Overview
IEC 60856:1986/AMD2:1997 is Amendment 2 to the international standard IEC 60856, issued by the International Electrotechnical Commission (IEC). This amendment focuses on the pre-recorded optical reflective videodisk system known as "Laser Vision," specifically for 50 Hz/625 lines PAL video systems. It addresses updated mechanical, optical, temperature, humidity, video, and audio parameters to enhance the functionality and interoperability of videodisk systems. The amendment is essential for manufacturers and developers working with optical videodisk technology ensuring compliance with global standards in the audio-video industry.
Key Updates and Topics
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Mechanical Parameters
- Disk thickness requirements are precisely defined (min. 1.1 mm, max. 1.4 mm for single disks).
- Label specifications cover size, position, and thickness to ensure proper disk handling and operation.
- Clamping area thickness requirements are established for both single and double-sided disks, critical for drive compatibility.
- Maximum radial angle of the disk surface is limited to ±1° to maintain accurate optical reading.
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Optical Requirements
- Birefringence of transparent disks is capped at 40°, ensuring optical clarity and signal integrity.
- Numerical aperture of the readout laser beam lens standardized at NA = 0.40 ± 0.01 to optimize playback quality.
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Environmental Conditions
- Disks must withstand temperature ranges from 5 °C to 45 °C and humidity levels from 5% to 90% for four consecutive days without performance degradation.
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Video Signal Specifications
- Vertical Interval Test Signals (VITS) incorporated as per ITU-R Recommendation 473-5 to facilitate quality control and troubleshooting.
- Specific video lines are reserved for address and data signals, subtitles, and future applications while maintaining compatibility with PAL video standards.
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Digital Audio Signal Implementation
- Detailed introduction of digital audio signal modulation in the Laser Vision system as an optional enhancement, referencing IEC 60908 for the EFM signal structure.
- Signal processing includes low-pass and high-pass filtering, pre-emphasis, and symmetrical double-edge pulse width modulation to ensure high fidelity audio encoding.
- Block Error Rate (BLER) standards specified to guarantee error control in digital audio data transmission.
- Sample frequency standardized relative to the PAL line frequency, ensuring audio-video synchronization.
- Compensation techniques recommended to offset audio decoding delay for seamless playback.
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Sub-code and Command Signaling
- Specific modifications to sub-code modes ensure compatibility with compact disc standards for control and display commands within the video disc environment.
- Directory structure and table of contents (TOC) formatting align with IEC 60908-2 requirements to facilitate multimedia integration.
Applications
This amendment serves practical value for:
- Optical disc manufacturers refining product specifications to comply with up-to-date international mechanical and optical requirements for PAL Laser Vision discs.
- Video system designers and engineers integrating advanced digital audio capabilities alongside analog video on pre-recorded discs, improving media versatility.
- Quality control and testing labs applying the standardized vertical interval test signals and environmental resilience criteria to ensure product durability and performance.
- Multimedia content producers who rely on precise addressing, subtitling, and data embedding within the video stream for enhanced user experiences.
- Playback equipment developers ensuring device compatibility with amended specifications to deliver optimal reading and decoding of both video and digital audio signals.
Related Standards
- IEC 60908 – Digital audio tape and compact disc systems, complementary reference for audio signal implementation and modulation.
- ITU-R Recommendation 473-5 – Guidance on vertical interval test signals relevant for video quality assessments incorporated into this amendment.
- IEC 60856 (original and previous amendments) – Base standard for pre-recorded optical reflective videodisk systems, important for full technical understanding.
By aligning videodisk products with IEC 60856:1986/AMD2:1997 standards, manufacturers and developers ensure global interoperability, enhanced audio-visual quality, and robust mechanical and environmental performance in Laser Vision PAL systems. This amendment facilitates continued innovation and consistency in the optical media industry.