Maintaining Audio Quality in the Broadcast and Netcast Facility 2019 Edition Robert Orban Greg Ogonowski Orban®, Optimod®, and Opticodec® are registered trademarks. All trademarks are property of their respective companies. © Copyright 1982-2019 Robert Orban and Greg Ogonowski. Rorb Inc., Belmont CA 94002 USA Modulation Index LLC, 1249 S. Diamond Bar Blvd Suite 314, Diamond Bar, CA 91765-4122 USA Phone: +1 909 860 6760; E-Mail: [email protected]; Site: https://www.indexcom.com Table of Contents TABLE OF CONTENTS ............................................................................................................ 3 MAINTAINING AUDIO QUALITY IN THE BROADCAST/NETCAST FACILITY ..................................... 1 Authors’ Note ....................................................................................................................... 1 Preface ......................................................................................................................... 1 Introduction ................................................................................................................ 2 The “Digital Divide” ................................................................................................... 3 Audio Processing: The Final Polish ............................................................................ 3 PART 1: RECORDING MEDIA ................................................................................................. 5 Compact Disc ............................................................................................................... 5 CD-R and CD-RW, DVD±R, DVD±RW, DVD-A, HD DVD, Blu-ray .............................. 7 HDCD .................................................................................................................................... 8 Digital Tape ................................................................................................................. 9 Hard Disk Systems ..................................................................................................... 10 Flash RAM ................................................................................................................. 10 Program Associated Data (PAD) or Metadata ........................................................ 11 Data Compression ..................................................................................................... 12 Lossless Compression ......................................................................................................... 12 Lossy Compression ............................................................................................................. 13 MPEG1 — Layer 2/3 ............................................................................................................ 15 AAC/HE-AAC ....................................................................................................................... 15 Members of the HE-AAC Codec Family............................................................................. 16 Independent quality evaluations of AAC/HE-AAC ........................................................... 19 Spectral Band Replication .................................................................................................. 19 Parametric Stereo .............................................................................................................. 21 MPEG Surround .................................................................................................................. 21 Using Data Compression for Contribution ....................................................................... 22 Pitfalls When Using Dolby AC3 as a Contribution Codec ................................................ 23 PART 2: SYSTEM CONSIDERATIONS ...................................................................................... 23 Analog Interconnection ........................................................................................... 23 Grounding .......................................................................................................................... 24 AES3 and SP/DIF Digital Interconnection ................................................................ 24 Digital Audio Clock ............................................................................................................ 25 Sample Rate Conversion in Digital Audio Distribution .................................................... 27 Audio over IP ............................................................................................................ 28 MADI.......................................................................................................................... 29 Headroom and Metering ......................................................................................... 30 Peak Normalization in Audio Editing Programs .............................................................. 30 Headroom .......................................................................................................................... 31 Measuring and Controlling Loudness ..................................................................... 35 BS.1770 Loudness Meter .................................................................................................... 35 EBU R128 ............................................................................................................................ 36 ATSC A/85 ........................................................................................................................... 37 Orban Loudness Meter ...................................................................................................... 37 Jones & Torick (CBS Technology Center) Meter ............................................................... 38 Loudness Balance between Speech and Music ................................................................. 38 Replay Gain ........................................................................................................................ 39 Electronic Quality ..................................................................................................... 40 Quality in Digital Chains .......................................................................................... 42 There are several pervasive myths regarding digital audio: ............................................ 45 And finally, some truisms regarding loudness and quality: ............................................. 48 The Nielsen Audio® PPM (Portable People Meter) ............................................... 48 PART 3: CONFIGURING AND USING THE PRODUCTION STUDIO ................................................. 50 Monitor Loudspeakers ............................................................................................. 50 Choosing Monitor Loudspeakers ....................................................................................... 50 Loudspeaker Location and Room Acoustics ...................................................................... 51 Loudspeaker Equalization ................................................................................................. 52 Other Production Equipment .................................................................................. 54 Production Practices ................................................................................................. 55 Quality Control in Transfers to Playout Systems .................................................... 58 Program Material Quality and Authenticity ..................................................................... 58 Vinyl .................................................................................................................................... 61 Mechanics of Transfer ........................................................................................................ 61 Analog Connections ........................................................................................................... 63 Analog Operating Levels ................................................................................................... 63 0 dBFS+ (True-Peak Overloads) .......................................................................................... 63 Figure 2: Sinewave at 0.25 fs sampled at 45 degree points, showing +3 dBFSTP true peak level ............................................................................................................................ 64 Screening Sources for Technical Problems ........................................................................ 65 Sony/BMG Rootkit Malware .............................................................................................. 66 Mono Compatibility ........................................................................................................... 66 Stereo Enhancement .......................................................................................................... 68 Pre-Processing Files in Playout Systems ............................................................................. 69 Restoration Software ............................................................................................... 69 Editing in the Spectral Domain ......................................................................................... 71 Figure 3: Editing the Spectral Domain .............................................................................. 71 De-Clipping