Scope
To understand Linear Acoustic TV audio processing, or any TV audio processing, it is necessary to understand the legislative requirements and how and where the processors fit into the TV broadcast chain. This document introduces the TV broadcast signal chain, and Linear Acoustic audio processing for television.
Setting the Stage for Modern TV Audio
TV Audio Processing: Loudness Control
Around the world, complaints about loud commercials came from viewers soon after broadcasters transitioned from analog (NTSC in North America) to digital television delivery (ATSC1 globally). Loud commercials became enough of a priority for the public that the Federal Communications Commission (FCC) enacted rules that require commercials to have the same average volume as the programs they accompany. Similar regulations now apply in many (most?) nations of the world.
Digital TV broadcasting does not have audio limitations similar to the modulation limits of FM broadcasting used for analog radio and TV audio. The ability to use, misuse, or ignore audio processing resulted in the delivery of content with LARGE volume differences. This quickly made TV commercials more annoying, then they were in analog broadcasting. Whether done deliberately or through a misunderstanding of the medium itself, it required legislation to control the loudness of commercials in the context of the programs that the advertising appeared within.
To better understand TV audio loudness regulations and how they relate to TV audio processing, see the article:
https://docs.telosalliance.com/docs/tv-audio-loudness-and-digital-tv-broadcasting
TV Audio Processing: The Need for Real-Time Processing
Typical over-the-air TV broadcasters deliver a wide variety of content from an even wider variety of sources. Consider that local TV stations broadcast: their own studio news programs, live remote news segments, prerecorded program content, promotional content, public service programs, and voiceovers. Then there is network news, longform news programs, entertainment programs, sports, network promos, and advertisements produced in the local market, and from national sources. Do not forget syndicated programs and movies that can include content produced from the 1940’s through the current year.
The case for delivery of content from TV networks adds more variables. There are all kinds of live broadcasts (news, sports, weather, special events, etc). Then there is content, whether programs, advertisements, promotional material, or pre-recorded, that is available in advance and may have audio processing done in advance using file-based, non-real-time methods. This requires a careful blend of real-time and off-line audio processing.
Much of TV advertising content for stations and networks is delivered just in time for broadcast. Many networks have vast libraries of content and believe that the effort to process all of it for broadcast is not economically feasible. And, perhaps the most important reason of all, is that content is delivered to broadcasters providing the last mile globally. The consequence of all these different delivery scenarios is that broadcast stations and networks will both have real-time audio processing in their air chains. In al cases it helps ensure that a consistent audio level is delivered to all of the distributors and local stations, which then do final audio processing for their particular end users.
Then there are OTT providers (examples are Netflix, HBO MAX, Apple TV, etc) who send content directly to end users. California is the first State in the U.S. to issue legislated requirements for audio level control of OTT content by broadcast entities. Will OTT providers that are delivering content within California create special versions for California only? No, this is too costly and complicated. Instead, it is very likely that ALL OTT content providers, will now have to do audio level control on ALL content. All providers will now have to put audio level control in place for everything they broadcast so they do not have to worry about what may end up OTT in California. This audio control may be real-time or file-based.
TV Audio Processing: A Little History
Since the 1930s, TV stations have put an audio limiter in the air chain. This was to ensure that the audio modulation limits that protected both frequency adjacent TV stations and a station’s own video signal from interference were not exceeded. Beginning in the 1950s some stations added audio AGC that both maintained audio levels above the noise and helped keep audio from constantly hitting the limiters and sounding distorted. By the late 1970s, more sophisticated audio processors became available and TV broadcasters began to hear the advantages of audio processing for TV. Better signal-to-noise ratio for viewers, more consistent audio levels, and even more consistent audio quality across content from different sources and of different ages could be heard. For the next 30 years, audio, video and broadcast technologies all became increasingly sophisticated.
One of the things that happened was that TV advertisers started to use audio processing to make their commercials louder. Advertisers loved it. Home viewers, not so much. However, even with what we can all recognize as radio production methods being used on TV commercials, the audio AGC and limiting, required to maintain mandated modulation limits, meant that TV commercials were not that much louder than program audio.
Around 2001, Tim Carroll, then working for Dolby, realized what was going to happen when TV moved to digital broadcasting. The increased dynamic range, low noise floor and very low distortion were going to reveal the wide variation in audio quality across TV content. Tim wants Dolby to make a digital audio processor for TV. However, Dolby is already getting out of hardware manufacturing to become a software-only company. They say no to making a hardware processor. Tim leaves Dolby to found Linear Acoustic and make a digital audio processor for TV. (The name Linear Acoustic is, AFAIK, a sort of private joke. Human hearing, acoustics, and audio processing are all far from linear in their behavior, and that is the joke.) The audio quality and consistency made possible by Linear Acoustic audio processing got the attention of many TV broadcasters. Linear Acoustic began to compete with existing TV audio processors in North America.
In 2008, Linear Acoustic became part of the Telos Alliance. In 2009 ATSC1, a digital broadcast standard, became mandatory in the U.S. The Linear Acoustic AERO processor was a digital processor and had audio specifications to match ATSC1 audio capabilities. It also had already integrated upmixing to 5.1 audio, downmixing to stereo, Dolby Digital encoding and decoding, Nielsen encoding, and more. It is selling quite well.
At the end of 2012 the FCC put the CALM Act into effect. Every U.S. TV broadcast station must comply with it. Sales of Linear Acoustic processors explode. By 2017, Linear Acoustic’s U.S. resellers estimated that 8 out of 10 U.S. TV stations are using Linear Acoustic processing. Canada and Mexico have also adopted the U.S. FCC CALM Act regulations. Globally, regulations controlling TV audio loudness are being adopted.
Between 2012 and today, Linear Acoustic processors have released updates to the AERO line of processors and added the NGA processors to the product line. New upmixers, watermark encoders, wideband LKFS processors and Dolby encoders have been added.
That brings us to today. Linear Acoustic processors have not been as popular outside of North America as they have been in North America. There are a few reasons for this. One is that Linear Acoustic processors have always been marketed and represented as the best TV processors in the world. The price has always matched the claim. In most of the world TV broadcasting has always been a state controlled media. There are few places outside of North America where broadcasters compete for viewers like they do in the U.S.. State owned broadcasters do not have the steady income to be able to afford to keep up with technical advancements. Purchasing the best technologies does not translate to increased revenue..
There is also a philosophical difference in the way broadcasters approach TV audio processing. (My own belief, from personal experience, is that the philosophy has been heavily influenced by business interests. But that is for another time.) One approach is to deliver the best sound possible for all content. The other approach is to deliver to the audience exactly what the broadcaster is given. Following loudness regulations aside, do not change the timbre, noise, level issues, etc.
In Europe, in particular, many broadcasters regard their contract with a program provider to mean that the program delivered to them will be broadcast EXACTLY as it is delivered. There are many places in the world where the broadcaster does not have any control over the transmission of their content. Our client may be a transmission company who does not want to change the audio of the station broadcaster’s content.
Junger’s Level Magic audio processor was designed to be, and continues to be marketed as, a “transparent” audio loudness controller. Prior to Junger’s reorganization and Telos Alliance becoming their sales force, Junger was our biggest competitor. The Linear Acoustic NGA processor, the LA 5300 offers the transparent Apto loudness control. There are no audio processing elements except loudness control.
This variety of content requires an enormous range of audio processing capabilities. This is something that Linear Acoustic AERO processors have excelled at since the first Octimax digital audio processor, released around 2002.
Linear Acoustic Processors: Basic Features
Linear Acoustic AERO-based processors offer comprehensive audio control elements: wideband input AGC, multiple wideband and narrowband AGCs, multiband downward expansion (sometimes called noise reduction), parametric EQ, multiband compression (2 to 7 bands), multiband limiting, wideband TruePeak limiting, and wideband, time windowed, LKFS level control.
In addition to the above-mentioned processing types, Linear Acoustic AERO processors offer a range of processing configurations to meet the needs of broadcasters:
• AMX5.1: Auto upmix + 5.1 + 2.0 + 2.0
• AMX2.0: Auto downmix + 2.0 + 2.0 + 2.0
• AMC5×2 2.0 + 2.0 + 2.0 + 2.0 + 2.0
The new NGA processor, the LA5300, offers management of immersive formats as well as stereo and 5.1 audio.
• Fixed and automatic upmixing of mono to dual mono
• stereo to 5.1, 5.1.4, and 5.1 to 5.1.4, 7.1 and 7.1.4.
• Downmixing of 5.1, 5.1.4, 7.1 and 7.1.4 to stereo.
• Encode and decode of Dolby Digital, Dolby Digital Plus, Dolby AC-4
• Special versions offer Dolby AC4 mezzanine formats.
• Nielsen, Kantar and Verance watermarking.
The new LA5291 offers transcoding between advanced Dolby codecs.
• Decoding from Dolby ED2 to PCM
• Transcoding from Dolby ED2 and Dolby E to Dolby Digital Plus and Dolby Digital Plus JOC
• Encoding PCM to Dolby Digital Plus, Dolby Digital Plus JOC, and Dolby ED2
There are also a wide variety of miscellaneous features and functions in the AERO processors and LA5300, including:
• Insertion of EAS and local emergency audio triggered by audio presence and/or GPI
• Automatic selection of audio description vs EAS based on audio presence or GPI
• Network and local audio insertion
• Ability to save an unlimited number of audio presets
• Selection of audio presets based on an internal day of week and hour of day schedule or via GPI (AERO)
• External ASCII commands to execute any AERO parameter change. (AERO)
• An internal scripting capability that can be associated with the internal scheduler and/or external commands and GPI. (AERO)
• Embedding and re-embedding audio in SDI
• Up to 5 x AES-3 I/O
• Deriving sync from SDI source, VTC, or AES3 lock for embedding and de-embedding.
• Dual sync for audio embedding and de-embedding from SDI video and PTP clock for AES67/SMPTE 2110-30/31 I/O.
Bear in mind that not all Linear Acoustic processors are capable of all of the above. Each processor has its own set of capabilities. Solving a client’s problem requires knowledge of what each processor is capable of and choosing the right product to fit the client’s needs and budget.