Hardware vs. Software Graphics on Video Overlay Devices

Hardware Overlay

Software Overlay (Video I/O Devices)

On-board dedicated Hardware ICs do the Graphics and Video Mixing

Host PCs CPU and GPU do the Graphics and Video Mixing

No Video Frames sent back & forth across the PCI/PCIe Bus for graphics mixing and output

Video Frames must be sent back & forth across the PCI/PCIe Bus for graphics mixing and output

Low and fixed delays between incoming video and output video+graphics overlay regardless PC status

Long and in-deterministic delays between incoming video and output video+graphics overlay, depending on Host PC status

Low requirement on host PC's CPU, GPU, Graphics Card & PCIe Bus: 1XLane Gen 1 PCIe Slot OK for HD

High requirement on host PC's CPU, GPU, Graphics Card & PCIe Bus: Min. 2XLane PCIe Slot for HD

On-board overlay memory buffer available directly for application software to write/read overlay pixels

Continuous video frames sending to and receiving from host PC for any pixel overlay

Easy and instant overlay programming: just write 4-bytes ARGB for each video pixel overlay

Complicated and slow overlay process: even one pixel overlay requires successive full video frame data sent back and forth over the PCIe bus for host to mix

Support multiple overlay cards (even dozens) in one PC without degradation of host PC performance

Difficult to support multiple cards since each will consume significant CPU/GPU power to read/write continuous video frames

Using Separate Sockets to Simultaneously output Video with Overlay and Overlay Only (Key for external mixer) 

Cannot do so

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