AJA Source Operator

Authors: Holoscan Team (NVIDIA)
Supported platforms: x86_64, aarch64
Language: C++, Python
Last modified: August 5, 2025
Latest version: 1.0
Minimum Holoscan SDK version: 1.0.3
Tested Holoscan SDK versions: 2.0.0
Contribution metric: Level 1 - Highly Reliable

The AJA Source operator provides functionality to capture high-quality video streams from AJA capture cards and devices. It offers comprehensive support for both SDI (Serial Digital Interface) and HDMI (High-Definition Multimedia Interface) input sources, allowing for professional video capture in various formats and resolutions. The operator is designed to work seamlessly with AJA's hardware capabilities, including features like frame synchronization and format detection. Additionally, it provides an optional overlay channel capability that enables real-time mixing and compositing of multiple video streams, making it suitable for applications requiring picture-in-picture, graphics overlay, or other video mixing scenarios.

Requirements

• AJA capture card (e.g., KONA HDMI)
• CUDA-capable GPU
• Holoscan SDK 1.0.3 or later

Parameters

The following parameters can be configured for this operator:

Parameter	Type	Description	Default
device	string	Device specifier (e.g., "0" for device 0)	"0"
channel	NTV2Channel	Camera channel to use for input	NTV2_CHANNEL1
width	uint32_t	Width of the video stream	1920
height	uint32_t	Height of the video stream	1080
framerate	uint32_t	Frame rate of the video stream	60
interlaced	bool	Whether the video is interlaced	false
rdma	bool	Enable RDMA for video input	false
enable_overlay	bool	Enable overlay channel	false
overlay_channel	NTV2Channel	Camera channel to use for overlay	NTV2_CHANNEL2
overlay_rdma	bool	Enable RDMA for overlay	false

Supported Video Formats

The operator supports various video formats based on resolution, frame rate, and scan type:

• 720p (1280x720) at 50/59.94/60 fps
• 1080i (1920x1080) at 50/59.94/60 fps
• 1080p (1920x1080) at 23.98/24/25/29.97/30/50/59.94/60 fps
• UHD (3840x2160) at 23.98/24/25/29.97/30/50/59.94/60 fps
• 4K (4096x2160) at 23.98/24/25/29.97/30/50/59.94/60 fps

Input Ports

• overlay_buffer_input (optional): Video buffer for overlay mixing when enable_overlay is true

Output Ports

• video_buffer_output: Video buffer containing the captured frame
• overlay_buffer_output (optional): Empty video buffer for overlay when enable_overlay is true

API Reference

Python

AJASourceOp

Operator to get a video stream from an AJA capture card.

==Named Inputs==

overlay_buffer_input : nvidia::gxf::VideoBuffer (optional)
    The operator does not require a message on this input port in order for ``compute`` to be
    called. If a message is found, and ``enable_overlay`` is ``True``, the image will be mixed
    with the image captured by the AJA card. If ``enable_overlay`` is ``False``, any message on
    this port will be ignored.

==Named Outputs==

video_buffer_output : nvidia::gxf::VideoBuffer
    The output video frame from the AJA capture card. If ``overlay_rdma`` is ``True``, this
    video buffer will be on the device, otherwise it will be in pinned host memory.
overlay_buffer_output : nvidia::gxf::VideoBuffer (optional)
    This output port will only emit a video buffer when ``enable_overlay`` is ``True``. If
    ``overlay_rdma`` is ``True``, this video buffer will be on the device, otherwise it will be
    in pinned host memory.

Parameters

fragment : holoscan.core.Fragment (constructor only) The fragment that the operator belongs to. device : str, optional The device to target (e.g., "0" for device 0). Default value is "0". channel : holoscan.operators.NTV2Channel or int, optional The camera NTV2Channel to use for output (e.g., NTV2Channel.NTV2_CHANNEL1 (0) or "NTV2_CHANNEL1" (in YAML) for the first channel). Default value is NTV2Channel.NTV2_CHANNEL1 ("NTV2_CHANNEL1" in YAML). width : int, optional Width of the video stream. Default value is 1920. height : int, optional Height of the video stream. Default value is 1080. framerate : int, optional Frame rate of the video stream. Default value is 60. interlaced : bool, optional Whether or not the video is an interlaced format. Default value is False ("false" in YAML). rdma : bool, optional Boolean indicating whether RDMA is enabled. Default value is False ("false" in YAML). enable_overlay : bool, optional Boolean indicating whether a separate overlay channel is enabled. Default value is False ("false" in YAML). overlay_channel : holoscan.operators.NTV2Channel or int, optional The camera NTV2Channel to use for overlay output. Default value is NTV2Channel.NTV2_CHANNEL2 ("NTV2_CHANNEL2" in YAML). overlay_rdma : bool, optional Boolean indicating whether RDMA is enabled for the overlay. Default value is False ("false" in YAML). name : str, optional (constructor only) The name of the operator. Default value is "aja_source".