Here is a PowerShell script for converting music for upload into Cisco Unified Communications Manager (CallManager). Of course this can be used for other call processing systems, though the ideal codec/bitrate may vary. CUCM does some internal conversion of the file, but many people experience pops/crackles and poor quality overall. This may be due to trying to upload a file that is too high of quality.
Try MTU sizes until you reach one that doesn’t work!!
NOTE: Cisco IOS has a feature built-in to do an MTU sweep!