Audio File Standards for the
article republished from Radio-guide.com April 2007 Issue, Page #24.
Audio File Standards for the
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.
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
quality than that first Hey Lewis CD I played from a Technics consumer CD deck back in
1985. What happened?
PAUSE FOR A WORD ABOUT AUDIO QUALITY
can hear you saying: “but
we are playing the files in linear file format from a $3,000 audio card on a $2,000
you are. But, where
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
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.
QUALITY IS SUFFERING
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
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
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
The file is then sent to the automation system, typically using 4.4:1 compressed MP2. (Generation
The file makes it to the air. Audio processors and HD exciters add coding (Generation
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.
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
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.
problem is that currently there are no real standards that would improve this. What is the
will take the easy one first: Education.
is imperative that the people who are handling the files (Program Directors, Music
Directors, Production People, etc.) learn and understand
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.
THE HOOD ON MP3 FILES
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
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.
native CD audio to an MP3 dub.
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
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.
WITH THE URGENT NEEDS
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
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.
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.
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
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?)
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
going to enforce
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
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
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?
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)