With the rapid development of LED display technology, small-pitch LED screens (such as P0.9, P1.2, P1.5, etc.) have gradually become the mainstream of the market. With their high resolution and seamless splicing characteristics, they are favored in command and dispatch, high-end meetings, virtual shooting and other scenes.
At the same time, the advent of the 4K/8K ultra-HD display era has put forward higher requirements for the picture quality of display terminals. Users not only pursue higher resolution, but also want to see more realistic colors, higher contrast and more delicate light and dark details.
In this context, High Dynamic Range technology has become the key to breaking through the display bottleneck. It gives small-pitch LED displays stronger picture quality restoration capabilities by enhancing the brightness range, expanding the color gamut depth and optimizing grayscale transitions. SightLED will explore the core advantages of HDR technology in depth.
Features and advantages of HDR technology
By breaking through the dynamic range limitations of traditional display devices, HDR technology significantly improves the realism and immersion of the picture.
Core advantages:
High dynamic range: perfect presentation of light and dark details
HDR supports higher peak brightness (usually 1000-4000 nits) and deeper black field performance (less than 0.05 nits). The dynamic range can reach more than 10 times that of ordinary SDR (standard dynamic range). For example, when showing buildings under sunlight, HDR can clearly present the texture of the highlight part while retaining the details of the shadow area to avoid overexposure or dead black.
Wide color gamut and high color depth: accurate color restoration
HDR is usually combined with Rec.2020 or DCI-P3 wide color gamut standards to cover more real colors in nature. With 10bit/12bit color depth technology, it can achieve a smooth transition from 1 billion to 68 billion colors. Therefore, this technology can completely solve the color fault problem caused by traditional 8bit color depth.
Frame-by-frame metadata processing: intelligent optimization of picture performance
HDR metadata (such as HDR10+ dynamic metadata) can record the brightness and contrast information of each frame. Therefore, the display can adjust parameters in real time according to the content to achieve the best display effect in different scenarios.
Challenges of HDR implementation on small-pitch LED display
Although HDR technology has significant advantages, its implementation on small-pitch LED screens requires overcoming the complexity of hardware architecture, signal transmission and system coordination.
Hardware architecture: driving challenges brought by high-density lamp beads
Take the P1.2 small-pitch LED screen as an example, the number of lamp beads in a single cabinet (such as 500mm×500mm) can reach 430,000. It is more than 4 times that of a conventional P2.5 screen. The traditional “one cabinet and one receiving card” design can no longer meet the driving requirements, and a “one cabinet and multiple cards” solution (such as 2-4 receiving cards) is required.
In addition, the reduction in the spacing between lamp beads puts higher requirements on PCB wiring, heat dissipation design and power supply stability. For example, too dense routing may cause signal crosstalk, and multilayer board design and impedance matching technology are required.
Signal transmission: bandwidth pressure and connection method innovation
The number of pixels of small-pitch LED screens is growing exponentially. Taking 4K resolution (3840×2160) as an example, the number of pixels of a single screen exceeds 8 million, which puts strict requirements on the transmission bandwidth.
Conventional LED screens use arbitrary routing (as shown in Figure 1), and each network cable can carry about 650,000 pixels. Small-pitch screens need to use vertical routing (as shown in Figure 2) and transmit in parallel through multiple network cables. For example, for the same area of display screen, ordinary screens use 3 network cables, while P1.2 small-pitch LED screens require 5 network cables, and they must be arranged strictly in the vertical direction to avoid bandwidth bottlenecks.
(Note: vertical routing reduces transmission delay and interference by optimizing the signal path)
Implementation path of HDR on small dot pitch LED screen
The current mainstream HDR implementation solutions in the industry are divided into two categories: front-end processing based on video processors and back-end processing based on sending cards. Both solutions have their own advantages and disadvantages, and need to be flexibly selected according to the application scenario.
Solution 1: HDR video processor driver
Video processor solution architecture
Implementation process:
- HDR source input: support 4K/8K video sources in formats such as HLG, HDR10, Dolby Vision, etc. to access the video processor.
- Decoding and mapping: The processor completes HDR metadata parsing and maps the signal to the brightness/color gamut range of the LED screen (such as PQ curve conversion).
- Screen segmentation and output: The screen is divided into multiple splicing areas through FPGA or dedicated chips, and transmitted to the receiving card through the sending card.
Advantages:
- Strong compatibility: It can adapt to sending cards and receiving cards of different brands.
- Flexible processing: supports multi-format HDR dynamic metadata parsing.
Limitations:
- The system has high latency (usually >2 frames), which is not suitable for real-time interactive scenarios.
- The cost is high, and a high-end video processor needs to be purchased separately.
Solution 2: Full-link processing of HDR sending card
Implementation process:
- Directly input HDR signal: HDMI 2.1 or 12G-SDI interface directly transmits HDR source to the sending card.
- Integrated encoding and decoding: The sending card has a built-in HDR decoding engine, embeds metadata into the video stream, and marks the HDR logo through a private protocol.
- Receiving card collaborative drive: The receiving card calls the preset HDR gamma curve and color lookup table (LUT) according to the logo to drive the LED lamp beads.
Advantages:
- Low latency (<1 frame), suitable for real-time scenarios such as broadcasting and television live broadcasting, virtual shooting, etc.
- Cost optimization: No external processor is required, and the system integration is higher.
Challenges:
- Customized development of sending card and receiving card firmware is required, and the ecosystem is closed.
- The stability of the transmission link is extremely high, and shielded network cables and redundant designs are required.
Sight HDR technology solutions for small-pitch LED screens
For the pain points of HDR implementation of small-pitch LED screens, Sight HDR has proposed a full-link optimization solution, covering three modules: hardware design, signal processing, and color management.
1. Hardware innovation: distributed receiving card architecture
Adopting the “one box and four cards” design, each receiving card independently drives 1/4 area, and ensures picture consistency through synchronous clock signals. At the same time, the integrated intelligent power management chip (IPM) monitors the current fluctuation of each lamp bead in real time, and controls the brightness deviation within ±2%.
2. Transmission optimization: adaptive bandwidth allocation technology
By dynamically adjusting the load of each network cable (supporting up to 850,000 pixels/line), the number of network cables required for vertical routing is reduced. For example, the number of network cables for a P1.2 screen can be reduced from 5 to 3, while supporting asymmetric routing to improve wiring flexibility.
3. Color engine: 3D-LUT dynamic calibration
Built-in 17×17×17 three-dimensional lookup table, combined with HDR metadata to generate color mapping curves in real time. For example, when playing Dolby Vision content, the system automatically matches 12-bit color depth and 10000:1 contrast parameters to ensure cinema-level color reproduction.
Conclusion
From the perspective of technological evolution, HDR technology has become a “standard” capability for small-pitch LED screens. It not only solves the bottleneck of image quality under high-density display, but also expands application scenarios through a more realistic visual experience. From real-time background rendering in virtual production to accurate color presentation of medical images, the value of HDR is being redefined.
In the future, with the maturity of Micro LED technology and the popularization of 8K sources, HDR technology will be further combined with AI image enhancement, dynamic tone mapping (DTM), etc., to promote the continuous evolution of small-pitch LED screens towards “extreme reality”. And full-link solutions like Sight HDR will provide key support for companies to seize the high-end display market.
