1）接收者报文内容

RTSP Interleaved Frame, Channel: 0x01, 60 bytes
    Magic: 0x24
    Channel: 0x01
    Length: 60
Real-time Transport Control Protocol (Receiver Report)
    10.. .... = Version: RFC 1889 Version (2)
    ..0. .... = Padding: False
    ...0 0001 = Reception report count: 1
    Packet type: Receiver Report (201)
    Length: 7 (32 bytes)
    Sender ***C: 0xfebeb924 (4273912100)
    Source 1
        Identifier: 0x283e2070 (675160176)
        ***C contents
            Fraction lost: 253 / 256
            Cumulative number of packets lost: -1
        Extended highest sequence number received: 118657
        Interarrival jitter: 1235
        Last SR timestamp: 0 (0x00000000)
        Delay since last SR timestamp: 0 (0 milliseconds)
Real-time Transport Control Protocol (Source description)
    10.. .... = Version: RFC 1889 Version (2)
    ..0. .... = Padding: False
    ...0 0001 = Source count: 1
    Packet type: Source description (202)
    Length: 6 (28 bytes)
    Chunk 1, ***C/CSRC 0xFEBEB924
        Identifier: 0xfebeb924 (4273912100)
        SDES items
            Type: CNAME (user and domain) (1)
            Length: 15
            Text: DESKTOP-KPVK7LH
            Type: END (0)

24 01 00 3c 81 c9 00 07 fe be b9 24 28 3e 20 70
fd ff ff ff 00 01 cf 81 00 00 04 d3 00 00 00 00
00 00 00 00 81 ca 00 06 fe be b9 24 01 0f 44 45
53 4b 54 4f 50 2d 4b 50 56 4b 37 4c 48 00 00 00


2）异常接收报文


RTSP Interleaved Frame, Channel: 0x01, 80 bytes
    Magic: 0x24
    Channel: 0x01
    Length: 80
Real-time Transport Control Protocol (Receiver Report)
    10.. .... = Version: RFC 1889 Version (2)
    ..0. .... = Padding: False
    ...0 0001 = Reception report count: 1
    Packet type: Receiver Report (201)
    Length: 7 (32 bytes)
    Sender ***C: 0xc009d701 (3221870337)
    Source 1
        Identifier: 0xbd7266dd (3178391261)
        ***C contents
            Fraction lost: 0 / 256
            Cumulative number of packets lost: 0
        Extended highest sequence number received: 2175
            Sequence number cycles count: 0
            Highest sequence number received: 2175
        Interarrival jitter: 0
        Last SR timestamp: 0 (0x00000000)
        Delay since last SR timestamp: 0 (0 milliseconds)
Real-time Transport Control Protocol (Source description)
    10.. .... = Version: RFC 1889 Version (2)
    ..0. .... = Padding: False
    ...0 0001 = Source count: 1
    Packet type: Source description (202)
    Length: 11 (48 bytes)
    Chunk 1, ***C/CSRC 0xC009D701
        Identifier: 0xc009d701 (3221870337)
        SDES items
[RTCP frame length check: OK - 80 bytes]



问题1）Length: 7 (32 bytes)该数据是如何计算出来的

如下是一些翻译的解析

长度： 16 比特 该 RTCP 包的长度减 1。其单位是 32 比特字，包括头和任何填充字节。
长度：16位，32位字RTCP包长度的一半。

英文原文

   length: 16 bits
      The length of this RTCP packet in 32-bit words minus one,
      including the header and any padding.  (The offset of one makes
      zero a valid length and avoids a possible infinite loop in
      scanning a compound RTCP packet, while counting 32-bit words
      avoids a validity check for a multiple of 4.)
该RTCP包长度除以4减去1，除以4是以32比特作为单位，所以长度7，换算回来就是(7+1)*4 = 32