Internet radio is an audio service transmitted via the Internet. Broadcasting on the Internet is usually referred to as webcasting since it is not transmitted broadly through wireless means.
Internet radio involves streaming media, presenting listeners with a continuous stream of audio that typically cannot be paused or replayed, much like traditional broadcast media.
Internet radio services offer news, sports, talk, and various genres of music—every format that is available on traditional broadcast radio stations.
Many Internet radio services are associated with a corresponding traditional (terrestrial) radio station or radio network, though with a potential worldwide audience
Internet radio is typically listened to on a standard home PC or similar device, through an embedded player programme located on the respective station’s website.
More and more are listening on one of the many standalone Internet radios available.
Wifi /Internet Radios
A Wifi Radio is also called Internet Radio, it is a radio receiver that receives station that broadcasting over the internet.
These radios are built with a WiFi connection to the internet, so they are often called WiFi Radios. More than 20,0000 radios all over the world can be found on the internet, most of the current AM, FM stations are broadcasting in a traditional way “On Air” as well as on the internet, so you have a chance to listen to these stations from the internet worldwide.
Internet radios are built with different modules. Different factories use different solutions to build up their radios, so the chips used inside radios are not the same.
There are a few parts on the radio:
- Internet connection
- Codec for the streaming data from the URL
- Amplifier
- Speaker.
It streams in the data from the URL, most WiFi radios need portal support to stream in the station.
The portal website stores hundreds of thousands of station that the radio will retrieve from it.
Different brand radios use different portals to have their stations supported.
For live stream see:
Radiofeeds
Bitrates
Data compression is also applied in ‘Internet Radio’ streaming. When audio is compressed in such a way through a streams encoder (regardless of the format the audio’s signal is coming from) the lower the stream bitrate used, the lower this will be in the occurring sound quality.
The audio will begin to lose certain frequencies through the compression. Any really low frequency’s such as a bassline in the music will begin to sound less defined and the high-end frequencies will begin to show the compression artefacts more evidently.
The amount of data a radio stream retains is measured in kilobits per second (Kbps). The higher the kilobits, the more data stored and the higher the audio quality.
Bitrate describes the rate at which bits are transferred from one location to another. It measures how much data is transmitted in a given amount of time.
Bitrate is measured in bits per second (bps), kilobits per second (Kbps), or megabits per second (Mbps).
Bitrate can also describe the quality of an audio or video file. For example, an MP3 audio file that is compressed at 320 Kbps will have a greater dynamic range and may sound more clear than the same audio stream compressed at 128 Kbps.
This is because more bits are used to represent the audio data for each second of transmission.
Advanced Audio Coding (AAC)
Advanced Audio Coding (AAC) is an audio coding standard for lossy digital audio compression. Designed to be the successor of the MP3 format, AAC generally achieves better sound quality than MP3 at similar bit rates.
AAC has been standardized by ISO and IEC, as part of the MPEG-2 and MPEG-4 specifications.
Part of the AAC known as High-Efficiency Advanced Audio Coding (HE-AAC) which is part of MPEG-4 Audio is also adopted into digital radio standards like DAB+ and Digital Radio Mondiale.
AAC supports the inclusion of 48 full-bandwidth (up to 96 kHz) audio channels in one stream plus 16 low-frequency effects (LFE, limited to 120 Hz) channels, up to 16 “coupling” or dialogue channels, and up to 16 data streams.
The quality for stereo is satisfactory to modest requirements at 96 kbit/s in joint stereo mode; however, hi-fi transparency demands data rates of at least 128 kbit/s (VBR). The MPEG-2 audio tests showed that AAC meets the requirements referred to as “transparent” for the ITU at 128 kbit/s for stereo, and 320 kbit/s for 5.1 audio.
AAC is the default or standard audio format for YouTube, Android, iOS devices, BlackBerry, and webOS-based mobile phones.
No licenses or payments are required to be able to stream or distribute content in AAC format. This makes AAC a much more attractive format to distribute content than MP3, particularly for streaming content like Internet radio.
AAC Plus (HE-AAC)
HE-AAC (High-Efficiency AAC, also known as AAC+, is audio compression technology that provides near-CD-quality using very little network bandwidth.
It combines MPEG AAC and SBR (Spectral Band Replication) technology. This combination increases the efficiency of MPEG AAC, resulting in superior fidelity compared to MP3, Windows Media, Real Audio, and Ogg Opus at bitrates of 64 kbps and lower. (At 96 kbps and higher, pure AAC offers similar advantages over these older codecs.)
HE-AAC at 48 kbps can produce better subjective quality than MP3 at 128 kbps, 128 kbps is no longer needed to achieve high-quality streaming.
HE-AAC can create better audio quality at lower bitrates than the older MP3 and WMA, it is no longer possible to assess streaming audio quality by bitrate alone.
Commercial consideration must also be taken in to account, MP3 streaming requires paying 2% of revenue for streaming royalties. The only way to avoid this is to have non-profit status, however, commercial radio stations and do not qualify.
HE-AAC is natively supported in Adobe Flash, Microsoft Windows 7/8, Apple OS/iOS, and most mobile phones. More listeners than ever are accessing live radio streams on their mobile devices.
MP3 Streaming
MP3 streaming is still very common and well supported by computers and stand-alone Internet radio.
The technology is outdated and is being replaced by other formats.
MP3 streams are not as efficient as AAC streams, so broadcasters need to use more bandwidth and pay royalty fees for using the technology.
Constant bitrate vs. Variable bitrate
To further complicate the bitrates, many encoders allow customising the encoding process by selecting either constant or variable bitrates.
Constant Bitrate encoding (CBR) maintains a steady bitrate stream through the entire mp3 stream. This means a consistent level of compression and predictable bandwidth usage.
Settings range from 16 kbps to 320 kbps depending on the stream size. Streams encoded higher than 128 kbps may have little or no detectable improvement in sound quality, though greater bandwidth will be required.
CBR has its drawbacks, especially when encoding certain kinds of music or speech. Constant Bitrate encoding does not take these factor into consideration and maintains a constant reliable bitrate.
Broadcasters run the risk of using more bits at times than is necessary.
To address the shortcomings with constant bitrate encoding, Variable bitrate encoding (VBR) was developed.
VBR makes intelligent decisions before allocating its bits to the encoding process. It adapts the bit rate to the complexity of the audio, based on a scale that be can set in the preferences of the encoder. The low end of a scale from 1 to 100 would result in the lowest quality/highest compression. The high end of the scale would result in the highest quality/lowest compression.
The overall quality is a better and more consistent sound quality compared to CBR encoding at the same bitrate.
| MP3 Stream Quality | |
| Bitrates (Kilobits per Second) | |
| 32 kbps | AM radio quality |
| 64 kbps | About the same quality as an FM radio station |
| 96 kbps | FM radio quality |
| 128–160 kbps | Good quality. Differences from the original audio source can be noticeable. |
| 192 Kbps | Medium quality. Slight differences from the original audio source can be heard. |
| 224–320 kbps | High quality. Little loss of audio quality from the original source is noticeable. |
|
|
|
| AAC compared to MP2 used by DAB in the UK | |
| 128 kbps AAC provides the same level of audio quality as 256 kbps MP2. 96 kbps AAC+ provides the same level of audio quality as 192 kbps MP2. 64 kbps AAC+ provides the same level of audio quality as 128 kbps MP2. |
|
HTTP Live Streaming (HLS)
HTTP Live Streaming (HLS) is an adaptive streaming communications protocol created by Apple to communicate with iOS and Apple TV devices and Macs running OSX in Snow Leopard or later. HLS can distribute both live and on-demand files and is the sole technology available for adaptively streaming to Apple devices, which is an increasingly important target segment to streaming publishers.
HLS is widely supported in streaming servers from vendors like Adobe, Microsoft and RealNetworks.
The popularity of iOS devices and this distribution-related technology support has also led to increased support on the player side, most notably from Google in Android 3.0.
HDS
HDS – HTTP Dynamic Streaming was developed by Adobe as an alternative to their RTMP protocol. HDS allows for adaptive streaming over HTTP to any device that’s compatible with Adobe Flash or Air.
