it did not work when i wanna convert local audio files

[airrons]

i just don't know how to use this convert tool self.transcoder = [[DGAudioTranscoder alloc]initWithURL:audioUrl transcodingToUrl:desUrl]; self.transcoder.delegate = self; self.transcoder.outputAudioFormat = kAudioFileM4AType; self.transcoder.doneBlock = ^(DGAudioTranscoder * transcoder){ NSLog(@"======"); }; [self.transcoder start];

but it just do not work at all and the protocol method did not called