Recording Messages Using The Same Codec as The Incoming Call

My situation:

I am working on a project in which the recorded messages need to be of the highest quality possible. I also want to minimize transcoding on the Asterisk server. I have set Asterisk to only accept incoming calls using the G711 mu-law codec so the incoming voice stream is as high quality as possible.

My questions:

  1. In what format should I record the messages so G.711 mu-law is the codec used in the resultant audio files?

  2. If the above format is not .wav, what kind of performance hit should I expect to record an incoming G.711 mu-law audio stream as a .wav file?

Thanks,

James Linder