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The Shortwave Radio of the Internet: Low Bitrate Streaming

While updating the 2004 podcast entries for my old radio show “mediageek” I was reminded that I used to post the episodes in both a 64kbps mono “broadcast quality” MP3 and a 16kbps.

The reason why I posted such a low bitrate file, containing relatively low fidelity, was to make the show accessible to listeners who did not have access to broadband internet, or whose access was limited. You see, in 2004 broadband penetration in the United States was just barely approaching 50%, meaning that half of households with internet were still using dial-up modems.

In the best case scenario, it would take a 56kbps modem user about 35 to 40 minutes to download the weekly half-hour “broadcast quality” MP3. That’s longer than real-time, and assumes a very quiet phone line, good connection and no internet multi-tasking, like checking email or surfing the web while downloading. Though I actually had DSL broadband when I launched the show in 2002 and began posting shows online, listeners from around the world had emailed me asking for smaller files.

I first settled on 16kbps because the typical show was about 3.5 MB, or about a fifth the size of the “broadcast quality version.” That file could be downloaded in nine or ten minutes by a modem user.

As I alluded, the sound quality of that 16kbps file isn’t great. But, it’s also perfectly intelligible. Fidelity-wise I’d compare it to shortwave radio, and utterly adequate for a talk program, which is what “mediageek” was.

Hear 16kbps for yourself:

I quit posting those low bitrate files in the middle of 2005, in part because of the extra effort it required, and in part because I assumed that listeners’ internet connections were improving. Turns out, I was mistaken on the latter point. I received several emails telling me that only having bigger 64kbps files was making the show inaccessible, with one listener suggesting that 24kbps files would be an acceptable compromise between file size and fidelity. The sound was more like AM radio than shortwave. So I resumed creating smaller files at this bitrate.

Here’s what one of those 24kbps files sounds like:

The Magic of Shortwave, Online

As I mentioned in my post about the history of internet radio, this is the kind of sound quality I was accustomed to when streaming audio from around the world in the mid- and late–90s over my home dial-up connection. The experience then was very much like the first time I used a shortwave radio as a child. It was pure magic to hear live radio from thousands of miles away, or on-demand recorded shows that I’d never otherwise have the opportunity to hear before.

Though the fidelity was shortwave-quality, the listening experience was more rock-solid. No signal fades, static or lightning strikes intruded on those early internet broadcasts, provided nobody else picked up the phone. I happened to live alone in a one-bedroom grad student apartment, and so was lucky not to have to compete for the line.

Since that time most people with internet access are now accustomed to getting better bandwidth oner 4G mobile connections than we did with modems or even early 2000s cable and DSL home broadband. It’s no problem to stream high quality stereo music from Spotify or Pandora on the go. Certainly makes those 16kbps MP3s seem obsolete.

Or are they?

Low Bitrate Streaming Today

Internet bandwidth is not unlimited, especially over mobile connections. Many folks either pay by the gigabyte or have firm bandwidth limits every month with stiff charges for going over limit. Until this past October my own mobile plan limited my wife and me to 2 GB combined, which required me to limit the podcasts and music I streamed or downloaded over mobile broadband. Podcast files clocking in at 50 MB or more really do add up quickly.

I wonder how many listeners would gladly trade in some loss in fidelity in order to moderate their bandwidth usage? Moreover, many rural communities across the U.S. are still considered “broadband deserts” where home and mobile speeds are very slow, or where dial-up is still the only option. Bitrate and file size can still be a matter of accessibility.

Offering lower bitrates is less of a sonic compromise today than it was 15 years ago, due to advances in codec technologies. MP3 is relatively ancient compared to the more modern AAC, which has many variants, including a “high efficiency” (HE) version designed specifically for low bandwidth applications. This is great for streaming, but still not so hot for podcasting. That’s because MP3 is pretty much the de facto standard for the medium – for a variety of reasons – and while most modern podcast players can play other file types, MP3 guarantees the broadest compatibility.

But sticking with MP3 significantly limits low bandwidth sound quality, which is why I’m reluctant to reduce the bitrate for the Radio Survivor podcast in order to get smaller file sizes (right now the show averages around 26 MB).

However, I recently noticed that Mixcloud, which streams DJ mixes, radio shows and podcasts, uses AAC-HE, likely for the purpose of conserving bandwidth costs. A recent episode of Radio Survivor hosted there is actually re-encoded to 49kbps variable bitrate mono AAC-HE file; our normal MP3 podcast file is 64kbps mono. It sounds just fine to my ears:

I don’t know if the platform adjusts bitrates for lower bandwidth users – I tend to doubt it. However that 49kbps bitrate is just low enough that you can probably stream it over a modem or 2G mobile connection, perhaps with some initial buffering. (That’s not something I can test, since I don’t have a modem or landline.)

Where Are the Low Bitrate Stations?

To see if there appears to be any demand for low bitrate internet radio I checked out the directory at Shoutcast, which is one of the only directories where you can easily sort stations by bitrate. Just looking at the top stations list I can see more than three dozen stations streaming at under 64kbps, with 32kbps seeming to be the most popular low bitrate, using both MP3 and AAC. Looking only at talk radio stations, there are even more low bitrate streams.

It’s not just about accessibility. It also helps to control bandwidth costs for the station. But seeing the wide availability of these streams tells me there are still people listening to them. They may not be specifically looking for low bitrates. They might just be selecting particular streams based upon whether or not they play readily and easily over their connection.

True to my analogy, many international shortwave broadcasters offer low bitrate streams. For instance, the BBC World Service offers streams as low as 48kbps.

In any event, while low bitrate streaming may not be much needed by many of us with always-on broadband connections, there still seems to be a need, even if the format flies mostly under the radar. The ability to squeeze down an audio signal into a tiny stream means we can still get internet radio broadcast from far away places or receive it in places where internet is still a limited commodity.

In that way, the spirit of shortwave radio is still alive on the internet today.

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