Friday, 5 December 2008

An introduction to low power FM transmission (or pirate radio basics...) part 5

Considerations on Dynamics or Audio File Standards for the Broadcast Industry

Taken from

by Jeff Schroeder

Most broadcasters work hard to present the cleanest audio possible. However, there is one part of the chain – hard to measure with traditional test gear – that can undo your careful effort at quality. To avoid distortion from “stacked algorithms” Jeff Schroeder suggests we get together as an industry and create standards for incoming audio files.

It began when we got the first CD decks in our on-air studios. “Now in full digital quality, it’s Hey Lewis and the News on KIQY-FM!” I remember saying those exact words at least a dozen times in my “other” life on the air. That was 1985. Fast forward to 2006 – and for the most part we still are saying the same thing: “Broadcasting in full digital quality.” Only now a very high percentage – if not all – of the music, commercials, jingles, and liners are actually of a much lower audio quality than that first Hey Lewis CD I played from a Technics consumer CD deck back in 1985. What happened?

I can hear you saying: “but we are playing the files in linear file format from a $3,000 audio card on a $2,000 computer. Yes, you are. But, where did the original files come from? iTunes? New Music Server? Your friend’s iPod? Or did you actually take the time to rip it from the original CD? And what about the commercials that are running on your air now? When was the last time you actually got a commercial on a CD or Tape? The vast majority of – if not all – commercials are now delivered in file form. Have you really ever taken the time to inspect the properties of the audio files coming into your facility? Looked at the sample rate? Bit rate? RMS levels of the audio? Most people have not. The commercial/ song/liner simply comes in the building, gets converted to the automation system file format and uploaded. When I travel around the country I am amazed at some of the audio that I hear on the air – commercials in particular. The sound is so bad that it is often stressful to them.

It is clear to anyone literate in producing clean audio that it is getting harder to find. Far too many of the current CDs are already smashed, crunched, and clipped before they get to you. But then they enter the typical broadcast audio chain where stacked compression algorithms are digital audio’s worst enemy. To illustrate, just look at the typical distribution path used today to get audio on the air:

1. Production happens in full digital multi-track editor and mixed down to a linear wave file.
2. The “send out” copy is made from the file and saved in a minimum “standard” 256 kbps MP3 file (with 5.5:1 compression) to save on upload/download bandwidth (Generation 1)
3. The local production dude (or dudette) downloads the file and opens an editor to put on the local tag. Then he/she saves the file in 128 kbps MP3 format, compressed 11:1. (Generation 2)
4. The file is then sent to the automation system, typically using 4.4:1 compressed MP2. (Generation 3)
5. The file makes it to the air. Audio processors and HD exciters add coding (Generation 4) or (even 5!

Sadly, this is sometimes the best case scenario. Often the process is repeated many times over, creating files that are technically digital audio, but sound so bad they should not be played on a $9 clock radio. At one time or another, we have all been told by the sales manager that we “must play the commercial” that we received from the client because “it’s $(insert dollar figure) per minute – and they pay fast!” Even if the file turns out to be a copy of a 6.3:1 MP2 that a station across town pulled of their automation and emailed to you.

I clearly remember the very loud outcry about the 4.4:1 MP2 compressed audio coming from PD’s when we first started playing music from hard drives on automation computers. This was only 7 to 10 years ago. Oh, how things have changed in this very short time! We as an industry (Radio) are at a true turning point. With more and more stations turning on HD signals and the added compression algorithm involved with HD, there must be something done about the quality of audio files that we will accept and actually play on our radio stations. Our listeners now have a vast selection of digital products from which to choose. We have to sound better than those choices in content and sound. Content is another subject which must be addressed by all the programming guru’s. What I am talking about is the quality of the audio sound. The problem is that currently there are no real standards that would improve this. What is the solution?

We will take the easy one first: Education. It is imperative that the people who are handling the files (Program Directors, Music Directors, Production People, etc.) learn and understand what digital compression is and how it affects the overall quality of the finished product – which is, after all, the on-air sound of your station(s). Your staff does not have to go out and buy their own copy of Audio Files for Dummies. However, if they see a file come into the building that is a 128 kbps MP3, they do need to know enough so that they quickly can identify the file type and “properties” of the file. Then, if necessary, they are able to identify problems and do everything in their power to get that file replaced with a higher quality file. This point is particularly important for music that will go into the library and be there for a long time.

Here is a chart of the compression ratios of MP3 files and the file sizes they generate, compared with a linear file.

You can see that the consumer standard of 128 kbps is at 11.0:1 compression. You can also see that the highest quality bit-rate of any MP3 file is still running 4.4:1 compression. A good visual example comes from a current country song on the charts today. A very simple comparison of the frequency spectrum before and after a file is pulled from a CD will be instructive. This is something every one of your production and air people should be able to grasp in an instant.

Comparing native CD audio to an MP3 dub.

The solid lines at the top reflect the frequency response of the original WAV file ripped directly from the CD. The solid filled-in (blue) part is the exact same section of the song after converting it to 192 kbps MP3. You can see the dramatic and absolute roll-off at 16 kHz. This happens with every file converted to MP3 on the very first generation – it is “by design.” This is just the most graphic example of what happens to an audio file being compressed; there are other, more harmful artifacts that happen, but that is something for a future discussion. You cannot reduce the size of an audio file without removing little “pieces” of the audio itself. These pieces can never be replaced and if the file is compressed more than once the audible quality denigration becomes almost exponential.

Now, I am a realist. I understand that music now is being sent out on “release day” in compressed file format. In a competitive environment, stations have to play some songs the second they enter the building – and sometimes the only way they can get that file “right now” is downloading a compressed file. The solution: yes – use it. But then replace it as soon as you can get your hands on a CD or linear copy of the song. Never archive original audio in MP3 format! Yet, I see this all the time, all over the country. For any audio that has a chance of making it back on the air from an archive, all work should be done and saved in full linear uncompressed file format. Hard drives are cheap now. Again: archive all original audio in linear wave format. Indeed, why archive bad audio for future use? Too many times an element gets put into the automation system with the best intentions of eventually replacing it. Yet, if you were to go back into the system a couple of years later, the file likely would still be there largely because it does not sound so bad next to all of the other bad files.

Another area of education deals with understanding the on-Line download “stores” such as iTunes. Not even taking into account the legality of downloading a song for “personal use” and playing it on the air, the files are compressed – sometimes highly compressed – and that compression will live on forever with that original source file. Please understand, I am not saying not to use all legally available means to get a song or file that you cannot get anywhere else. But if this is going to remain in your library, replace it with a high quality linear wave file as soon as possible.Unfortunately, as bad as such artifacts are now, HD will only make it worse. A badly compressed file will only be amplified by the compression algorithm of HD. It really is “Garbage in, Really Bad Stinky Rotten Garbage Out.” (I am not very opinionated, am I?)

Now the more difficult issue: Standards. I am of the opinion that we – as an industry – can and should set the bar for what we are going to accept into our buildings from a file format standard. The problems: What should that standard be? Who should set the standard? And of the most importance, who is going to enforce the standard?

As you might guess from the tone of this article, a lot of us at Citadel Broadcasting have been seriously discussing this topic at length, But it really does come down to cooperation from the entire industry. If we (Citadel) set a standard for music that we are going to accept and the competition across the street does not have the same standard, are we going to forgo being first with a “Debut” song from a core artist because the file is below our standards? Of course not. That is just not going to happen. I know it, you know it. But there goes the standard! The only way any standard is going to work is if we (Radio) set the bar and tell all of the music labels, production houses, and any other providers what our standards are – and stick by those agreed upon standards. I have had informal discussions with some of the second hand providers already, and for the most part they are as frustrated as we are. They are simply not receiving high quality linear files from the record labels on a consistent basis – and when they do they are limited by drive space and bandwidth just as we are. So, how do we begin? I would be willing to get together with any company, provider, or record label that would be willing to open the subject and possibly come up with some “base-line” standards that we could – over time – implement and eventually get the providers to adhere to. Is this possible? Is this something that we as an industry can get together on and put the power of numbers on our side? I am willing to try. Are you?

Jeff Schroeder is the Corporate Director of Digital Technology for Citadel Broadcasting Company. If you feel strongly about today’s broadcast audioquality, contact Jeff at jeff.schroeder (at)

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