Technical Renovation of 4K Laser Projection and Surround Sound Systems: A Case Study of the Film Screening Room at Guangxi Radio and Television Station

Guangxi Radio and Television Station, Nanning, Guangxi Zhuang Autonomous Region, 530022

Abstract

[Objective] As film industrialization accelerates, film screening rooms—critical nodes for quality control—have experienced persistent technological lag behind innovations in production-side technologies. [Methods] This study examines the film screening room at Guangxi Radio and Television Station, addressing technical bottlenecks identified during the review process, including optical performance degradation in the projection system, surround sound system deficiencies, and insufficient system compatibility. A comprehensive technical renovation was implemented. [Results] Engineers successfully established a high-fidelity technical verification platform aligned with film industrialization production standards by adopting Digital Cinema Initiatives (DCI) Specification Version 1.0 as the core framework, focusing on coordinated upgrades of the 4K laser projection system and immersive surround sound system, and reconstructing system compatibility. [Conclusion] This project validates the applicability of DCI standards in regional film screening room renovations, provides a reusable technical pathway for similar facilities, and offers valuable reference for promoting end-to-end technological synergy across the entire film industry chain.

Keywords: film screening; DCI standards; 4K laser projection; immersive audio; system compatibility
Classification Code: G222
Document Code: A
Article ID: 1671-0134(2025)05-150-05
DOI: 10.19483/j.cnki.11-4653/n.2025.05.033
Citation Format: Feng Xiaochuan. Technical Renovation of 4K Laser Projection and Surround Sound Systems: A Case Study of the Film Screening Room at Guangxi Radio and Television Station [J]. China Media Technology, 2025, 32(5): 150-153, 158.

The film screening room at Guangxi Radio and Television Station serves as a critical facility for film review in the Guangxi Zhuang Autonomous Region and has been in operation for over a decade. In recent years, technical limitations have directly impacted the objectivity and accuracy of film reviews: the xenon lamp projection system suffered from insufficient resolution, optical performance degradation, and color reproduction deficiencies. The surround sound system exhibited significant hardware performance flaws, including missing vertical sound fields and mismatched channel configurations for the space. System compatibility issues, hardware interface conflicts, and outdated protocol standards required technical downgrading of review copies to accommodate the screening system, resulting in data loss and inability to faithfully reproduce the production quality of submitted films. The lack of automatic switching between primary and backup links necessitated manual interface switching during failures, disrupting the continuity and security of the review process.

China's film industry has achieved generational technological leaps in recent years, developing a globally competitive industrial system. The 2025 animated film Ne Zha: The Demon Child represents a milestone in China's animation industrialization, continuously breaking world box office records and marking a historic transition from technology import to paradigm export. Guo Fan's team pioneered a new paradigm for domestic sci-fi film industrialization in the Wandering Earth series, while the integration of authentic racing footage with CG technology in Pegasus brought the excitement of rally racing vividly to the screen. As China's film industrialization workflow matures and projection technology and viewing experiences advance, the demand for end-to-end technological synergy across the "production-review-exhibition" chain has become increasingly urgent. In May 2024, the National Development and Reform Commission, Ministry of Housing and Urban-Rural Development, Ministry of Culture and Tourism, National Film Administration, National Radio and Television Administration, and National Cultural Heritage Administration jointly issued the Implementation Plan for Promoting Equipment Renewal in Culture and Tourism \cite{1}, explicitly proposing strategic goals to "promote quality upgrades in film production, enhance overall film production standards, and advance independent innovation in film projection technology," highlighting the importance of full-chain technological synergy. However, the review stage—as the core node for content review and technical quality control—has lagged behind production-side technological innovations, creating a pain point in the industry chain.

To address these challenges, this paper proposes a technical renovation of the 4K laser projection and surround sound systems using the DCI (Digital Cinema Initiatives) standard \cite{2} as the core framework. Established in 2002 by Hollywood's seven major studios—Disney, Fox, MGM, Paramount, Sony Pictures, Universal, and Warner Bros.—the DCI standard provides a comprehensive technical specification for digital cinema. Spanning the entire digital cinema production workflow, it achieves efficient standardization and quality control from production and distribution to exhibition, offering a high-performance, high-reliability technical architecture \cite{3}. The DCI standard provides engineers with crucial guidance for developing technical solutions \cite{4}, enabling the construction of a high-fidelity technical verification platform that matches film industrialization production standards.

1. System Design and Technical Implementation

1.1 4K Laser Projection System Upgrade

1.1.1 Problem Analysis and Technical Requirements

(1) Insufficient Native Resolution and High Motion Blur Index
The original xenon lamp projection system only supported 2K (2048×1080) native resolution, requiring interpolation to output 4K (4096×2160) resolution. The Motion Blur Index (MBI) was high, resulting in insufficient image clarity. The DCI standard requires digital projection systems to natively support DCI 4K resolution and be compatible with high frame rate formats of 24/48 fps.

(2) Light Source and Brightness Gain Mismatch
The original xenon lamp projector suffered from severe light source brightness degradation and insufficient screen illumination, particularly noticeable at screen edges when viewing 3D films. The mismatch between the projector and screen gain optical architecture resulted in poor brightness uniformity, low contrast, and missing dark-field details. The DCI standard requires projection system light sources to maintain brightness degradation within reasonable thresholds during their rated lifespan, not exceeding 30% of initial values, with light output efficiency matched to screen gain to ensure brightness differences between screen center and edges remain ≤15%, preventing localized over-bright or over-dark areas.

(3) Insufficient Color Gamut Coverage
Due to mismatched spectral characteristics between the xenon light source and metal screen reflection properties, the projection system exhibited inadequate color gamut coverage and peak brightness, causing color reproduction deviations and loss of HDR highlight details. The DCI standard mandates that projection systems natively support the DCI-P3 color gamut with chromaticity coordinate error Δu'v'≤0.015 to avoid image distortion from color shifts and ensure accurate color reproduction of submitted film masters.

1.1.2 Upgrade Solution and Technical Implementation

To simultaneously meet DCI standard requirements for "resolution-optical performance-color" quality, engineers implemented a coordinated design using the Barco SP4K-35B laser projector \cite{5} and Harkness Clarus XC170 screen \cite{6} to construct a new optical imaging system, as shown in Table 1 [TABLE:1]. The Barco SP4K-35B laser projector is illustrated in Figure 1 [FIGURE:1].

Table 1 Main Technical Parameters of Projection System Equipment
- Barco SP4K-35B Laser Projector: RGB laser light source, 35,000 lumens stable output, dynamic contrast ratio (2000:1), native 4K (4096×2160) resolution per eye, DCI-P3 color gamut coverage reaching 98.5% of Rec.2020 standard, HDR 12-bit color depth supporting 68.7 billion colors
- Harkness Clarus XC170 Screen: 1.7 gain, micro-perforated acoustic design (aperture ≤0.6mm), curved metal screen design enhancing reflectivity and light distribution

1.1.3 Synergistic Effects and Performance Improvements

(1) Resolution Enhancement
The Barco SP4K-35B laser projector's 4K DMD chip supports native 4K (4096×2160) resolution and native DCI standard frame rates (24/48/60/120 fps), eliminating edge artifacts and motion blur issues from interpolation-based 4K output in the original system and ensuring image clarity meets DCI standards. The Clarus XC170 screen's micro-perforated design and Nanolast™ optical coating better adapt to the Barco SP4K-35B's native 4K resolution projection, effectively reducing inter-pixel interference and enhancing image sharpness to present richer detail.

(2) Optical Performance Optimization
The Barco SP4K-35B's RGB laser light source stably outputs 35,000 lumens with a dynamic contrast ratio of 2000:1. This ultra-high brightness and high dynamic contrast are key to optimizing projection system optical performance. The high-performance light source combined with the Clarus XC170 screen's 1.7 gain not only reflects more light but also enhances dark detail representation. The screen's curved structure design optimizes light path reflection efficiency, reduces brightness differences between screen center and edges, and improves brightness uniformity. The new optical imaging system employs polarized 3D technology with coordinated design among the projector, high-gain screen, and polarized 3D glasses to compensate for light splitting losses, enhance brightness and depth performance in 3D mode, and improve immersive stereoscopic imagery, systematically resolving the original system's optical performance deficiencies.

(3) Color Performance Upgrade
RGB tri-color laser technology represents the leading light source technology in the film and television industry. The Barco SP4K-35B laser projector achieves ΔE<2, surpassing even the stringent DCI standard requirements in spectral purity and color accuracy. Its color gamut coverage reaches DCI-P3, encompassing 98.5% of the ultra-high-definition color gamut standard (Rec.2020), providing an extremely rich color performance space. With HDR 12-bit color depth supporting 68.7 billion colors, it improves smoothness in color gradient scenes (e.g., light-shadow transitions, sky rendering), solving HDR color banding issues. After the color performance upgrade, the system fully adapts to current film industrialization production color technologies and can accurately reproduce the color of submitted film masters.

2. Surround Sound System Renovation and Immersive Sound Field Construction

2.1 Technical Bottlenecks in Immersive Sound Field Construction

(1) Missing Vertical Sound Field
The Guangxi Radio and Television Station screening room measures 20 meters long, 14 meters wide, and 10 meters high. Due to insufficient ceiling load-bearing capacity, overhead speakers could not be deployed, resulting in lost vertical sound field information. The DCI standard requires uniform sound field distribution in theaters, with vertical pressure level differences controlled within ±3dB to ensure seamless energy distribution between overhead and horizontal channels and avoid ambiguous height sound image localization.

(2) Surround Sound System Performance Defects
The original system's outdated codec model exhibited significant protocol generation gaps, only supporting Dolby Digital (5.1/7.1) channel decoding and unable to parse current mainstream immersive audio formats such as Dolby Atmos or DTS:X. Submitted film masters required technical downgrading to accommodate the screening system, causing data loss. The DCI standard mandates system support for IAB (Immersive Audio Bitstream) format to ensure full compatibility with immersive audio technologies.

(3) Equipment Mismatch Issues
The surround sound system's audio processor, amplifiers, and speakers were not precisely matched, failing to achieve optimal performance叠加 (superposition). When reviewing high-quality film masters, issues emerged including power and impedance mismatch, dynamic range compression, and frequency response phase misalignment, preventing faithful reproduction of submitted film master quality and directly impacting review objectivity and accuracy.

2.2 System Architecture and Technical Implementation

The renovation technical solution was designed around the QSC Q-SYS platform system \cite{7}.

(1) Q-SYS Platform Three-Dimensional Sound Field Reconstruction
Reconstructing the three-dimensional sound field was a critical objective of this screening room renovation. Engineers innovatively applied QSC Q-SYS platform's virtual height sound field mapping technology \cite{8} to achieve this goal. The principle of virtual height sound field mapping involves parsing immersive audio metadata for vertical sound field parameters through QSC's Spatial Acoustic Mapping algorithm \cite{9}, then mapping signals to the horizontal surround speaker array based on sound source elevation angles and energy distribution. Adapting to the screening room's physical constraints, engineers reconstructed a three-dimensional sound field with height层次感 (layering) without ceiling-mounted speakers.

The Q-SYS platform's time-domain equalization technology adjusts sound signal temporal characteristics to eliminate acoustic delays caused by speaker position differences or room reflections, preventing sound "smearing" or phase shifts. Gain compensation technology dynamically adjusts volume ratios across channels based on coverage range and energy attenuation characteristics of different speakers. For example, gain compensation can dynamically enhance output energy of specific horizontal speakers based on different sound source heights, compensating for high-frequency loss due to insufficient vertical dispersion while suppressing sound distortion in high-volume scenes to ensure clarity in loud dynamic effects like explosions.

In implementation, engineers deployed 12 DCS-SR-1590 surround speakers (4 each on left/right/rear walls) to form a horizontal surround array based on acoustic modeling for three-dimensional sound image localization \cite{10}. Using the Q-SYS Core 110F processor with virtual height sound field mapping technology, combined with room acoustic modeling and film master audio metadata parsing, high-precision three-dimensional sound field reconstruction was achieved. Coordinated use of time-domain equalization and gain compensation technologies \cite{11} systematically resolved phase distortion, uneven energy distribution, and dynamic range compression issues in three-dimensional sound field reconstruction \cite{12-13}.

(2) Acoustic Performance Optimization
Employing a modular design concept, the system achieved DCI standard requirements for dynamic range and frequency response through coordinated configuration of main channels, low-frequency compensation, and power drive units. The main channels deployed three QSC SC-424 speaker groups (left/center/right) \cite{14}. The QSC SC-424 speakers feature a three-way acoustic design with dual woofer units and waveguide-driven mid-high frequency components, achieving optimized multi-band phase consistency. Matched design of horizontal coverage angles and sensitivity parameters maintains dialogue clarity and background sound separation in complex acoustic environments, ensuring distinct dialogue layers and clear, pleasant voice-overs.

For low-frequency design, four DCS-SB-7218 subwoofer speakers \cite{15} with dual 18-inch symmetrically arranged units were deployed, optimizing spatial balance of low-frequency energy through cabinet structure design. Special inverted-phase port and internal damping layer designs preserve impactful energy for explosion and collision effects while avoiding low-frequency standing wave interference with mid-high frequencies. Two QSC DCS-SB-2180 subwoofer speakers \cite{16} serve as mid-low frequency transition units using short-stroke linear drive technology to strengthen frequency transition between main speakers and subwoofers, ensuring detailed mid-low frequency restoration.

Using QSC SC-424 speakers combined with DCS-SB-7218 subwoofers and the Low-Frequency Phase Correction (LFC) algorithm, engineers corrected multi-band phase offsets through dynamically optimized phase synchronization and energy ratios. This enhanced temporal consistency for composite effects like explosions and collisions, suppressed non-linear distortion in high-dynamic scenes to preserve purity of mid-high frequency dialogue and background effects, and balanced low-frequency energy distribution to strengthen separation between sub-bass and mid-bass layers, achieving high-fidelity restoration of submitted film master sound fields and improving review objectivity and accuracy.

The QSC surround speaker array is shown in Figure 2 [FIGURE:2].

3. System Compatibility Upgrade and Optimization

In system compatibility upgrades, a hierarchical compatibility architecture was constructed based on DCI standard requirements for signal transmission redundancy, protocol uniformity, and system scalability.

The Barco SP4K-35B laser projection system features DCI-certified 12G-SDI and HDMI 2.1 dual-link transmission architecture, achieving seamless signal source switching through redundant design of the Barco ICP-D projection server. Engineers built a QSC Q-SYS platform dual-machine hot backup system, implementing primary-backup audio link redundancy transmission and automatic hot switching through the Q-SYS Core 110F processor's intelligent redundancy control module. Adopting the unified AES67 transmission protocol avoided issues such as audio stream timestamp conflicts and metadata parsing errors, meeting DCI standard requirements for audio redundancy, protocol consistency, and audio-visual synchronization, significantly enhancing system capability to parse and restore complex soundtracks from submitted film masters.

The entire system employs modular design, supporting dynamic hardware resource expansion and software function iterative upgrades. It flexibly adapts to different format signal processing requirements, provides underlying architecture support for future 8K ultra-high-definition, high frame rate, and panoramic sound technology upgrades, and ensures continuity and stability of the review process.

Following the technical renovation of the 4K laser projection and surround sound systems, the Guangxi Radio and Television Station film screening room has undertaken technical review of numerous Guangxi-produced films including A Beautiful Life, Jasmine Flower, and The Nightingale. Jasmine Flower, adapted from the true story of He Yue, a primary school student from Yangshuo, Guilin, who donated organs to save three lives and was honored in CCTV's 2012 "Touching China" awards, holds significant meaning for promoting national organ donation policies and socialist core values. A Beautiful Life, based on the story of Huang Wenxiu—a national role model in poverty alleviation—underwent rigorous technical quality control under the coordination of the Guangxi Autonomous Region Party Committee Propaganda Department. Through precise restoration of ethnic elements, natural light and shadow, and humanistic textures from northwestern Guangxi villages, the film presented authentic and vivid characters, earning 12 honors including the Golden Rooster Award for "Best Small-Medium Cost Feature Film" and establishing a regional benchmark for mainstream film creation.

Through technical performance upgrades and system compatibility reconstruction, the Guangxi Radio and Television Station film screening room has systematically resolved the technological gap between film review processes and production-side capabilities, validating the engineering applicability of DCI standards in regional screening room renovations. This provides a reusable technical pathway for full-chain technological synergy in the film industry and offers valuable reference for similar screening room construction and technical upgrade projects.

References

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Author Information: Feng Xiaochuan (1988—), male, Nanning, Guangxi, graduate student, professional engineer in radio, film, and television technology engineering. Research direction: radio, film, and television technology engineering.