author is a senior operations engineer for Clear Channel Media +
Entertainment’s Engineering and Systems Integration Group. He holds
several SBE certifications including CSRE, CBNE, AMD and DRB. His
opinions are not necessarily those of Clear Channel or Radio World.
1: OEM Automotive Radio: GMC Terrain
2: OEM Automotive Radio: Toyota/Lexus
the United States, many broadcasters have employed HD Radio as a
method to provide digital transmission alongside analog transmission
on the FM and AM bands. While the initial focus of many broadcasters
implementing HD Radio was to provide digital audio delivery to
consumers, some of the emphasis on this has changed in recent years.
The HD Radio transmission system is flexible enough to use portions
of the digital spectrum for data instead of audio.
of the emphasis for data delivery via HD Radio has been on the FM
bands, as the data rate starts at 96 kilobits per second (kbps) in
standard MP1 hybrid mode. The audio channels on HD Radio use
adjustable-bitrate codecs, so the bitrate of the audio channel(s) can
be reduced slightly to allow for additional data services. The total
available bandwidth increases from 96 kbps to 124 kbps in MP3 mode,
149 kbps in extended hybrid MP11 mode, and 253 kbps in all digital
MP6 + MS4 mode.
this time, the AM HD Radio system does not offer the framework to
provide these services, as all the data must be used for the audio
codec. There is also considerably less bandwidth to allocate for this
process, which would decrease audio quality. MA1 Core Only mode
offers 20 kbps, MA1 Full Hybrid mode offers almost 37 kbps, and MA3
All Digital mode offers nearly 40 kbps.
ARTIST EXPERIENCE DEFINED
services delivered over HD Radio are an exciting and growing
development in the industry. One of the most visible applications of
data delivery is the concept of using some of the data bandwidth
available in the HD Radio stream to deliver graphical images
synchronized with the audio. This involves sending images related to
the current song on the air, such as album cover art. The concept is
known as Artist Experience. The concept dates back to the earliest
inception of Advanced Application Services over HD Radio technology
Channel Media and Entertainment worked with iBiquity on the initial
commercial efforts of this service and started the first
implementations of Artist Experience in June 2010. The two companies
worked together to provide a proof of concept and an initial
development of this new feature. The result of that effort included
an implementation offered by iBiquity to all broadcasters, which
became available in May 2011.
Artist Experience was evolving, Clear Channel’s initial rollout
took some time and was only offered on a limited number of stations
so that development could be focused. Much planning was needed to
develop an internal solution for providing album art to many stations
concurrently. The design needed to consider approximately 390 HD
Radio stations running Artist Experience, which when coupled with HD2
formats meant that the system had to simultaneously support
approximately 780 individual audio channels. It also needed to be
scalable for any additional stations we decide to convert to HD Radio
in the future. To date, there are no products on the market that
scale to this level.
3: OEM Automotive Radio: Volkswagen
4: Aftermarket JVC (upper) and Kenwood (lower)
Channel completed its nationwide rollout of Artist Experience in
September 2012. This process has not gone without challenges. We have
learned quite a bit in the process and continue to refine our
implementation. It is our hope to share this information with the
industry to help assist other broadcasters and vendors in this
endeavor, as we feel this is a good development for the industry.
with Artist Experience support are being released to the marketplace
in various forms, including but not limited to portable, tabletop,
aftermarket automotive and OEM automotive (factory-installed car
radios). A list of some of the products available for purchase that
support this technology are in Table 1, and some Artist Experience
images from these receivers are shown in Figs. 1–5.
number of receivers supporting Artist Experience continues to grow,
and there is interest from automotive manufacturers in implementing
this feature. BMW, Buick, Chevrolet, GMC, Lexus, Mazda, Toyota and
Volkswagen have radios in some of their models that support it. More
designs from these manufacturers and others are on their way.
There are multiple
factors driving this. Consumers are used to smartphone devices with
interactivity and apps — and the automotive space is starting to
embrace this trend. In addition, the United States Department of
Transportation is mandating backup cameras in all vehicles produced
after May 1, 2018. Most implementations require an LCD screen in the
“center stack” of the dashboard — where the radio typically is.
Automotive companies are looking to use this screen in ways to
produce a positive experience for the driver and passengers when the
car is not in reverse. Artist Experience is one of the items many
automotive manufacturers are implementing — it is free content for
them — and this is certainly an exciting feature that radio
stations can offer to their listeners.
Experience offers a great listener benefit. It also gives terrestrial
radio a visual element to help compete with so many other digital
audio products, such as portable audio players, streaming websites
and smartphone apps.
TIMING AND DISPLAY CONSIDERATIONS
image displayed must be tightly synchronized with the song or audio
being played. Only one image can be associated with an individual
song. If the Cover Art or primary image is unavailable, a station
logo or other default image is displayed on the receiver. Fig. 5
shows an example of a station logo.
Service Data (PSD), formerly known as Program-Associated Data (PAD),
is a structured data format that provides metadata (title, artist,
album and other information about the song) currently on the air. PSD
messages must arrive at the broadcast equipment within 0.5s of each
new segment or song, so that the image can be tightly synchronized
with the song.
5: Insignia Tabletop and Portable
image synchronization trigger is sent through a custom frame in PSD
called the XHDR. The image should be sent prior to the start of the
associated song. Transmitting station logos is critical since
receivers use the logos as a fallback when song specific synchronized
images are unavailable.
BROADCAST SYSTEM REQUIREMENTS
emphasis in this paper is to help broadcasters implement Artist
Experience on their stations. To do that, one needs to understand the
overall system architecture and the requirements in greater detail.
the station must be an FM station transmitting an HD Radio signal.
That is an entire topic in itself, but it requires a transmitter and
exciter capable of generating the digital IBOC waveforms. The exciter
has an Exgine card, which is an Ethernet interface that accepts HD
Radio encoded information from the Exporter. This link is considered
the Exporter to Exciter (E2X) link. The Exporter should be running
IRSS 4.3.2 or greater. Clear Channel recommends and uses version
4.4.7 on all of its stations, which is the latest available at the
time of this writing. Exporters running versions below 4.3.2 will
need to be upgraded; consult your equipment manufacturer for
you are planning an upgrade, be sure to use 4.4.7. While 4.4.7 is not
required to deploy Artist Experience, it adds a few new features. And
most important, it adds to the robustness and stability of your HD
Radio systems. Note, Exporter and Exciter hardware combinations that
predate the Exgine configuration platform use Low Voltage
Differential Signaling (LVDS). These systems can also support Artist
Experience if using the proper software versions.
Exporter encodes the Main Program Service (MPS) HD1 audio, along with
any data that comes from an Importer. Typically, the Importer was
just used for encoding your Secondary Program Service 1 (SPS1) HD2,
SPS2/HD3, etc. audio channels. However, it is also where any
ancillary data sent via your HD Radio signal is put together and
transmitted to the Exporter. This data is aggregated by the Importer
and then transmitted through the Importer to Exporter (I2E) link.
Since Artist Experience is an additional data stream, it is encoded
on the Importer as well.
Importer, too, should be running version 4.4.7. While 4.3.1P1 may
work, we strongly recommend 4.4.7 in combination with Exporter 4.4.7.
This pairing makes the I2E link very robust. It also includes a newer
version of the SPS Capture Client which encodes the SPS (HD2, HD3,
etc.) audio that is much more robust and stable than previous
versions. The Importer must be configured to allocate a portion of
the HD Radio data bandwidth for Artist Experience. This is typically
4 kilobytes per second.
engineers and IT technicians who have implemented HD Radio systems
before are familiar with these components we have just discussed. The
biggest change — and how Artist Experience is implemented — is a
program called MSAC that runs on the Importer.
MULTIPORT SYNCHRONOUS/ASYNCHRONOUS CLIENT (MSAC)
is a platform-independent software program written in Java and
designed by iBiquity, used to send data over the HD Radio
transmission system. It can be configured in a variety of ways
depending on the data transmission requirements. In the case of album
art, it is used in a Large Object Transfer (LOT) capacity to transmit
images at specific times to receivers.
MSAC client software is distributed by the Importer manufacturer and
the license is conveyed as part of the Importer license. Station
usage of MSAC falls under the standard terms of the advanced services
license with iBiquity.
accepts incoming TCP or UDP messages from a data provider. For Artist
Experience, TCP/UDP messages must be sent from the server,
application or device that is providing your album art. This
information is transmitted to MSAC via a structured data format
provided by iBiquity when a developer makes arrangements to obtain
the MSAC API/SDK. Once received, the images are scheduled to be
transferred via the HD Radio transmission system.
the case of Artist Experience, there are two types of requests that
are sent to MSAC, pre-sync and sync events. And for station logo,
there are async events. These events associate images for
transmission via the HD Radio data system.
the image to be shown successfully at the start of the song, the
image must be transferred to the receiver before the song occurs.
That is because there are inherent delays in the HD Radio
transmission system as information is buffered, transmitted and
decoded. In addition to those encoding delays, there are transmission
delays in the album art data channel itself.
art images are in the JPG or PNG format, sized to 200 x 200 pixels,
and have a maximum file size of 24 kilobytes. Generally, the data
size allocated for transmission of Artist Experience is 4 kbps. So, a
maximum file size image of 24 kilobytes would take 48 seconds to
transmit. Smaller files obviously would take less time to transmit.
6: Clear Channel Artist Experience System Topology
Artist Experience bandwidth is pooled across all HD channels, so the
images for the MPS/HD1, SPS1/HD2 and other channels share the same
data bandwidth. Since it takes time to transmit files through the
data channel, there is possible contention between multiple HD audio
channels (two songs may start at approximately the same time).
must schedule sending the image before the song starts depending on
the bandwidth allocated, the size of the image and considering when
images may need to be transmitted for other audio channels. MSAC is
dynamic and does these calculations on the fly. It is configurable
and will optimize to make use of the available bandwidth based on the
following factors: size of the image, the image repeat rate and the
image data transfer rate.
key to making sure those images arrive at the radio before the song
starts is to have MSAC properly configured, have your time synced to
a reliable source for all systems (automation, any middleware,
Importer) and have your systems accurately predict when the next song
is going to play. Timing is very important, and if the system time of
any of these components departs from exact time, this could cause
issues in transmitting images. It is important for solutions to
consider any non-HD related delays in the transmission system in its
timing calculations. Most commonly, this would be the use of
profanity delays on the radio station. Commands being sent to the
MSAC must be compensated for any non-HD related delays, such as a
best way to make sure images are sent at the proper time is to ensure
the on-air playback automation system is set to export the current
song playing plus at least one (or more) of the songs next to play to
your album art services. These systems can then forward the estimated
time the next song will play to MSAC. When MSAC has this information,
it can make sure images are delivered once to receivers shortly
before each song starts.
1. Select Receivers With Artist Experience
if the timing calculations are correct from the automation feeds the
item will be received by a receiver about 10 seconds before the song
starts. The receiver stores the image and prepares it for display.
TRIGGERS AND SYNC EVENTS
the song starts to play, your Artist Experience solution needs to do
two things concurrently.
a Program Service Data (PSD) message needs to be sent to the Exporter
(MPS/HD1) or Importer SPS Capture Client (SPS1/HD2, SPS2/HD3, etc.).
This is likely already happening in your older system so that radios
could show the PSD (title, artist, album etc.) of the current song in
text form on the receiver display.
to implement Artist Experience, your systems must incorporate HD
Radio HDP PSD SDK v4.7 or greater. These versions support an image
synchronization trigger through a custom frame in the PSD called the
XHDR. This trigger matches an image previously sent by MSAC through a
unique identifier called a LOT ID. Without the PSD message with the
XHDR trigger, the image would simply sit in the receiver memory but
never be displayed. The PSD trigger is what indicates to the receiver
that the image is associated with this song. As mentioned previously,
the PSD message timing must also be compensate for any non-HD
transmission delays, such as a profanity delay, to make sure the PSD
(title/artist) data and the image are displayed when the song starts
second item that needs to happen concurrently with a new song
starting is that your systems need to send a SYNC event to MSAC to
let it know that the song has started playing. This allows MSAC to
schedule a send of the image shortly after the song start. For
receivers that were tuned in before the song started, this is a
redundant send and ignored. For those receivers that were not tuned
into the station before, or had a data impairment issue at time of
transmission, they will receive the image shortly after the song
starts. Remember, the sync event should also compensate for profanity
or other delays.
SYNC event also allows MSAC to know if the timing of the song start
has changed. This could happen if the song was started early for some
reason, i.e. maybe the on-air operator started it earlier than
scheduled, or quickly juggled around the schedule. The SYNC event
keeps MSAC up-to-date with the song timing information so that it can
continue to optimize the transmission of images to receivers.
Depending on the configuration of the MSAC, it is possible for MSAC
to send the image a third or more times after the song has started.
However to conserve bandwidth, it is typically recommended to only
send it once more, perhaps no later than halfway through the song.
STATION LOGO MSAC REQUESTS AND PSD TRIGGERS
transmit a station logo, there are a few things to consider. The logo
image must follow the same technical specifications (JPEG or PNG,
200x200, under 24 kilobytes). MSAC must be told about the station
logo via a slightly different message called an ASYNC SEND request.
This request needs to be sent periodically so that MSAC is aware of
the logo associated with the specific channel (HD1/MPS, HD2/SPS1,
HD3/SPS2, etc.). Once the request has been received by MSAC, it will
schedule the station logo to be sent periodically. While
configurable, Station Logo tends to be broadcast once every 15
minutes or less. MSAC treats this as a low-priority send.
MSAC sends the station logo, receivers that support this service will
cache the logo. It can be displayed in instances where no Artist
Experience image was sent for a particular song. It can also be
displayed when the broadcaster sends a specially crafted PSD XHDR
message to the receiver indicating that the station logo should be
displayed. For instance, at Clear Channel, we use this command when
we display the default generic PSD messages, so that receivers that
support Station Logo will display the image.
should be noted that not all radios that support Artist Experience
support Station Logo. While Station Logo is supported in the majority
of receivers, the decision to implement this feature is left with the
receiver manufacturer. They may leave it out to control cost or
conserve available memory space. On these types of radios, they may
display a generic image for all stations, such as the HD Radio logo,
or perhaps a generic music note or other image.
RECEIVER IMAGE CACHING AND STORAGE
item left to the receiver manufacturer is how to store or cache
images. Some advanced designs cache these images to non-volatile
storage devices such as flash memory or a hard drive. These tend to
be some of the best implementations, because the radio will associate
and store the image for a particular station, song, title, artist and
its unique LOT ID. For these receivers, you can tune into the station
and receive an image once and the radio will remember that image for
that song. If you tune away to another station and then tune back to
the original station, the image will display immediately. Or, you
could tune into that station hours or days later and in the middle of
the song and the receiver can display the image immediately.
contrast, other receivers only store the images in volatile memory,
which means that it only stores the images temporarily. There are
some that save them per radio listening session, so they will act
like the radios with more permanent storage methods, but when the
receiver is powered off, it loses these images.
at lower price points limit memory, as it is a considerable cost
factor. There may only be enough memory to store the image for the
current song and the next song. If you tune away from a station in
the middle of the song, and then tune back, it may purge the images
in memory. Then you will have to wait until MSAC transmits the image
again before it will display to the consumer.
same storage and memory considerations apply to the Station Logo
service as well. You may notice certain receivers permanently storing
station logo images, while others might need to wait until that is
sent over the HD Radio system by MSAC before displaying it each time
you tune to the station.
ALBUM ART SOURCES AND MATCHING
consideration in implementing Artist Experience is licensing the use
of album cover art or other images for transmission. Clear Channel
directly negotiates with providers of these images for our many
distribution platforms (iHeartRadio streaming, web/digital, mobile,
etc.) so we were able to include HD Radio as part of our licensing
of the largest challenges in this process has been trying to include
relevant artwork for all of the songs that our stations play across
the country. Clear Channel employs a centralized database of all
songs, which is managed and maintained uniformly throughout the
enterprise. This offers us great benefits, in that everything related
to the songs we play can be managed, including extended song metadata
from a single source. Clear Channel catalogs more than just artist
and title, but many other relevant fields, such as iTunes reference
data and album art image data. We are constantly striving to improve
the match rate of songs and album art. However, it is a continual
process to maintain that library.
ARTIST EXPERIENCE SOLUTIONS PROVIDERS
of this paper has focused on the early development and concepts
behind Artist Experience from Clear Channel’s implementation
perspective. These components are summarized in Fig. 6. While the
scale of the system we have developed is extensive, such scope is not
necessarily needed for individual stations or small- to medium-sized
group owners to employ Artist Experience on their stations.
are several third-party software/hardware companies that provide
solutions. While neither I nor Clear Channel endorses any particular
vendor named below, these companies have partnerships with iBiquity
and automation system vendors to provide Artist Experience for your
of which solution you select, the concepts mentioned above apply to
whether your company develops its own Artist Experience system like
Clear Channel did, or decides to select an outside product. The
providers below offer middleware software/hardware solutions that can
be placed between your on-air playback automation system, and the HD
Radio software/hardware infrastructure designed by iBiquity.
solutions collect the now playing and future playing song information
from the station’s on-air playback automation systems, match them
with album art or other relevant images, and send them to the
Importer and MSAC for transmission.
of these vendors offers matching of songs to cover art, and can
assist you in matching, monitoring, maintaining and licensing those
images for transmission:
Palm’s Center Stage
Live CS RDS
“The Radio Experience”
Interactive / TagStation
STANDARDIZATION AND SCALABILITY
is the main reason why Clear Channel was able to implement this
feature so rapidly nationwide. Once the final parameters of deploying
Artist Experience were determined, we were able to convert the
initial batch of approximately 80 stations in a matter of weeks to
our new systems. We learned from that process, and used those
experiences to help roll out the remaining 310 stations in a period
of three months. The final push of 170 stations was completed in a
two-week timeframe. Our standardization process was so refined that
an individual engineer at the market level would spend approximately
an hour onboarding their first station, and then typically 30 minutes
or less implementing additional stations.
those charged with implementing Artist Experience on more than a
handful of stations, I strongly recommend that standardization be
considered as part of your Artist Experience deployment strategy.
There are many components needed to execute this properly and it is
best to consider standardizing to implement this rapidly.
recommend that you standardize your Exporter version to version
4.4.7. Make sure every station is running the same version of
Exporter. Having a variety of versions may cause you slight
variations or differences in your rollout.
I recommend that you standardize your Importer version and
configuration to version 4.4.7. Much of the legwork to get Artist
Experience working involves configuring the Importer. It seems many
engineers deal with importers on a one-by-one basis. If you have only
a few stations, that might be fine. But upgrading importers,
reinstalling software and other aspects can be cumbersome and not
easily duplicated amongst several Importers. If you have more than a
few stations, you should consider putting your IT skills to work and
develop a standardized image (OS included) for the Importer.
Hopefully you do not have too many hardware variations to consider as
part of this. It does help in cases where you have a large variety of
types of Importer hardware to consider standardizing on a single
hardware platform. That makes this process much simpler to implement.
Also in cases of a hardware failure, it is much easier to restore the
station back to full functionality. If you do go in this direction,
start with a freshly formatted hard drive, a new OS installation, new
installation of Importer 4.4.7 and latest MSAC. Have all of your
configurations complete before creating your system image.
making images of the entire Importer is not something you wish to do,
I do encourage making backups of the Importer and MSAC configurations
from an Importer where you have everything working to your
satisfaction. You can restore these configurations on other
Importers, but you will also have to closely monitor version
differences on the Importer software and MSAC. The amount of time you
spend upgrading Importer versions and restoring configurations can be
extensive. This is why I recommend developing a full image for the
Importer already installed and configured the way you want it.
I cannot offer advice of which vendor to select, I recommend you work
with one you have experience with, ask colleagues what solutions they
have used and consider evaluating several products. Once you’ve
made a selection, standardize on this solution for all of your
a few stations working with standardization in mind, and learn from
those implementations. This will make your deployment go so much
faster and save you considerable time, resources, and frustration.
sure you invest in a receiver that supports album art. At this point,
I would recommend using one of the aftermarket automotive radios.
Personally, I have used the JVC devices the most, and their Album Art
implementations are very good. While they are expensive, you can
either install them in a car as designed or in a fixed location with
a good antenna. The portable units on the market are not as sensitive
or robust. I would not encourage you to make decisions on timing,
delays, and derive an overall impression of Artist Experience from
these devices. Hopefully that experience will improve in the near
thanks to Jeff Detweiler and colleagues at iBiquity Digital Corp. for
providing additional details on Artist Experience to help further the
education and understanding of this technology.
on this or any story. Write to firstname.lastname@example.org.