What Is an LED Sending Card? Complete Guide to Functions, Types & Buying | ColorlightIntroduction
Every LED display — whether it's a retail advertising screen, a concert stage, a sports stadium, or a virtual production studio — relies on a sophisticated control system to transform video into millions of synchronized LED pixels.
At the heart of this system is the LED sending card. Acting as the bridge between your video source and the display itself, it processes incoming video signals, maps them to the screen layout, and distributes synchronized data to every receiving card across the LED wall.
Without a sending card, even the most advanced LED display cannot reproduce images accurately or reliably. In this guide, you'll learn what an LED sending card is, how it works, how it differs from receiving cards and video processors, and how to choose the right solution for your project.
What Is an LED Sending Card?
An LED sending card (also called a sender, sending box, or LED controller) is a hardware device that converts video signals from a source — a computer, media server, camera, or player — into a format that LED display systems can transmit and display. LED sending cards are available as built-in PCIe cards or integrated inside external sending boxes and video processors.
Think of it as the translator and dispatcher in your LED system: it receives video data, processes it, packages it, and sends it over Ethernet or fiber to the receiving cards inside each LED cabinet. The name describes its primary role — it sends data, while the receiving cards receive and decode it.
Why Every LED Display Needs a Sending Card
You might wonder: why can't I just plug an HDMI cable directly into an LED screen?
Here's why:
| Problem | Why a Sending Card Is Required |
|---|
| Non-standard resolutions | LED walls are modular — a screen might be 2,560×1,440. Sending cards map video to the exact pixel grid. |
| Signal format mismatch | HDMI transmits standard digital video signals, while LED receiving cards require dedicated control data generated by the sending card. |
| Data distribution | Dozens or hundreds of receiving cards need synchronized data — the sending card distributes it. |
| Image control | Without a sending card, you lose brightness, color temperature, grayscale, and refresh rate control. |
Signal Flow Diagram
How Does an LED Sending Card Work?
| Step | Function |
|---|
| 1. Receive | Accepts video input via HDMI, DVI, SDI, or DP |
| 2. Process | Decodes and adjusts resolution, color space, and bit depth |
| 3. Pixel Mapping | Maps every pixel in the input image to its exact physical location on the LED display, ensuring correct cabinet and module alignment. |
| 4. Encode | Packages pixel data into Ethernet protocol |
| 5. Transmit | Sends data to all receiving cards |
| 6. Decode | Each receiving card extracts its portion |
| 7. Display | LED modules show the final image |
LED Display Signal Flow Explained
What Does an LED Sending Card Actually Do?
| Function | Description |
|---|
| Video Signal Reception | Accepts input from HDMI, DVI, SDI, or DP sources |
| Video Processing | Color space conversion, bit depth scaling, signal conversion, and output configuration. |
| Pixel Mapping | LED displays rarely use standard resolutions such as 1920×1080. Instead, they are built from modular cabinets with custom pixel dimensions. The sending card calculates exactly which pixels belong to each receiving card, ensuring seamless image reproduction. |
| Data Encoding | Packages pixel data for transmission to receiving cards |
| Signal Distribution | Sends data to multiple receiving cards via Ethernet outputs |
| Synchronization | Ensures all cabinets display the same frame simultaneously |
| Display Management | Adjusts brightness, contrast, color temperature, and presets |
| Device Communication | Communicates with control software for real-time adjustments |
Sending Card vs Receiving Card
| Aspect | Sending Card | Receiving Card |
|---|
| Location | In PC, processor, or sending box | Inside each LED cabinet |
| Role | Sends data | Receives and executes data |
| Function | Encodes, maps, distributes | Decodes and drives pixels |
| Quantity | 1–2 per system | One per cabinet |
| Key Action | Transmits | Displays |
Sending Card vs Video Processor
| Aspect | Sending Card | Video Processor |
|---|
| Role | Transmits data to receiving cards | Processes and enhances video signals |
| Key Functions | Pixel mapping, data encoding, distribution | Scaling, color correction, HDR, multi-source switching |
| When Needed | Every LED system needs one | Only for complex installations |
| Built-in | Can be built into video processors | Often includes internal sending capability |
Many high-end video processors have built-in sending cards — eliminating the need for a separate sending box. This reduces cabling and simplifies installation.
Types of LED Sending Devices
Today, most professional LED control systems fall into one of three architectures.
1. Built-in Sending Cards (Internal)
- What: PCIe circuit board installed inside a computer chassis
- Advantages: Space-efficient, cost-effective
- Disadvantages: Not portable, requires a dedicated PC
- Best for: Fixed installations, broadcast studios, command centers
2. External Sending Boxes
- What: Self-contained unit with its own enclosure and power supply
- Advantages: Portable, rugged, plug-and-play
- Disadvantages: Higher cost, requires rack space
- Best for: Rental, staging, live events, outdoor installations
3. Video Processors with Integrated Sending
- What: Professional video processor with built-in sending capability
- Advantages: Simplified system design, reduced cabling
- Disadvantages: Higher initial cost
- Best for: Broadcast, XR, high-end rental and staging
Key Specifications to Consider
| Specification | What to Look For |
|---|
| Loading Capacity | Total pixels the device can drive — match to your screen resolution |
| Input Resolution | Maximum input the device can accept — 4K or 8K ready |
| Video Interfaces | HDMI, DVI, SDI, DP, USB-C — match your sources |
| Ethernet Outputs | More ports = more cabinets supported |
| Fiber Transmission | Required for distances over 100 meters |
| Synchronization | Genlock for broadcast and virtual production |
| Redundancy | Dual power inputs, backup cards for mission-critical systems |
| Compatibility | Ensure compatibility with your receiving cards and control software |
Colorlight Sending Solutions
Built-in Sending Cards
For fixed installations where the control system is housed in a dedicated PC or video processor. Space-efficient and cost-effective.
Best for: Fixed installations, broadcast studios, command centers.
S Series Sending Boxes
| Model | Best For |
|---|
| S2 | Small & medium commercial displays |
| S4 | Medium-sized installations |
| S6 | Rental, staging, events |
| S20F | Large-scale displays, broadcast, professional applications |
Video Processors with Built-in Sending
For projects requiring both video processing and sending capability — professional-grade scaling, HDR, multi-source switching, and integrated sending in one device.
Best for: Broadcast studios, XR virtual production, high-end rental and staging.
How to Choose the Right Sending Solution
| Step | Consideration |
|---|
| 1. Identify your input source | Single PC → basic card. Multiple sources → processor |
| 2. Calculate screen resolution | Width × Height = total pixels — determines loading capacity |
| 3. Need scaling? | No → sending card. Yes → video processor |
| 4. Installation environment | Fixed indoor → built-in. Rental/outdoor → sending box |
| 5. Transmission distance | Under 100m → Ethernet. Over 100m → fiber |
| 6. Choose your model | Match capacity, environment, and budget |
Typical Applications
| Application | Recommended Solution |
|---|
| Commercial Signage | Built-in card or S2/S4 |
| Rental & Staging | S6 or S20F |
| Broadcast Studios | Built-in card or integrated processor |
| XR Virtual Production | Integrated video processor |
| Sports Venues | S20F or integrated processor |
| Transportation Hubs | Sending box with fiber |
| Command Centers | Built-in card or integrated processor |
Frequently Asked Questions
| Question | Answer |
|---|
| What is an LED sending card? | A device that converts video signals into a format LED receiving cards can use. |
| Does every LED display need one? | Yes — every LED system requires a sending card or integrated processor. |
| Sending card vs receiving card? | Sending card sends data; receiving card receives and drives pixels. |
| Sending card vs video processor? | Sending card transmits; video processor scales and enhances. Many processors include sending. |
| Can one sending card control multiple cabinets? | Yes — through multiple Ethernet outputs, up to the card's loading capacity. |
| Can I use HDMI without a sending card? | No — HDMI must be converted to the receiving card protocol. |
| What is a sending box? | A standalone, rugged external sending device. |
| How do I choose the right sending card? | Consider resolution, sources, environment, distance, and whether you need scaling. |
| Do sending cards support 4K/8K? | Yes — if the device has sufficient input bandwidth and loading capacity. |
| Are Colorlight sending cards compatible with all receiving cards? | Fully compatible with Colorlight receiving cards; K Series and 5G Series offer broad third-party compatibility. |
Summary
| Product | Type | Best For |
|---|
| Built-in Sending Card | Internal PCIe | Fixed installations, cost-effective |
| S2 | External Sending Box | Small & medium commercial displays |
| S4 | External Sending Box | Medium-sized installations |
| S6 | External Sending Box | Rental, staging, events |
| S20F | External Sending Box | Large-scale, broadcast, professional |
| X and Xm Series Processors | Integrated Processor + Sending | Broadcast, XR, high-end rental |
The sending card is the essential first link in the LED control chain. Choose the right solution based on your screen size, application, environment, and future requirements.
Whether you're building a digital signage network, a fine-pitch control room, a concert stage, or a virtual production studio, selecting the right LED sending solution is the foundation of a stable and high-performance display system.
Colorlight offers a complete portfolio of built-in sending cards, external sending boxes, and integrated video processors to help professionals build reliable LED display systems of every scale.
Further Reading
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