LCD splicing screen system architecture: how to match the display layer, processing layer, control layer and signal layer

LCD splicing screen is not "buy a few screens to put together", but a system engineering composed of display layer, processing layer, control layer and signal layer. The signal is transmitted from bottom to top, and the control is sent from top to bottom: the signal layer is responsible for sending the signal, the processing layer is responsible for turning the signal into a picture that can be used by the splicing screen, the display layer is responsible for presenting the picture, and the control layer is responsible for directing the coordination of all layers. Whether the scheme can run stably for a long time depends on whether the four layers match, not whether the screen parameters look good. In this paper, the equipment, parameters and selection rules of each layer are disassembled according to the four-layer architecture, and the calculation and judgment basis that can be directly applied are given.

1. Four-tier Architecture Overview

The LCD splicing screen system is functionally divided into four levels. The responsibilities and key equipment of each level are as follows (according to the caliber of mainstream manufacturers, some manufacturers classify matrix and decoder into signal layer, and the selection is subject to the manufacturer's plan):

a word to understand the four levels of relationship:The signal layer is responsible for "sending the signal to", the processing layer is responsible for "processing the signal into a format that can be used by the splicing screen", the display layer is responsible for "displaying the picture", and the control layer is responsible for "telling each layer how to work together". Let’s now expand layer by layer.

2. display layer-the carrier of the final presentation of the picture

Core composition of the 2.1 display layer

• LCD Splicing Unit: Composed of LCD panel, driver board, power board, and interface board.
• Panel: Determine the basis of image quality, divided into industrial grade and commercial grade.
• Drive board: Receive the processing layer signal and drive the liquid crystal panel to display.
• Interface board: Provide HDMI, DVI, VGA, SDI, network port and other input interfaces.

2.2 Display Layer Key Parameters

2.3 the "inner spell" and "outer spell" of the display layer"

• Built-in splicing modulePart of the splicing unit has a built-in splicing processing function, and the signal division is directly completed through the drive board without an external processor, which is suitable for small splicing.
• External splicing treatment: All signals are uniformly distributed to each screen after entering the external processor, which is suitable for large splicing systems.

3. processing layer-the "brain" of the system"

Core equipment for the 3.1 processing layer

Video wall processorIt is the core of the processing layer and is responsible for cutting, scaling and splicing multiple signals and outputting them to each splicing unit. There are three types by architecture:

• Centralized architecture: A single host integrates all processing modules, and the input signals are collected at one point for processing and then distributed. The architecture is simple, stable and reliable, and has low latency, but there is a single point of failure risk, suitable for small and medium-sized local splicing.
• distributed architecture: Composed of input nodes, network switches, and output nodes. No separate server is required. The nodes can freely define input and output through software or dial codes. Suitable for signal dispersion, long-distance transmission, large-scale splicing.
• Hybrid Architecture: Centralized and distributed integration, taking into account the local signal low delay and remote signal network access.

matrix switcherResponsible for multi-channel signal to multi-output switching, typical specifications such as 16 in 16 out HDMI matrix, internal use of high bandwidth switch chip, support audio and video independent control. Key points of selection: number of input and output channels, resolution support (1080P/4K), seamless switching, control interface (RS232/TCP/IP).

DecoderIt is a necessary equipment for monitoring scene processing layer. It adopts embedded architecture and supports monitoring signal access of GB/T28181 and ONVIF standards. It can realize split display of multiple pictures on a single screen (common 4/9/16/32/64 split). Note: The multi-screen segmentation of the decoder is the display capability within a single screen. Whether to support cross-screen display varies with the manufacturer. It needs to be confirmed separately during selection. Key points for selection: number of decoding channels, decoding format (H.264/H.265), wall-to-wall method, and whether cross-screen support is supported.

Comparison of Three Typical Architectures of 3.2 Processing Layer

Selection of 3.3 treatment layer to avoid pit

• The processor bandwidth is not enough, 4K signal can not be on the wall-before selection, estimate the bandwidth according to the formula in Chapter 7 below.
• The number of decoder roads is not enough, and all monitoring points cannot be on the wall-the number of decoding roads is calculated by "simultaneous wall points", not by the total number of cameras.
• The matrix does not support seamless switching, and the screen is black when switching-the meeting room and command scene must be switched seamlessly.
• The distributed architecture network bandwidth is insufficient, and the picture is stuck-the core switch leaves more than 30% margin according to the bandwidth requirement.

4. control layer-the "nervous system" of the system"

Core functions of the 4.1 control layer

• Splice Management: Set the splicing method (M×N), window opening, roaming and picture-in-picture.
• signal scheduling: Switch the signal source and call the plan.
• Device Management: Large screen switch, brightness adjustment, mode switching.
• Environmental linkage: Linkage with central control equipment such as lights, air conditioners, curtains, etc.

4.2 Control Methods and Protocols

4.3 control software

Mainstream splicing screen control systems generally support browser-side unified management, common capabilities include:

• Visual operation: WYSIWYG signal preview, drag to add signal source, support window level, window, replace, zoom, roaming, overlay.
• Plan management: Support mode and plan management, switch scenarios with one click.
• multi-terminal synchronization: Web, tablet and client data are synchronized in real time.
• Remote Operations and Maintenance: Remote control of broadcast control host, some systems support voice control large screen operation (clear screen, switch plan, switch screen, etc.).

Key Points of B2B Selection for 4.4 Control Layer

• Whether remote control is required (unified management of multiple projects across regions).
• Whether it is necessary to interface with third-party systems (monitoring platform, information release system, central control system).
• Whether multi-user rights management is required.
• Whether plan and scenario management is required.

5. signal layer-the "blood vessels" of the system"

Core components of the 5.1 signal layer

5.2 Transmission Distance and Transmission Medium

Signal transmission distance directly determines the transmission medium selection, the following is the industry experience reference value:

Two Transport Architectures for the 5.3 Signal Layer

centralized transmission: Signal source → distributor/matrix → cable → splicing screen. Suitable for small systems, signal source and screen body close, simple architecture, low delay.

distributed transmission: signal source → encoding node → network switch → decoding node → splicing screen. Suitable for large systems, signal source dispersion, long-distance transmission, flexible expansion, simple wiring.

Key Points of B2B Selection for 5.4 Signal Layer

• Source type: HDMI, DVI, VGA, SDI, network stream.
• Transmission distance: determines cable and extender selection.
• Number of signal paths: Determines the distributor and matrix specifications.
• Whether redundant backup is required: whether the core link is dual-line/dual-switch.

Collaborative workflow 6. a four-tier architecture

Signal Uplink Process(Signal source → display): signal source → signal layer (transmission/distribution) → processing layer (cutting/splicing/switching) → display layer (display).

Control Downlink Process(operation end → each layer): operation end → control layer (command issued) → processing layer (switching/splicing) → display layer (response display).

Architectural differences in three typical scenarios:

• Monitoring Scenarios: Camera → NVR → decoder (processing layer) → matrix/processor → splicing screen (display layer), control layer is managed through TCP/IP. Key points: decoding path number, wall-to-wall mode and GB28181 compatibility.
• advertising scene: Cloud platform → playback box (processing layer) → distributor/matrix (signal layer) → splicing screen (display layer), the control layer is remotely managed through the information release system. Key points: remote release, timing switch, multi-store unified management.
• Conference Scene: Computer/screen caster/AI camera → matrix/processor (processing layer) → splicing screen (display layer), the control layer is managed by the central control software. Key points: wireless screen projection, seamless switching and interactive experience.

Calculation and Judgment Basis of 7. Architecture Design

This is the core chapter of this article, whether the scheme is reasonable, with the following three sets of calculations a priori again:

8. Common Problems and Misunderstandings in Selection

8.1 common architecture design issues

• Signal layer bottleneck: Too long cable causes signal attenuation, no extender or fiber is configured.
• Processing Layer Bottleneck: The processor bandwidth is insufficient, and the 4K signal cannot go to the wall.
• Control layer bottleneck: The control protocols are not compatible and cannot be managed uniformly.
• Display layer bottleneck: The screen does not support 7 × 24 operation, and there is a problem with long-term use.

Misunderstanding of 8.2 selection

• Only look at the screen parameters, ignoring the matching of the processing layer and the signal layer.
• Centralized and distributed error selection, resulting in wasted cost or insufficient performance.
• The number of decoder paths is calculated according to the total number of cameras, ignoring the caliber of "simultaneous wall paths.
• The control layer does not support the docking of third-party systems, and it is difficult to expand later.
• Improper selection of signal layer cable, signal attenuation occurs during acceptance.

9. FAQ

1. LCD splicing screen system must be equipped with processor?4-9 screen small system can be built-in splicing; More than 9 screens or need to open windows, roaming, picture-in-picture, must be external processor.
2. What are the centralized and distributed processors?Look at the scale and distance: 9-36 screens, signal concentration, local-based selection of centralized type; More than 36 screens, signal dispersion, cross-floor/cross-building selection distribution; Command center and other single-point failure unacceptable scenarios are preferred.
3. What is the difference between a decoder and a processor? Can they replace each other?The decoder decodes the monitoring signal into a picture and puts it on the wall; the processor is responsible for splicing, windowing, and roaming. Monitoring systems are usually both and cannot be replaced by each other.
4. Is the matrix necessary?Multi-channel signals need to be switched; simple advertising screens with a single signal source can be used.
5. What if the signal transmission exceeds 100 meters?Must use optical fiber; Priority cable extender within 100 meters and direct HDMI cable within 15 meters.
6. What control protocols does the control layer support?RS-232/RS-422/RS-485 serial port, TCP/IP/UDP network, IR infrared, I/O and RELAY central control linkage.
7. Does a distributed architecture require a separate server?Mainstream distributed node design, no separate server, input and output nodes through the switch interconnection.
8. Can the splicing screen system do remote operation and maintenance?The mainstream control system supports remote management, plan switching and equipment status monitoring on the Web side, and can uniformly control multiple projects across regions.
9. Monitor the wall with a decoder or a processor?Decoder for decoding the upper wall, processor for cross-screen splicing and window opening.
10. Does the ad splicing screen need a processor?A simple advertising screen with a single signal source is not required; it is only required when multiple screens are shaped and multiple signals are mixed.
11. Do small projects (4 screens) require a complete four-tier architecture?All four layers exist, but the built-in splicing distributor can be used to simplify the processing layer and the signal layer, and the control layer can use serial ports instead of a complete processor.
12. Does the structure need to be redesigned to expand the number of screens in the later period?Expanding 1-2 screens usually only requires adding screens and adjusting splicing parameters. When doubling the scale or crossing floors, the distributed design must be carried out in advance, otherwise it will have to be overturned and repeated.

10. summary: four-layer matching is the key to system stability

The display layer is "face", the processing layer is "brain", the control layer is "nerve", and the signal layer is "blood vessel". B2B splicing screen scheme design, can't just look at the screen parameters--The matching of the four-tier architecture is the key to the long-term stability of the system.. Before selection, use the three sets of formulas in Chapter 7 to check (number of processor paths, bandwidth, and number of decoding paths), and then determine whether it is centralized or distributed according to the architecture decision rules.