CEA Standard. BTSC System Multichannel Television Sound Recommended Practices CEA-TVSB-5 S-2015

Transcription

1 CEA Standard BTSC System Multichannel Television Sound Recommended Practices CEA-TVSB-5 S-2015 July 1985

2 NOTICE Consumer Electronics Association (CEA ) Standards, Bulletins and other technical publications are designed to serve the public interest through eliminating misunderstandings between manufacturers and purchasers, facilitating interchangeability and improvement of products, and assisting the purchaser in selecting and obtaining with minimum delay the proper product for his particular need. Existence of such Standards, Bulletins and other technical publications shall not in any respect preclude any member or nonmember of CEA from manufacturing or selling products not conforming to such Standards, Bulletins or other technical publications, nor shall the existence of such Standards, Bulletins and other technical publications preclude their voluntary use by those other than CEA members, whether the standard is to be used either domestically or internationally. Standards, Bulletins and other technical publications are adopted by CEA in accordance with the American National Standards Institute (ANSI) patent policy. By such action, CEA does not assume any liability to any patent owner, nor does it assume any obligation whatever to parties adopting the Standard, Bulletin or other technical publication. This document does not purport to address all safety problems associated with its use or all applicable regulatory requirements. It is the responsibility of the user of this document to establish appropriate safety and health practices and to determine the applicability of regulatory limitations before its use. This document is copyrighted by the Consumer Electronics Association (CEA ) and may not be reproduced, in whole or part, without written permission. Federal copyright law prohibits unauthorized reproduction of this document by any means. Organizations may obtain permission to reproduce a limited number of copies by entering into a license agreement. Requests to reproduce text, data, charts, figures or other material should be made to CEA. (Formulated under the cognizance of the CEA R4 Video Systems Committee.) Published by CONSUMER ELECTRONICS ASSOCIATION 2015 Technology & Standards Department All rights reserved

3 PREFACE These recommended practices on the BTSC system for multichannel television sound (MTS) have been prepared by the Ad hoc working Group of the Multichannel Sound Subcommittee's Steering Committee of the EIA Engineering Department's Broadcast Television Systems Committee. This bulletin is intended to be a living document. Users may find in it what they consider incomplete or unclear information suggestions for the next edition are invited. They should be sent to:

4 BTSC SYSTEM MULTICHANNEL TELEVISION SOUND RECOMMENDED PRACTICES Table of Contents Page 1. Introduction Scope Description of the system and its protection Definitions Miscellaneous Definitions Definitions Relating to Buzz Interference TRANSMISSION SYSTEM Visual Transmitter Buzz Interference, Transmitter Issues Background Definitions Buzz Interference Sources Spurious Phase Modulation of the 16 Visual Carrier Visual Splatter into the Sound 18 Channel: Spectral Overflow Transfer of Visual Distortions to 18 To the Sound Channel Receiver Considerations Incidental Carrier Phase Modulation (ICPM) Video Modulation Levels Vertical Interval Signals Protection Against Spectral Overflow Video Filtering 26

5 2.2 Aural Transmitter Aural Transmitter Baseband Phase and Amplitude Tolerance Peak Deviation Capability Distortion and Crosstalk Noise Visual/ Aural Carrier Power Ratio System Levels and Modulation Calibration Stereo SAP Non- Program Related Subchannel Operation Television Transmitter Facility External Diplexing Requirements Internal Visual/ Aural Diplexing Requirements Aural Carrier Frequency Tolerance Standard Video Test Signals and Patterns for 38 Buzz Measurement RF transmission and Antenna Considerations Monophonic Transmitter Compatibility Aural Composite Generation Filter Requirements Left and Right Audio Input Filters (L+R) and (L-R) Audio Lowpass Filters (L+R) Preemphasis Network The BTSC Sum Channel Compensator Insertion Loss Equivalent Stereo Separation 58 2

6 Main Channel Amplitude Response Main Channel Amplitude Response SAP Subchannel Bandpass Filtering BTSC Stereo Generator Companding Algorithm Definition Standard Fixed Preemphasis Wideband- RMS- Detector 63 Bandlimiting Wideband-Amplitude- 64 Compressor Action Spectral-RMS- Detector 64 Bandlimiting Spectral Compressor 66 Action Fixed Deemphasis Wideband-Amplitude- 66 Expander Action Spectral- Expander Action Decibel RMS Value Method of Measurement Discussion Level Setting Pilot Phase Pilot Phase vs. Horizontal Phase Pilot Stereophonic Subcarrier 69 Phase Difference Stereo Separation With and Without Companding Interconnections Interface Standards 71 3

7 2.5.2 Studio Transmitter Link (STL) Translators MONITORING AND MEASURING (M&M) Visual Transmitter ICPM Measurement Capability Spectral Overflow Spectral Overflow in Externally 76 Diplexed Transmitters Spectral Overflow in Internally 76 Diplexed Transmitters 3.2 Aural Transmitter Aural Baseband Sound Detection Modes Split- Sound Monitoring 78 Mode Quasi-Parallel Sound 78 Detection Detected Aural Composite Baseband 79 Characteristics Aural Carrier Deviation Modulation Meters and Peak Flashers Main Channel Main Channel Characteristics Main Channel Distortion Main Channel Noise Crosstalk Into a Main Channel Filter Requirements Stereo Stereo Decode Characteristics 87 4

8 Pilot Injection Level Pilot/Interference Ratio Pilot to Stereophonic Subcarrier 89 Phase difference Pilot/Horizontal Lock and Phase Pilot Detection, Subcarrier 90 Regeneration Stereo Separation With and Without 91 Companding FM Noise Floors (L-R) Distortion Measurements Crosstalk into Stereo Subchannel Spurious Subcarrier Level Filter Requirement Matched Deemphasis Networks Second Audio Program (SAP) SAP Decoder Characteristics SAP Noise Floor SAP Distortion Crosstalk into SAP SAP Subcarrier Frequency/Lock Filter Requirements Aural Expanding Expander Expander Compensator Network (Main 105 Channel, Stereo Mode) Alignment of Expander Routine Expander/ Monitor Adjustments 107 5

9 Filter and Network Requirements Stereo Monitor Expander 107 Lowpass Filter SAP Monitor Expander 108 Lowpass Filter Microseconds De- 108 emphasis Non program related Subcarriers Remote Monitoring RECIEVER ISSUES Issues Important to Broadcasters and 110 Receiver Manufacturers Pilot Threshold SAP Threshold Issues Important to Receiver and Monitor 110 Manufacturers Buzz Interference Receiver Aspects Receiver Types Receiver Sensitivity to 111 Incoming Buzz Sources Buzz Sources in the Receiver Monitoring and Measuring Consumer-type Receivers Expander Filtering Expander Lowpass Filter Stereo Expander Lowpass Filtering SAP 116 6

10 5. APPENDICES Al. The use of subcarrier frequencies in the aural baseband of television transmitters, Second Report and Order FCC Docket No (RM-2836), released April 23, Erratum released June 26, A2. OST Bulletin No.60, Multichannel sound transmission and audio processing requirements for the BTSC system (April 1984). B. 75 us equivalent input modulation; L.B.Tyler. C. RF transmission and antenna considerations; J.J. Gibson. D. Relations between amplitudes and phases of the stereophonic difference encoded signal "D" and the stereophonic sum modulating signal "M" in the BTSC system when a sinewave feeds the left input; J.J. Gibson. E. A companding system for multichannel sound (A tutorial on companding); L.B.Tyler, et al. IEEE Transaction on Consumer Electronics, November 1984, Volume CE-30, Number 4. Reproduced with permission. F. Filter requirements in TV multichannel sound; Pieter Fockens. G. Aural carrier deviation by composite stereo -need for calibration; Pieter Fockens. H. Pilot protection in the BTSC system; Pieter Fockens. I. A proposed test signal for measuring crosstalk between subchannels; J.J. Gibson. J. BTSC companding programs -DEBEX; J.J. Gibson. K. Calculations of expander noise reduction and noise pumping in the presence of signals; J.J. Gibson. 7

11 6. REFERENCES 1. EIA Multichannel Sound Reports Volume I, published by the National Association of Broadcasters, July 16, Volume l-a, published by the National Association of Broadcasters, November 9, Supplement to Volumes l-a and 2-A, published by Electronic Industries Association, December 5, Compandor Complexity Analyses, published by Electronic Industries Association, December 12, Zenith Separate Audio Program Generator; Multipath Buzz and Distortion Investigation; Alpha-Omega Engineering, Inc. Statement, published by Electronic Industries Association, December 19, Volume 2, published by Electronic Industries Association, Consumer Electronics Group, August 6, Volume 2-A, published by Electronic Industries Association, November 5, Electrical performance standards for TV transmitters (To be published as EIA-508). 3. Recommended Practice for Audio Program Level Measurement (Draft in preparation by IEEE G 2.1.2, Audio Measurements Subcommittee). 4. Electrical Performance Standards for Television Broadcast Demodulators, EIA RS-462 (May, 1979). 8

12 1. INTRODUCTION 1.1. Scope This document is intended to serve the industry in the form of recommendations for anyone wishing to practice multichannel television sound (MTS) in accordance with the BTSC system and the FCC Rules governing its use. Both the FCC Report and Order in Docket which authorized MTS, and the OST Bulletin No.60 (OST 60 gives a technical description of the BTSC system) referred to in that report are reproduced in Appendix A. This document is intended for equipment manufacturers and broadcasters. For manufacturers, there is discussion material useful to determine design tradeoffs together with recommended performance standards. For broadcasters, there is discussion and information, which allows individual equipment items to be defined in terms of performance so that the transmitter plant will perform properly as a system. Receiver issues are identified which are of particular significance to the broadcaster as well as to the receiver manufacturer. While there is herein much useful information for the CATV industry, this document does not directly address the CATV MTS application. 1.2 Description of the System and Its Protection The transmission standards are graphically illustrated in Figure and summarized in Table 1.2. More detailed system standards are found in OST 60 and the total system block diagram in Figures and The main-channel aural-carrier modulation consists of an (L+R) audio signal. It is subjected to 75 us preemphasis. The (L-R) audio signal is subjected to compression (the transmitter part of the companding system that includes complementary expansion in the receiver). The compressed (L-R) signal causes double-sideband, suppressed-carrier amplitude modulation of a subcarrier at 2f H where f H is the transmitted picture horizontal scanning frequency, khz. The audio bandlimits of both preemphasized (L+R) and of encoded (L-R) are 50 Hz and 15 khz. The main channel peak deviation is 25 khz. The stereophonic subchannel peak deviation is 50 khz. When L and R are statistically independent, the combined peak deviation of the main channel and the stereophonic subchannel is also 50 khz when full interleaving exists. When (L+R) and (L-R) signals do not have matching pre-emphasis characteristics (as is the case when (L-R) is compressed), the combined deviation of main channel and stereophonic subchannel is constrained to 50 khz. The separate components assume their respective natural levels as dictated by the acoustic scene. 9