Getting problem while converting AAC to Mp3 using FFMPEG-Libavcodec

I have to convert AAC file to Mp3 in my project for detecting BPM.

I installed FFMPEG and i added all the library and i am not getting any compiler error but it crashes when i run the project.

I am getting following error,

[Session started at 2010-02-23 19:22:13 +0530.]
2010-02-23 19:22:14.641 New Decode[7170:10b] *** _NSAutoreleaseNoPool(): Object 0x20a2d0 of class NSCFData autoreleased with no pool in place - just leaking
Stack: (0x967a8f4f 0x966b5432 0x966c9b25 0x966c9701 0x2eb2 0x28de)
2010-02-23 19:22:14.649 New Decode[7170:10b] *** _NSAutoreleaseNoPool(): Object 0x20bcf0 of class NSCFData autoreleased with no pool in place - just leaking
Stack: (0x967a8f4f 0x966b5432 0x966c9b25 0x966c9701 0x2ed5 0x28de)
Audio decoding
[aac @ 0x1802000]channel element 1.0 is not allocated
Error while decoding

The 开发者_运维技巧Debugger has exited with status 1.The Debugger has exited with status 1.

Does any one have idea about it or having any sample code for it?.

Regards, CocoaDev.