语音编解码与带宽计算关系

    VOIP Bandwidth consumption naturally depends on the codec used.

    When calculating bandwidth, one can't assume that every channel is used all the time. Normal conversation includes a lot of silence, which often means no packets are sent at all. So even if one voice call sets up two 64 Kbit RTP streams over UDP over IP over Ethernet (which adds overhead), the full bandwidth is not used at all times.

    A codec that sends a 64kb stream results in a much larger IP network stream. The main cause of the extra bandwidth usage is IP and UDP headers. VoIP sends small packets and so, many times, the headers are actually much larger than the data part of the packet.


Codec       BR          NEB
G.711       64 Kbps     87.2 Kbps
G.729       8 Kbps      31.2 Kbps
G.723.1     6.4 Kbps    21.9 Kbps
G.723.1     5.3 Kbps    20.8 Kbps
G.726       32 Kbps     55.2 Kbps
G.726       24 Kbps     47.2 Kbps
G.728       16 Kbps     31.5 Kbps
iLBC        15 Kbps     27.7 Kbps

BR = Bit rate
NEB = Nominal Ethernet Bandwidth (one direction)

根据我的使用经验，

8K的G.729加上IP封装后达到32K,

为了防封杀，还有的用户使用IP Sec设备将语音做成VPN，这样G.729加上IP封装，再加上VPN会达到60多K。