Internet Radio or Streaming Audio: An Introduction

January 22, 2011

Internet radio is a great resource, as it offers the possibility of accessing almost the entire range of recorded music. However, a potential obstacle for the would-be listener is that it comes in such a variety of shapes and sizes that this can become confusing. This article sorts through some of the different types of online audio, suggests how to connect to it; and offers some streaming audio sites to explore.

Codecs and Bit Rates

Typically, two concepts are used to characterize an audio stream, its bit rate and its encoding method (codec). To provide a baseline, consider the bit rate for an audio CD. CD audio delivers 1,411 kilobits of audio data per second (kbps). (It is encoded at a sampling rate of 44,100 samples per second, using 16 bits per sample, and it includes 2 channels. 44,100 x 16 x 2 = 1,411,200). By comparison, most of the streaming audio that you find on the internet is in the 128 to 192 kbps range. This order of magnitude difference in bit rates is the result of how the music is encoded. CD audio consists of uncompressed audio, but streaming audio has been compressed, meaning the original information has been encoded into a smaller amount of data. In order to achieve an audio file that is so much smaller than the original, the encoding methods tend to be lossy, that is, data has been dropped from the file which cannot be recovered. The fidelity of the resulting audio depends on how much data has been dropped and how cleverly the choices have been made about what to leave in and what to leave out. (For a more technical discussion of audio file formats, this wikipedia article is a good place to start.)

The best known form of audio compression (and perhaps still the most common) is the MP3 file. It is often used in audio streaming. Other types of compression include AAC (Advanced Audio Coding), WMA (Microsoft's Windows Media Audio), and Ogg Vorbis (an open standard codec). RealAudio was a pioneer in the area of streamable content, but they seem to have fallen out of favor, lately. However, you occasionally may still run into their proprietary encoding.

For completeness, I should mention that there are lossless compression codecs, as well. Although a lossless compressed file is smaller and holds fewer data bits than the original file, the original information (i.e., the original waveform) can be completely recovered. Lossless codecs can only compress files down to about 60% of their original size; so, you are unlikely to find these being used to stream content over the internet. However, they are very suitable for archiving music on a computer's hard drive, for example, or for providing hi-fidelity files to be downloaded and saved. FLAC (Free Lossless Audio Compression) and Microsoft's lossless WMA are two commonly used lossless audio formats.

Quality of Compressed Audio

Bit rates and codecs give us a way to define and classify audio streams. An audio stream's bit rate provides an empirical measure of how much data is being streamed, for example, but the amount of useful information that can be derived from this data is what matters, and this depends, in turn, on how efficiently the information has been encoded. Since different codecs vary with regard to how efficiently the information is encoded, some codecs will sound better than others at the same bit rate. These differences become more significant and noticeable as an audio stream's bit rate becomes smaller (e.g., 128 kbps and less).

The practical question of how much audio quality is good enough for your listening enjoyment is complicated by contextual and subjective factors. For example, how acute an individual's hearing is, what sort of equipment is being used to play the music, the environment in which the music is being listened to, and even one's personal taste in sound will all have an important role to play when judging the quality of the audio that is being listened to. With so many different factors in play, it really is not practical to state that certain bit rates and codecs provide particular levels of audio quality in some objective sense or that a certain bit rate and codec is "good enough" for all listeners in all situations.

Everyone probably needs to develop their own guidelines for what they consider to be good enough streaming audio, based on their own listening experience, but I offer my experience, here, as an example and a starting point for comparison.  When I first began exploring what internet radio had to offer, two popular sites stood out for me. I found myself listening to Radio Paradise quite a bit, because I enjoyed their selection of music and because I found that their 192 kbps MP3 audio stream was easy to listen to. By this, I mean that I could enjoy listening to it for extended periods of time without it wearing on me. The other site that I found intriguing and spent quite a bit of time exploring was Pandora Radio. However, I noticed that I would get tired of listening to Pandora after an hour or so. At the time, Pandora was offering a free 128 kbps MP3 audio stream to subscribers, and it was free of the the audio advertising that they later inserted into it. While it is possible that I just didn't like the content of the "radio stations" generated by Pandora, as much as I liked the play lists on Radio Paradise, I believe that the primary difference between the two was the lower bit rate of Pandora's audio. Consequently, I developed the rule of thumb that 192 kbps MP3 audio was good enough for me to fully enjoy, while 128 kbps MP3 audio was less enjoyable, especially for extended listening.

Ideally, this means that I would delimit my listening to stations streaming at 192 kbps or higher; the problem is that this represents only a small percentage of what is available (especially if you prefer not to have to pay for your listening). So, when I am looking at internet radio streaming at less than 192 kbps, I start to attend more to the codecs being used. As a general rule, when bit rates decrease to 128 kbps and less, MP3 tends to lose fidelity more quickly than other codecs do. For this reason, I'll give a second look to a lower bit rate station, if it is available in a format other than MP3. Roughly speaking, a 64 kbps AAC+ stream comes close to the quality found in a 128 kbps MP3 stream, and a 128 kbps AAC stream seems to be in the same ballpark as a 192 kbps MP3 stream. Microsoft's latest WMA codecs (Windows Media 9 or higher) appear to be comparable to AAC+ with regard to their quality at the lower bit rates. Ogg probably comes close to the AAC codecs in quality at the lowest bitrates, as well. Radio Paradise has recently added some Ogg streams to their internet radio offerings, which will give me a good opportunity to become more familiar with this codec. For what it is worth, Radio Paradise claims "The sound of our 96k Ogg stream compares favorably to even our 192k MP3 stream, and our new 192k Ogg stream sounds even better."

Computer Media Players

Of course, to listen to any audio on your computer, you'll need a media player. Microsoft includes Windows Media Player with their operating systems, and Apple includes QuickTime with theirs. These two default media players each have their limitations with regard to what codecs they support. They both support MP3, but they are weaker in their support for open source codecs, such as FLAC and Ogg Vorbis. They tend to cater to their own proprietary codecs, instead. Windows Media Player supports WMA files, and QuickTime supports M4A and other AAC based files. Unfortunately, Windows Media Player does not include AAC support. Apple offers a version of QuickTime for Windows, and Microsoft has a Mac version of their media player.  (There also is a third-party developed plug-in available for QuickTime, which allows it to play windows media files.)

This proprietary approach to media players leaves room for third parties to offer more comprehensive solutions. WinAmp is one of the best known of these, having been around since 1997. It has the capability of playing more kinds of audio files than either Windows Media Player or QuickTime alone. It includes support for Microsoft's WMA files and for AAC. It also includes a browser for finding Shoutcast internet radio stations and AOL Radio channels. WinAmp is a windows application; there are no Mac or Linux versions. The basic version is free (and really all you need), but you can also purchase a "Pro" version for $20, which offers a few extra features for ripping and burning CDs.

Foobar2000 is completely free media player for windows (again, no Mac or Linux versions). Like WinAmp, it supports almost all types of audio files, including windows media audio. It has a less cluttered look than WinAmp, since it doesn't include any advertising in its user interface. Audiophiles seem to prefer this player, perhaps because of its functional design and the fact that it offers a wide selection of plug-ins, which provide additional features.

VLC is another completely free media player, which is being developed as an open-source project. This project appears to be rather ambitious with regard to the number of operating systems that it runs on, as well as the number of different media types that it opens. VLC versions are available for Windows, Macs, and many flavors of Linux. VLC handles all the audio formats that we've been discussing, and it can play many types of video, including DVDs. Because this is an open source project, it will always be a kind of work in progress. Nevertheless, since version 1 was released (we are currently up to version 1.1.11), it seems that this program has matured. If the idea of using an all-in-one media player appeals to you, or you happen to be running a Linux computer, or you are just looking for a free software DVD player, you might want to give VLC a try.

In addition to the stand alone media players described above, browser-embedded players are becoming increasingly prevalent. These function as plug-ins for your web browser. More often than not, the player in use is Adobe's Flash Player. These embedded media players provide a simple and straightforward interface for online stations to deliver audio to their listeners, and many people will appreciate how easy this makes listening to online music. However, unless the web site that you're visiting has taken the time to spell this out, you can't really tell what codec or bit rate these embedded players are using. (Flash can supports both MP3 and AAC.) Since knowing what an audio stream's bit rate and codec are is important to me, I still prefer being able to connect to an internet radio station using a stand alone media player whenever this is available.

What's Out There?

In this last section I would like to share some internet radio sites that I find interesting. If you are just getting started, these links might provide you with some ideas of where to begin. Even if you already have been listening to music online, perhaps you can find something new, here.

Radio Paradise: This is my favorite internet radio station. It offers an eclectic blend of music, which is rooted in both new and classic rock, but it includes other genres, as well. Adult contemporary probably is the label that comes closest to characterizing their play list, but this really is too narrow. What makes their play list stand out, for me, is that it is created completely by the DJs involved, and I'm convinced that DJs with a personal knowledge of a broad range of music will always be capable of creating a more interesting play list than one that is computer generated. Since the DJs behind Radio Paradise have a taste in music that is close enough to my own, I often find myself being introduced to new music that I end up enjoying. This internet-only station is listener supported. There are no ads, and the station breaks are brief.

Radio Paradise offers a number of different streaming choices. For a long time, their highest quality options were a 192 kbps MP3 stream and the 128 kbps AAC stream, but they have recently added a 192 kbps Ogg stream, which seems to offer better quality than the comparable MP3 stream. They also have a flash player option (labeled "click here to start listening") available on their web site, which makes use of their 128 kbps MP3 stream.

KEXP - Seattle: I mention this site as much for the novelty of it, as for the music that it plays. This station is very unusual in that it offers an uncompressed audio stream. Yup, a full 1.4 mbps, just like what comes off of a CD. They also have some more typical bit rates to chose from. This station is a college radio station that emphasizes indie artists.

Classical Music from Europe: A lot of classical music stations in Europe offer an online option, and quite a few of these are streaming at high quality bit rates.

AVRO Netherlands: AVRO has a number of stations broadcasting classical music in bit rates from 256 kbps up to 320 kbps. Here's a list of AVRO's web radio stations. Clicking on a particular station from that page activates a link to a web address using the Shoutcast playlist format; these can be opened by QuickTime, WinAmp, Foobar2000, and VLC, but not Windows Media Player. AVRO also has a flash based web player; select a music channel from the list (those marked with a radio antenna icon are available over the web).

(Try Google's translation feature, if you would like some help understanding more of what is written on the AVRO web site. Simply put the web address for the AVRO page into the translation page, and Google will give you a workable translation of the Dutch to English.)

Below are the three AVRO stations that I typically listen to (again, these are Shoutcast links with the .pls, playlist, file extension).

AVRO Light Classical High Definition (320K MP3)

AVRO "Best of the Best" (256K MP3)

AVRO Baroque around the Clock (256K MP3)

Radio 4 Netherlands: They offer classical music streamed at 160 kbps in WMA (Windows Media Player). If you access their music using the embedded flash player found on their site's main page ("Luister Live"), under Themakanalen, you'll find a couple of other classical options: Jong Klassiek (young performers) and Eigentijds (contemporary classical music). The main channel seems to stream at 192 kbps through their flash player, while the secondary channels appear to be steaming at 128 kbps; all probably are MP3.

Concertzender Netherlands: They offer classical, jazz, world, and other music programming, by way of a 192 kbps MP3 stream. By following the "Concertzender" link, above, you can click on the "Luister Live" link at the top of their home page, and this brings up their embedded Flash player, which connects you to the same source as my "192 kbps MP3" link. You'll also see a number of themed music channels, listed along the right hand side of their main page. These offer everything from medieval to popular contemporary music. These channels stream at 128 kbps, in MP3 format.

Check Radio The Check Republic: The link takes you to a list of all the many Check Republic radio stations streaming on the internet, and in this list, you can see links to the huge variety of bit rates and types of codecs that they make available. D-Dur Radio and Vltava Radio offer classical music programming (my links are to the 256 kbps Ogg streams, which will open with WinAmp, Foobar2000, or VLC).

NRK Radio Norway: NRK's classical station is available as a 384 kbps WMA stream. They also offer a jazz station, which is available as a 160 kbps WMA stream and a 192 kbps MP3 stream. (The "NRK Nettradio" button on their main page opens an embedded player that offers their MP3 streams, the highest being 192 kbps. See this NRK page for more information about their current internet audio offerings.)

Here's a site that offers an exhaustive list of streaming European radio stations. You can browse the site's lists by country or by type of music you are interested in. Operacast also provides links to classical music stations (both European and domestic), but I'm not sure how well they are keeping this information up to date.

Shoutcast provides a platform for creating and broadcasting internet radio stations. They also make available a directory of these stations, which can be browsed from within the WinAmp media player or by going to the Shoutcast Radio web site. You can listen to these streams on the web site by way of their embedded Flash media player. (WinAmp's built-in Shoutcast browser seems to provide a more up to date listing than the web site does.)

Customizable Internet Radio Stations: While the internet radio stations that I've provided links to, so far, are similar to over-the-air radio stations (and often are simulcast versions of these broadcasts), there is another kind of internet radio that lets you personally customize a channel's play list to match what you are interested in.

Pandora is perhaps the best known example of this kind of internet radio. You provide some input to the web site, such as the name of an artist or a song (or better, you provide lists of artists and songs), and the web site programs a play list for you. You can further refine the play list, while listening to it, by giving the current track a thumbs up or thumbs down. Pandora offers a free version of their service, which is supported by audio ads. This free service streams at 64 kbps, using the AAC+ codec. They also have a $36 a year premium service, which offers an ad-free, 192 kbps, MP3 stream. Pandora apps are available for many types of smart phones, but these apps only offer the 64 kbps AAC+ stream, at this time.

Bluebeat: Here you create your own play lists for free by combining music tracks from among the many available on their site. The limitation, here, is that your play list must have enough variety to keep the recording industry happy. Consequently, when you create a play list, Bluebeat requires that it include a minimum of 10 artists, a minimum of 10 albums, and at least 30 songs. Bluebeat streams their music at up to 360 kbps through their web based player. (You have to complete the free registration process in order to see the 320 kbps configuration option, but you need to be registered to create play lists, anyway.)

Grooveshark: This site seems to be operating in a legal gray area. The model that they are using is reminiscent of how Youtube operated early on. Users uploaded content to the site, and others can access it. However, the site proclaims no responsibility for what is being uploaded to it. Grooveshark says that they will take down any content that a legitimate right's holder objects to, but it is incumbent upon these right's holders to file such a claim.

We know how this ended for Youtube. The recording industry forced them to clamp down, and they now strip away any copyrighted music track added to a video, requiring the person uploading the video to show that he or she has permission from the recording industry to use the music.

Nevertheless, at this time, Grooveshark has a large collection of music that can be listened to (the tracks are played in 192 kbps MP3 format via their embedded player). Without the restrictions found on sites like Bluebeat, you can queue up a whole album to listen to, from beginning to end, or select just a single track by a particular artist. Since the tracks have all been uploaded by users, I wonder about the quality of the audio provided. Grooveshark simply requires that it be at least 128 kbps in format for upload. Therefore, it seems possible that their 192 kbps stream will include audio that really is of lesser quality; however, I've not noticed this to be an issue in actual listening. (They report that they use the highest bit rate uploaded, when they receive multiple uploads of the same track.) Since this is user uploaded content, you'll notice a lot of duplicated material, because of things like spelling mistakes in a track's title or other small labeling discrepancies that aren't picked up on by Grooveshark's cataloging process.

MOG: This site doesn't offer a free service (only a 2 week free trial). The basic service is available for $5 a month, and there also is a $10 a month service that includes support for mobile phones. The desktop service is streamed at 320 kbps, using MP3 format, while the mobile version streams at 64 kbps using AAC. Basically, this sounds like a more legal version of what Grooveshark offers. You are free to select music by the track on MOG and create a play list in this fashion. There also is a "Radio" version, which will create a play list based on your selection of an artist. You can use a slider to delimit this play list to only the artist selected or allow the inclusion of other, similar artists, as well.

Spotify: This is another site which allows you to select and listen to music by the individual track. The service was started in Europe, but recently they have introduced availability in the US. Unlike MOG, they offer a free, ad-supported service, in addition to their premium options. The free service is by "invitation", but you can apply for one of these invitations at their web site. The first six months of this free service are a kind of a demo period during which there are no restrictions on number of tracks played or number of hours it is listened to. After that, free account users are restricted to 5 plays per track and 10 hours of total listening per month. The free service uses a 160 kbps Ogg audio stream. $5 a month upgrades a user to their Unlimited account, which gets rid of the ads and the monthly limitations. $10 a month upgrades a user to their Premium service. In addition to being ad-free, the Premium service offers a higher bit rate option (320 kbps Ogg) and versions of their player that are compatible with various smartphone operating systems. Spotify also emphasizes features that make it easy to share music and play lists through social media web sites, such as Facebook and Twitter.

Jango, Slacker, and Last FM are some other music web sites with customizable play lists. These three fall into my honorable mention category, primarily because they only offer 128 kbps MP3 streams. Nevertheless, they are interesting alternatives to Pandora's 64 kbps free service.

NPR: While not exactly offering your typical internet radio station (though many of the affiliated local broadcast stations do simulcast over the internet), you can find some worthwhile content to listen to here, especially in the music sections. For example, they often have music tracks available, which are related to albums that they have reviewed or artists who they have interviewed. Some of this content is exclusive to the web site. The music section's associated music tracks are accessible through NPR's embedded Flash player. Although I'm not sure what codec is used, it appears that the audio is streamed at around 128 kbps.

Local Stations: Finally, I'll mention a couple of local FM radio stations on the web: WUOT, Knoxville (91.3 FM) and WDVX, Clinton (89.9 FM) and Knoxville (102.9 FM).

WUOT is a public radio station associated with the University of Tennessee. Since they put out such a strong FM signal, locals will hardly need to go online to hear what is being broadcast over the air. However, WUOT now offers a second station, WUOT-2, which has its own unique programming. This second channel is available to those with a HD Radio, and it is available over the internet. Although WUOT had some higher bit rate options at one time, they currently offer a 192 kbps stream in MP3 format and another 192 kbps stream in WMA format. Follow the Listen Online links, on WUOT's website, to go to a page where you can select between WUOT-1 and WUOT-2 and then choose the kind of audio stream that you'd like to use.

WDVX: This local station is non-commercial and offers up Blue Grass and Americana style programming, which is a pleasant alternative to Nashville's country sound. The very low power output (only 200 watts from their Briceville transmitter and probably about 10 watts from the Knoxville repeater) means that the likelihood of getting a strong, clear signal is pretty small. Thus, their internet simulcast is probably your best choice for listening to this station, even though they only offer 96 kbps as their highest quality option (96 kbps MP3 (Shoutcast) and 96 kbps WMA).

If you've gotten this far, thanks for reading, and I hope that you've found it worthwhile and that you're now on your way to enjoying lots of good music.

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[Revised September 16, 2011. Ver. 2.0]