Yesterday，I port UCOSII to SAM3U-EK borad,and then develop a MP3 programmer base on UCOSII.
There also has a MP3 programmer base on Coocox OS,you can get the source code from http://www.coocox.org/EXAMPLE/ATMEL_Keil_ARMCC.htm.
The two MP3 programmer both runs very well.
For what is Coocox OS,you can visit http://www.coocox.org.
Hope it help for you,thank you