These are just a few Codecs used in Voice over IP devices though you’ll probably find that G.711 is used the most.

• iLBC - @ 15Kbps = 20ms frame size and @ 13.3 Kbps = 30ms frame size
  
  
• G.711 - 64 Kbps usually 20ms frame size
  
  
• G.723.1 - 5.3/6.3 Kbps, 30ms frame size
  
  
• G.729 - 8 Kbps, 10ms frame size (sometimes 20ms)
  
  
• Speex – From 2.15Kbps up to 44.2 Kbps – frame size = variable