SolveYourProblem Article Series: Audio & Video Streaming
Streaming FAQ and Tutorials

What Is Streaming Audio?

Have you ever opened a web page and heard music playing in the background? Or have you ever tuned into one of the many online radio stations? If so, then you have received audio streaming without being aware of it.

Streaming audio is audio, or sound, which is heard while it is being delivered, giving you a “live” link. It is a term that is applied only to audio that is sent over computer networks. “Stream” can also be used a verb, in which case it means to deliver the audio.

Audio streaming has been a long time in the making. Since computers were born, people tried to find a way to display media on them. In the beginning they were very limited by the high cost of computer hardware and the limited capabilities that it had. By the 1970s, they had the basics down, but it took until the 1980s before the average computer was strong enough to display various media. Even then, they found out that they needed enough CPU power and bus bandwidth to support the data, as well as low-latency interrupt paths to get the information out.

By the 1990s, the average consumer had access to greater bandwidth, increased access and commercialization of the Internet, and usage of standard formats. Now the average computer could handle streaming audio in a way that was practical and affordable.

Currently, there are two ways to listen to your audio stream. It can be on demand or live. On demand is audio that is stored on a server for extended periods of time, and then is transmitted when desired. Live is only available during that certain time frame that the event is showing, such as audio from a sporting event or concert that is sent as it is happening.

Streaming media requires a lot of storage and bandwidth in order to run. For example, a one hour video needs over 128 megabytes of storage space. You would need about 300 megabits per second of bandwidth just to be able to show it to 1000 people at once. This can require a pretty powerful server if the website or program is very popular.

There are many different ways to get your streaming audio out there, each with its own issues.

UDP, or User Datagram Protocol, sends the audio as a series of small packets. It is the simplest way to send the information. However, a packet can get lost or corrupted in transit, which can affect the final product that the receiver sees. RTSP (Real Time Streaming Protocol), RTP (Real-time Transport Protocol), and RTCP (Real-time Transport Control Protocol) were designed specifically for streaming media and were built on top of UDP.

TCP, or Transmission Control Protocol, can guarantee correct delivery of all of the information in the audio stream. However, this is done by timing out and retrying, which can make it difficult to get started. If data is lost on the network, the whole stream stalls while the missing information is transmitted.

Unicast protocols copy the media stream and send it from the server to each individual client. This is simple, but leads to massive data duplication. Along the same lines, multicast protocols send only one copy over any network connection, making it more efficient but harder to implement. Multicast is not often used for sending information over the Internet since it is blocked by most firewalls, but works well on private networks.

P2P, or peer-to-peer protocols arrange for media to be sent from computers that have it to ones that do not. However, this raises many issues, as was brought to light with Napster.

With all the information bouncing back and forth every second on the Internet, it is understandable that some broadcasters are concerned that copies will result in lost sales. They may try to encrypt the stream to prevent it from being copied after it has been downloaded. Currently, though, there are no foolproof ways to protect the information. As the technology grows, broadcasters will become more reliant on copyrights and patents to protect themselves.

Audio streaming is a fascinating way of sending sound from computer to computer, not only in the way it works but in the finished product as well. It will be interesting to see what the future has in store for us as this technology continues to advance.

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SolveYourProblem.com : 2008

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