CCNA, CCNP, MCSA, CCNA Final Exam, All Answer Test Module With 100/100

I reading song from iPod library using assetUrl (in code it named audioUrl) I can play it many ways, I can cut it, I can make some precessing with this but... I really don't understand what I gonna do with this CMSampleBufferRef to get data for drawing waveform! I need info about peak values, how I can get it this (maybe another) way? AVAssetTrack * songTrack = [audioUrl.tracks objectAtIndex:0]; AVAssetReaderTrackOutput * output = [[AVAssetReaderTrackOutput alloc] initWithTrack:songTrack outputSettings:nil]; [reader addOutput:output]; [output release]; NSMutableData * fullSongData = [[NSMutableData alloc] init]; [reader startReading]; while (reader.status == AVAssetReaderStatusReading){ AVAssetReaderTrackOutput * trackOutput = (AVAssetReaderTrackOutput *)[reader.outputs objectAtIndex:0]; CMSampleBufferRef sampleBufferRef = [trackOutput copyNextSampleBuffer]; if (sampleBufferRef){/* what I gonna do with this? */} Please hel