[Freeswitch-users] Best sound file format for freeswitch

Hi,users. I have 1-100 sound files (mp3) and wants to play these files in loop from 1 to 100 to more than 250 concurrent users. Currently these sound files have format. Codec: MPEG audio layer 1/2/3 (mpga) Channels: Stereo Sample Rate: 22050 Hz Bitrate: 64 kb/s While playing these files I see in freeswitch log. *2015-04-23 14:17:59.351859 [WARNING] switch_core_file.c:230 File has 2 channels, muxing to 1 channel will occur.* I want my freeswitch to have minimum load while playing these files (located on freeswitch server). I which file format I must convert these files to have my freeswitch with minimum load. Your Guys opinion is much appreciated. Thanks