note to me

docker compose build --network host

docker compose up -d --force-recreate

TODO

let user choose whether use mirror (use which mirror) when building Dockerfile

Based on the logs and the GB/T 28181-2022 standard you provided, here is the explanation:

Yes, this is SIP, but the content inside the SIP message is SDP (Session Description Protocol).

While XML is used for control (like PTZ), SDP is used for Media Negotiation (setting up the video stream).

The Architecture from your logs

SIP (The Envelope): Starts the conversation ("I want to watch video").
SDP (The Letter inside): Describes technical details ("Send video to IP X, Port Y, using Format Z").
RTP (The result): After this SIP/SDP handshake finishes, the actual binary video stream (PS/H.264) starts flowing over a separate TCP/UDP connection.

Breakdown of your Log

This log shows a Real-time Live View handshake.

1. The Request (SRS Server -> Camera)

The Server asks the Camera to send video.

INVITE sip:34020000001320000001@3402000000 SIP/2.0
Content-Type: application/sdp

s=Play                         # "Play" = Real-time Live View (Standard 9.2.2.1)
c=IN IP4 192.168.2.184         # The Media Server IP
m=video 9000 TCP/RTP/AVP 96    # "Send video to my Port 9000 via TCP"
a=recvonly                     # "I will only receive, not send"
y=0911024252                   # **GB/T 28181 Special**: The SSRC (Stream ID)

2. The Response (Camera -> SRS Server)

The Camera agrees and tells the server its own details.

SIP/2.0 200 OK
Content-Type: application/sdp

c=IN IP4 192.168.2.64          # The Camera IP
m=video 15060 TCP/RTP/AVP 96   # "I am sending from Port 15060"
a=sendonly                     # "I will only send"
a=setup:active                 # "I will initiate the TCP connection to you"
y=0911024252                   # Matches the SSRC provided
f=v/2/2560x1440/25/2/8192a/... # **GB/T 28181 Special**: Media Info

Key Differences from Standard SDP

GB/T 28181 modifies standard SDP with two specific fields mandatory for this protocol:

y= (SSRC):
- Standard SDP: Does not have a y line.
- GB/T 28181: Uses y to define the SSRC (Synchronization Source). This 10-digit number is crucial because it marks every binary video packet sent later. If the binary stream headers don't match this y value, the stream is rejected.
f= (Media Info):
- Standard SDP: Does not have an f line.
- GB/T 28181: Uses f to describe video parameters. In your log: v/2/2560x1440/25... means:
  - v: Video
  - 2: Coding format (likely H.264 or H.265 mapped)
  - 2560x1440: Resolution
  - 25: Frame rate

Summary of Cooperation

XML (SIP MESSAGE): Used for "remote control" (PTZ, Query, Keepalive).
SDP (SIP INVITE): Used to negotiate the pipeline.
Binary (RTP/PS): The actual heavy video data that flows through the pipe created by the SDP.

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