srt live transmit UDP buffer size config

[maxsharabayko]

Added the possibility to set the buffer size of the UDP socket.

It turned out at high and bursty data rates (~60 Mbps) the epoll_wait(udp_socket) is not fast enough to signal about the possibility to read from a socket. It results in loosing data when there

Waiting on a UDP socket with ::select(...) works perfect, but we can't use it in the current implementation of the srt-live-transmit.

UDP socket needs a bigger buffer to store incomming data. For example, setting 64 MB buffer seems to workaround the issue #933.

Increase the system-default max rcv buffer size

$ cat /proc/sys/net/core/rmem_max
212992
$ sudo sysctl -w net.core.rmem_max=26214400
net.core.rmem_max = 26214400
$ cat /proc/sys/net/core/rmem_max
26214400

Specify the size of the UDP socket buffer via the URI

Example URI:

"udp://:4200?rcvbuf=67108864"

Example full URI:

./srt-live-transmit "udp://:4200?rcvbuf=67108864" srt://192.168.0.10:4200 -v

TODO

• Remove verbose messages regarding the size of the buffer

[maxsharabayko]

Ran the experiment for 2 minutes. No losses on the UDP socket when streaming 60 Mbps with the timing taken from #933 (udp-mcast-60mbps-timing.zip).

The following pipeline was used:

./srt-live-transmit "udp://:4200?rcvbuf=67108864" srt://192.168.0.10:4200 -v

13:10:11.393867 [I] VALIDATOR Overal pkts received: 1, lost: 0
...
13:12:11.211656 [I] VALIDATOR Overal pkts received: 682557, lost: 0