SIP测试入门指南

常用音视频编解码

Payload type Name Type No. of channels Clock rate(Hz) Frame size(ms) Default packet size(ms) Description References
dynamic (or profile) AMR audio (various) 8000 20 Adaptive Multi-Rate audio RFC 4867
0 PCMU audio 1 8000 any 20 ITU-T G.711 PCM µ-Law audio 64 kbit/s RFC 3551
8 PCMA audio 1 8000 any 20 ITU-T G.711 PCM A-Law audio 64 kbit/s RFC 3551
9 G722 audio 1 8000 any 20 ITU-T G.722 audio 64 kbit/s RFC 3551 - Page 14
4 G723 audio 1 8000 30 30 ITU-T G.723.1 audio RFC 3551
dynamic G726-16 audio 1 8000 any 20 ITU-T G.726 audio 16 kbit/s RFC 3551
dynamic G726-24 audio 1 8000 any 20 ITU-T G.726 audio 24 kbit/s RFC 3551
dynamic G726-32 audio 1 8000 any 20 ITU-T G.726 audio 32 kbit/s RFC 3551
dynamic G726-40 audio 1 8000 any 20 ITU-T G.726 audio 40 kbit/s RFC 3551
3 GSM audio 1 8000 20 20 European GSM Full Rate audio 13 kbit/s (GSM 06.10) RFC 3551
31 H261 video 90000 ITU-T H.261 video RFC 4587
34 H263 video 90000 H.263 video, first version (1996) RFC 3551, RFC 2190
dynamic H263-1998 video 90000 H.263 video, second version (1998) RFC 3551, RFC 4629, RFC 2190
dynamic H263-2000 video 90000 H.263 video, third version (2000) RFC 4629
7 LPC audio 1 8000 any 20 Experimental Linear Predictive Coding audio 5.6 kbit/s RFC 3551
dynamic (or profile) opus audio 1, 2 48000 2.5–60 20 Opus) audio RFC 7587
dynamic (or profile) speex audio 1 8000, 16000, 32000 20 Speex audio RFC 5574
dynamic raw video 90000 Uncompressed Video RFC 4175
dynamic VP8 video 90000 VP8 video draft-ietf-payload-vp8
dynamic RED audio Redundant Audio Data RFC 2198

带宽计算公式:

带宽=包长度×每秒包数
=包长度×(1/打包周期)
=(Ethernet头+IP头+UDP头+RTP头+有效载荷)×(1/打包周期)
=(208bit +160bit+64bit+96bit +有效载荷)×(1/打包周期)
=(528bit+(打包周期(秒)×每秒的比特数))×(1/打包周期)
=( 528 / 打包周期 ) + 每秒比特数

按照上面的计算公式:

G711:20ms打包,带宽为 ( 528/20 + 64) Kbit/s=90.4 Kbit/s
G729:20ms打包,带宽为 ( 528/20 + 8 ) Kbit/s= 34.4 Kbit/s
G723:5.3k,30ms打包,带宽为 ( 528/30 + 5.3 ) Kbit/s=22.9 Kbit/s

业界一般按照下表提供的IP网带宽系数和以太网带宽系数来设计网络带宽:

编解码技术 压缩速率(Kbps) 打包周期(ms) IP网带宽系数 以太网带宽系数
G.711 a/u 64 20 1.25 1.41
G.729 a/b 8 20 0.38 0.54
G.723.1(5.3kbit/s) 5.3 30 0.27 0.37
G.723.1(6.3Kbit/s) 6.3 30 0.25 0.36
H.263(384Kbit/s) ≈384 10 6 6.2

注:采用某种编码方式时,用64K乘以相应的带宽系数就可以得出其实际占用的带宽。当然如果是中继接口,还需要考虑信令占据一定的带宽,一般按照2.5%来计算。