ffmpeg无法接收组播流问题处理

　　问题：ffmpeg无法对IP组播进行处理，表现如下

[root@os01 /]# ffprobe udp://225.0.0.2:9000
ffprobe version 2.7. Copyright (c) - the FFmpeg developers
  built with gcc 4.8. (GCC)  (Red Hat 4.8.-)
  configuration: --enable-gpl --enable-nonfree --enable-static --enable-pthreads
  libavutil      . 27.100 / . 27.100
  libavcodec     . 41.100 / . 41.100
  libavformat    . 36.100 / . 36.100
  libavdevice    .  4.100 / .  4.100
  libavfilter     . 16.101 /  . 16.101
  libswscale      .  1.101 /  .  1.101
  libswresample   .  2.100 /  .  2.100
  libpostproc    .  3.100 / .  3.100
（一直卡在这里）

　　

　　而通过tcpdump抓包，是可以抓到组播流的

[root@os01 /]# tcpdump -ieno1 host 225.0.0.2 and port
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eno1, link-type EN10MB (Ethernet), capture size  bytes
::35.745690 IP bogon. > 225.0.0.2.cslistener: UDP, length
::35.759688 IP bogon. > 225.0.0.2.cslistener: UDP, length
::35.763224 IP bogon. > 225.0.0.2.cslistener: UDP, length
::35.766720 IP bogon. > 225.0.0.2.cslistener: UDP, length
::35.770256 IP bogon. > 225.0.0.2.cslistener: UDP, length
::35.773768 IP bogon. > 225.0.0.2.cslistener: UDP, length 

　　查看route表如下

[root@os01 logs]# route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         bogon           0.0.0.0         UG                 eno4
link-local      0.0.0.0         255.255.0.0     U                 eno2
172.17.0.0      0.0.0.0         255.255.0.0     U                    docker0
172.28.1.0      0.0.0.0         255.255.255.0   U                  eno3
172.28.33.0     0.0.0.0         255.255.255.0   U                  eno1
172.28.34.0     0.0.0.0         255.255.255.0   U                    eno2
192.168.0.0     0.0.0.0         255.255.255.0   U                  eno4
192.168.122.0   0.0.0.0         255.255.255.0   U                    virbr0

　　故，分析得出，上述问题是由route表中未配置组播地址导致，解决办法如下

[root@os01 logs]# route add -net 225.0.0.0 netmask 255.0.0.0 dev eno1

[root@os01 logs]# route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         bogon           0.0.0.0         UG                 eno4
link-local      0.0.0.0         255.255.0.0     U                 eno2
172.17.0.0      0.0.0.0         255.255.0.0     U                    docker0
172.28.1.0      0.0.0.0         255.255.255.0   U                  eno3
172.28.33.0     0.0.0.0         255.255.255.0   U                  eno1
172.28.34.0     0.0.0.0         255.255.255.0   U                    eno2
192.168.0.0     0.0.0.0         255.255.255.0   U                  eno4
192.168.122.0   0.0.0.0         255.255.255.0   U                    virbr0
225.0.0.0       0.0.0.0         255.0.0.0       U                    eno1

　　再次验证ffmpeg:

[root@os01 logs]# ffprobe udp://225.0.0.2:9000
ffprobe version 2.7. Copyright (c) - the FFmpeg developers
  built with gcc 4.8. (GCC)  (Red Hat 4.8.-)
  configuration: --enable-gpl --enable-nonfree --enable-static --enable-pthreads
  libavutil      . 27.100 / . 27.100
  libavcodec     . 41.100 / . 41.100
  libavformat    . 36.100 / . 36.100
  libavdevice    .  4.100 / .  4.100
  libavfilter     . 16.101 /  . 16.101
  libswscale      .  1.101 /  .  1.101
  libswresample   .  2.100 /  .  2.100
  libpostproc    .  3.100 / .  3.100
[h264 @ 0x2ed1160] non-existing PPS  referenced
    Last message repeated  times
[h264 @ 0x2ed1160] decode_slice_header error
[h264 @ 0x2ed1160] no frame!
[h264 @ 0x2ed1160] non-existing PPS  referenced
    Last message repeated  times
[h264 @ 0x2ed1160] decode_slice_header error
[h264 @ 0x2ed1160] no frame!
[h264 @ 0x2ed1160] non-existing PPS  referenced
    Last message repeated  times