AUDIO STREAMING

Spotify

The Swedish company Spotify AB was founded in 2006 by Daniel Ek and Martin Lorentzon and the official release of their audio streaming service Spotify was in 2008 after a long period of beta testing. It was the first streaming service with focus on bringing the era of piracy down. The bigger record labels as Universal Music Group, EMI, Sony Music Entertainment, Warner Music, Merlin and The Orchard have invested in the company.

Spotify is limited to a number of countries mostly located in Europe. The first release outside of Europe was in 2011 as they launched their service in the US. With around 16 million music tracks in its library(March29, 2012/spotify blog) makes it to the second largest streaming service to date. To be able to listen to music the user needs to have an account combined with the Spotify software. There are three types of accounts: Premium, Unlimited and Free where:

• Premium offers unlimited access to the music with possibility to store music for offline playback. The mobile version only works with the Premium version. The Premium also features quality up to 320 kbit/s.
   
• Unlimited has a lower quality than Premium and uses standard quality of 160 kbit/s. This version has as it name says unlimited access to online playback of all tracks.
   
• Freelimits the user to ten hours listening per month and between some tracks a short commercial is played. The whole music library is available to the user and the sound quality is the same as for Unlimited. Users registered less than 6 moths can only listen to a specific song five times a month.

In April 2012 Spotify had 10 million users and about one third were with the Premium version.

Spotify does not have a web based-application, using instead a user-friendly and efficient software. It can bring the latency, when switching tracks, down to just a few hundreds of milliseconds (median access time of 265 ms). The desktop version can use two qualities, q5 or q9, with bitrates of around 160 or 320 kbit/s where the latter is for Premium users only.

The software uses TCP package sending and  uses P2P transfer whenever possiblewhich leads to server usage of only 9% when compared to if no P2P is used. Every user has data cached in his computer that is shared between the other users on request. A common scenario is when a new song that is not in the local cache of the user is chosen, then the data is collected as follows:

• Get the first 15 seconds from one of the servers.
• Find peers in not too far distance to get the rest of the song (P2P).
• At the end of the song find peers that have the next queued song and load into cache.
• If no peers or too few are found continue from the server

Spotify recommends an internet connection of 256 kbit/s or greater to get the most out of the streaming service. Since the service uses local cache it will run more smoothly if more disk space is available.

Mobile devices use no P2P, instead all data comes from the servers. Streaming over a 3G-connection uses the third and lowest quality, q3, at roughly 96 kbit/s. Spotify has a contract with Facebook which enables users to easily share playlists and tracks with each other. A “radio” from Last.fm is also integrated in the service. The radio contains pre-made playlists and besides all music Last.fm has information about the artists behind it and Last.fm has a search engine to find local gigs.

www.spotify.com