MP3 player with Network Connection

Student: Michael Somersmith

Supervisor: Peter Sutton

Category: Engineering Thesis Project - Computer Systems

Compressing raw audio with the MP3 standard can reduce the storage space required by approximately one tenth. This has made it possible to play audio from devices with limited storage space, for example mobile phones, PDA’s and flash based MP3 players. Their small size also makes them more convenient and flexible to use than using traditional audio CDs. It is now possible to buy MP3 players that can play MP3s from a CD containing ten or more albums or from a hard drive containing hundreds of albums.

Another advantage of their small size is that they are very suitable for transferring between devices, whether it be through USB, cable based networks or wireless networks. This allows for the MP3s to be played in a remote location from where they are stored. For a long time now people have been doing this on computers to play MP3s that are stored on other computers connected via a LAN or the internet. Up until now this has been limited to computers. The aim of this thesis is to produce a MP3 player that can play MP3s that are stored on computers connected to it through a LAN or internet connection. This enables the user to be able to play MP3s that are stored on computers without being in the same environment as the computer.

The project was broken into two parts: development of an embedded MP3 decoder with a network interface, and a server program on a PC to communicate to the player and windows. The networking on the player was performed using an Ethernut development board. The Ethernut is an open source hardware and software project. The hardware uses an Amel ATmega103 processor with a Realtek 8019 network controller and the software is the Nut/OS, which is a real-time operating system and Nut/Net, which provides networking APIs and a fully featured TCP/IP stack. The software developed on the player streams the MP3 data from the server program on the PC through a TCP connection. The server program determines which MP3 to stream by reading a standard Winamp play list file. From this file it also determines the song title and sends it to the player which receives the song name and displays it on an LCD. On the player the MP3 stream is received and stored in a buffer which in turn is sent to the MP3 decoder, the VS1001k. Whenever the decoder needs more data it raises an interrupt and the program feeds it data through a serial interface. A user is able to control how the music is played through standard track controls: play/pause, stop, next and previous track. The player decodes these and sends them as commands to the server which will either modify the data stream accordingly (i.e. Stop or pause) or go back to the Winamp play list and open a new file to stream (i.e. next and previous).

The final implementation of the player operates as you would hope it to. It can play MP3s that are stored anywhere on the network, whether the data be on the computers hard drives or on a CD in their CDROM drives. All sample rates are supported and all bit rates can be played up to 250kbbs, including variable bit rates. The user can navigate through the play list using the controls on the player and the song name selected is displayed on the LCD. The audio that is produced is of CD clear quality at a line out level ready to be connected to the line in of a stereo.

Thesis Document (PDF)