webrtc - 冰候选中的组件 ID

Question

典型的SDP消息

v=0
o=- 3376022867449415700 2 IN IP4 127.0.0.1
s=Doubango Telecom - chrome
t=0 0
a=group:BUNDLE audio video
a=msid-semantic: WMS Jyup2XWPA5tOgvau9NIBMjlZFQzSEl6g3P0b
m=audio 57008 UDP/TLS/RTP/SAVPF 111 103 104 9 0 8 106 105 13 126
c=IN IP4 202.53.167.164
a=rtcp:57008 IN IP4 202.53.167.164
a=candidate:2068563606 1 udp 2122194687 192.168.10.148 57008 typ host  generation 0
a=candidate:2068563606 2 udp 2122194687 192.168.10.148 57008 typ host generation 0
a=candidate:902314598 1 tcp 1518214911 192.168.10.148 0 typ host tcptype active generation 0
a=candidate:902314598 2 tcp 1518214911 192.168.10.148 0 typ host tcptype active generation 0
a=candidate:3083270405 1 udp 1685987071 202.53.167.164 57008 typ srflx raddr 192.168.10.148 rport 57008 generation 0
a=candidate:3083270405 2 udp 1685987071 202.53.167.164 57008 typ srflx raddr 192.168.10.148 rport 57008 generation 0
a=ice-ufrag:cinBWZB6tiSnOnf1
a=ice-pwd:50yVBGm5WuKlbZeyRrmjOvMn
a=ice-options:google-ice
a=fingerprint:sha-256 7C:69:84:B5:D5:C1:86:D0:56:8F:22:BA:5F:61:AD:1E:55:21:5A:6A:50:35:0C:49:E2:43:E9:C0:03:CC:B5:31

任何候选优先级取决于典型偏好、本地偏好和组件 ID(引用 RFC 5245)

对于RTP组件id是1，对于RTCP组件id是2

因此，根据组件 ID，候选者的优先级会发生变化。

但是在上面的代码示例中，为什么不同组件 ID 和相同类型候选者的优先级相同。

Answer 1

引自[RFC5245][1]

An agent SHOULD compute this priority using the formula inSection 4.1.2.1

注意“应该”这个词。让我们从 [RFC2119][2] 中了解这意味着什么

SHOULD This word, or the adjective "RECOMMENDED", mean that theremay exist valid reasons in particular circumstances to ignore aparticular item, but the full implications must be understood andcarefully weighed before choosing a different course.

这意味着完全没有必要严格遵循算法来计算候选人的优先级。如果需要，可以修改算法。我认为你提供的SDP就是这种情况。在计算优先级时，他们忽略了候选组件的 ID。[1]:https://www.rfc-editor.org/rfc/rfc5245#section-4.1.2[2]:https://www.rfc-editor.org/rfc/rfc2119