Bug Report Bug on FFmpeg UDP output with pkt_size option

[DVBInside]

If you want to feed some UDP players, you need to send 1316 bytes lenght packets (highest 7xTS below usual MTU=1500). This is very easy to try, just adding the option "pkt_size" in your UDP url, this way udp://192.168.1.43:12345?pkt_size=1316. However once I did it, I had a wrong response on my UDP player. I then focused the UDP stream to a Linux box and observed the input with tcpdump (tcpdump -i eth0 udp port 12345). Voilá, here is the bug:

14:09:48.607277 IP 192.168.1.64.57226 > 192.168.1.43.12345: UDP, length 1316
14:09:48.607389 IP 192.168.1.64.57226 > 192.168.1.43.12345: UDP, length 1316
14:09:48.607500 IP 192.168.1.64.57226 > 192.168.1.43.12345: UDP, length 1316
14:09:48.607712 IP 192.168.1.64.57226 > 192.168.1.43.12345: UDP, length 1316
14:09:48.608076 IP 192.168.1.64.57226 > 192.168.1.43.12345: UDP, length 1316
14:09:48.608181 IP 192.168.1.64.57226 > 192.168.1.43.12345: UDP, length 1316
14:09:48.608369 IP 192.168.1.64.57226 > 192.168.1.43.12345: UDP, length 564
14:09:48.608640 IP 192.168.1.64.57226 > 192.168.1.43.12345: UDP, length 1316
14:09:48.608860 IP 192.168.1.64.57226 > 192.168.1.43.12345: UDP, length 1316
14:09:48.609026 IP 192.168.1.64.57226 > 192.168.1.43.12345: UDP, length 376
14:09:48.757985 IP 192.168.1.64.57226 > 192.168.1.43.12345: UDP, length 1316
14:09:48.758251 IP 192.168.1.64.57226 > 192.168.1.43.12345: UDP, length 1316
14:09:48.758253 IP 192.168.1.64.57226 > 192.168.1.43.12345: UDP, length 752
14:09:48.758393 IP 192.168.1.64.57226 > 192.168.1.43.12345: UDP, length 1316
14:09:48.758629 IP 192.168.1.64.57226 > 192.168.1.43.12345: UDP, length 1316
14:09:48.758683 IP 192.168.1.64.57226 > 192.168.1.43.12345: UDP, length 940

Not all packets were completed to 1316 bytes. It is an issue at FFMPEG (even latest git) at libavformat/aviobuf.c#241 .
If you just change line 241 by this new one at https://github.com/vidanio/FFmpeg/commit/860098efada8ea55bfb81cf1ac872c639e290580 , all UDP packets will be filled to the end and my UDP player will be happy :-)

I didn't find another way to submit this bug, but here I drop it to whoever is concerned.
Thanks for this great program.
Regards.

 

[DVBInside]

I have seen that this can be achieved on ffmpeg using the format option "-flush_packets 0" this way

ffmpeg -re -i 576i50.ts -c copy -flush_packets 0 -f mpegts udp://192.168.1.43:12345?pkt_size=1316

However where can I send this format option, and others like -fflags +nobuffer ???

I tried on muxer settings, but gives an error and cannot stream.

Thanks.