Modifying timestamp in NitrosImage without GPU copy

[HiddenNetwork]

Hi there,

I would like to modify the timestamp on an existing NitrosImage (or NitrosImageView) but am running into cuda issues.

I have two independent ArgusMonoNode’s running, and am trying to use the nitros::message_filters to synchronize (via message_filters::Synchronizer<ApproxSyncPolicy>) the two images (and their CameraInfos). Following the NitrosCameraDropNode example, I was able to get a callback with all topics triggered, but I am not sure how I can re-timestamp the NitrosImages without copying the underlying data.

In the callback, if I wrap the incoming NitrosImage::ConstSharedPtr with a NitrosImageView, then create a new NitrosImage with NitrosImageBuilder (accessing data with .GetGpuData()), I get the following error:

2025-08-25 10:30:03.552 ERROR gxf/std/unbounded_allocator.cpp@99: Failure in cudaFree. cuda_error: cudaErrorInvalidValue, error_str: invalid argument

This method seems problematic, likely some issue with memory ownership.

How else can I modify the timestamp of the incoming NitrosImage, without copying the underlying GPU data?

Is it possible to add a NitrosImageView.SetTimestampSeconds() & NitrosImageView.SetTimestampNanoseconds() functionality?

Longer code snippet:

void sync_callback(const nvidia::isaac_ros::nitros::NitrosImage::ConstSharedPtr &left_img_ptr,
                    const sensor_msgs::msg::CameraInfo::ConstSharedPtr &left_cam_info_ptr,
                    const nvidia::isaac_ros::nitros::NitrosImage::ConstSharedPtr &right_img_ptr,
                    const sensor_msgs::msg::CameraInfo::ConstSharedPtr &right_cam_info_ptr) {

    auto left_image_view  = nvidia::isaac_ros::nitros::NitrosImageView(*left_img_ptr);
    auto right_image_view = nvidia::isaac_ros::nitros::NitrosImageView(*right_img_ptr);

    // Get "now" timestamp
    rclcpp::Time now = this->now();

    // Left header data
    std_msgs::msg::Header left_header;
    left_header.stamp    = now;
    left_header.frame_id = left_image_view.GetFrameId();  // todo update

    // TODO: Below causes a cudaFree error. How to resolve this??

    // Create NitrosImage wrapping CUDA buffer of left nitros image
    nvidia::isaac_ros::nitros::NitrosImage left_nitros_image =
        nvidia::isaac_ros::nitros::NitrosImageBuilder()
            .WithHeader(left_header)
            .WithEncoding(img_encodings::RGB8)
            .WithDimensions(left_image_view.GetHeight(), left_image_view.GetWidth())
            .WithGpuData(const_cast<void *>(static_cast<const void *>(left_image_view.GetGpuData())))
            .Build();
    // ... etc ...
    // Republish images and Camera Info with all matching timestamps
    left_img_syncd_pub_->publish(left_nitros_image);
    // ... etc ...
}

[vchuang]

Hello @HiddenNetwork,

Welcome to the Isaac ROS forum!

From the error you described and the code snippet you provided, it seems like when you use NitrosImageBuilder().WithGpuData(), the resulting NitrosImageobject assumes ownership of the raw pointer passed to it. When the NitrosImage object is destroyed during handing off, it will call a deleter, which defaults to cudaFree() on that pointer. Since the original NitrosImage from the callback still owns and manages that exact same pointer, you get a double-free or an invalid free operation.

You could try adding WithReleaseCallback() before Build() like this reference usage, or you could use isaac_ros_pynitros with pynitros_image_view to set your image header.