRITE | GST_MAP_CUDA))) {
        //gst_video_frame_unmap (&in_frame);
        GST_ERROR_OBJECT (debayer, "Failed to map output buffer");
        std::cout << "Failed to map output buffer" << std::endl;
        return GST_FLOW_ERROR;
    }

And the gpuMat initialization:

    cv::cuda::GpuMat gpu_out(
        cv::Size(
            GST_VIDEO_FRAME_WIDTH(&out_frame),
            GST_VIDEO_FRAME_HEIGHT(&out_frame)),
        CV_8UC3,
        (char*) out_frame.data,
        GST_VIDEO_FRAME_PLANE_STRIDE(&out_frame, 0));

But no such luck.  Now I am the proud recipient of black frames.

You're correct that the stride is different.  5760 vs 6144 on my 1920 wide
image.  That seems to cause the demosaic function to overrun and cause a
memory exception in cuda.  I then changed the gpumat initialization to:


    cv::cuda::GpuMat gpu_out(
        cv::Size(
            out_frame.map[0].size / GST_VIDEO_FRAME_HEIGHT(&out_frame) / 3,
            GST_VIDEO_FRAME_HEIGHT(&out_frame)),
        CV_8UC3,
        (char*) out_frame.data,
        GST_VIDEO_FRAME_PLANE_STRIDE(&out_frame, 0));

Which doesn't crash, but also doesn't produce an image.

(sorry for duplicate.  I forgot to reply-all)

On Thu, Jun 8, 2023 at 2:22 PM Seungha Yang <seungha at centricular.com> wrote:

> Hi,
>
>
>
> GstCudaMemory’s stride is likely different from default one.
>
> You will need to use gst_video_frame_map() and
> GST_VIDEO_FRAME_PLANE_STRIDE(frame, 0), or GstCudaMemory.info.stride[0]
>
>
>
> Regards,
>
> Seungha
>
>
>
> *From:* gstreamer-devel <gstreamer-devel-bounces at lists.freedesktop.org> *On
> Behalf Of *Richard Pickler via gstreamer-devel
> *Sent:* Thursday, June 8, 2023 10:05 PM
> *To:* gstreamer-devel at lists.freedesktop.org
> *Cc:* Richard Pickler <rpickler at gmail.com>
> *Subject:* CUDA GstBuffer output buffer with OpenCV GpuMat
>
>
>
> I'm struggling to use the recent cuda improvements in gstreamer, using an
> OpenCV GpuMat to write to a CUDAMemory outbuf.  I'm was successful in
> getting an appropriate buffer through decide/propose_allocation, but simply
> cannot seem to write to a buffer properly.  In my transform function below,
> I'm able to map the buffer and have the demosaic function run properly, but
> the output stream comes out garbage.  I placed a simple cv::imwrite in the
> code, and sure enough, the data comes through the function properly, it's
> just not in a structure that gstreamer is happy with.
>
>
>
> Any ideas?  I've been pounding my head against this wall for a couple days
> now.
>
>
>
> static GstFlowReturn
> debayer_transform(GstBaseTransform *base,
>                   GstBuffer *inbuf, GstBuffer *outbuf)
> {
>     Debayer *debayer = DEBAYER(base);
>     GstCudaBaseTransform *btrans = GST_CUDA_BASE_TRANSFORM (base);
>
>     if (gst_buffer_n_memory (outbuf) != 1) {
>         GST_ERROR_OBJECT (debayer, "Invalid output buffer");
>         return GST_FLOW_ERROR;
>     }
>
>     GstMemory *mem;
>     mem = gst_buffer_peek_memory (outbuf, 0);
>     if (!gst_is_cuda_memory (mem)) {
>         GST_ERROR_OBJECT (debayer, "Input buffer is not CUDA");
>         std::cout << "Input buffer is not cuda" << std::endl;
>         return GST_FLOW_ERROR;
>     }
>
>     GstMapInfo map;
>     if(!gst_buffer_map(inbuf, &map, GST_MAP_READ))
>     {
>         std::cout << "Can't map" << std::endl;
>         return GST_FLOW_ERROR;
>     }
>
>     GstMapInfo outmap;
>     if(!gst_buffer_map(outbuf, &outmap, (GstMapFlags)(GST_MAP_WRITE |
> GST_MAP_CUDA)))
>     {
>         std::cout << "Can't map" << std::endl;
>         return GST_FLOW_ERROR;
>     }
>
>     cv::Mat in(
>         cv::Size(debayer->info.width, debayer->info.height), CV_8UC1,
>         (char*) map.data);
>
>     cv::cuda::GpuMat gpu_in;
>
>     cv::cuda::GpuMat gpu_out(
>         cv::Size(debayer->info.width, debayer->info.height),
>         CV_8UC3,
>         (char*) outmap.data, debayer->info.stride[0]);
>
>     gpu_in.upload(in);
>     cv::cuda::demosaicing(gpu_in, gpu_out, cv::COLOR_BayerRG2BGR);
>     cv::Mat out(gpu_out);
>     cv::imwrite("foo.jpg", out);
>
>     gst_buffer_unmap(inbuf, &map);
>     gst_buffer_unmap(outbuf, &outmap);
>     return GST_FLOW_OK;
> }
>
>
>
>
>
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