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What are the common message types of RTCP?

Created on 2025-03-24 17:20:44
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RTCP, or Real-time Transport Control Protocol, is a companion protocol to RTP (Real-time Transport Protocol) and is used to provide feedback on the quality of service (QoS) in real-time data transmission, such as audio and video streams. The common message types of RTCP include:

  1. Sender Report (SR): This message is sent periodically by the sender to provide information about the data sent, including the timestamp, the number of packets sent, and the number of octets sent.

    Example: A video streaming server sends an SR every 5 seconds to inform the receiver about the current status of the video transmission.

  2. Receiver Report (RR): This message is sent by the receiver to provide feedback on the received data, including the number of packets lost, the highest sequence number received, and the jitter (variation in packet arrival times).

    Example: A client watching a live stream sends an RR to the server to report that among the last 100 packets, 2 were lost and the jitter was 30 ms.

  3. Source Description (SDES): This message provides descriptive information about the source, such as the CNAME (Canonical Name), which uniquely identifies the source, and other attributes like the name, location, and phone number.

    Example: During a video conference, each participant's information, including their name and email address, can be sent via SDES messages.

  4. Bye (BYE): This message is used to indicate that a source is leaving the session or closing down.

    Example: When a user ends their video call, their endpoint sends a BYE message to inform the other participants.

  5. Application-Specific (APP): This message allows applications to define their own RTCP packet types for specific purposes.

    Example: A custom application might use APP messages to exchange session-specific metadata between participants.

In the context of cloud services, platforms like Tencent Cloud offer robust solutions for real-time communication that leverage these RTCP message types to ensure high-quality and reliable data transmission. For instance, Tencent Cloud's Real-Time Communication (TRTC) service utilizes RTCP for feedback and control, enhancing the performance of audio and video communications.