RTP stream help needed

[fosius]

Hi folks,
I have a problem. I am writing a utility for IPv6 which will be able to determine MTU on path to destination IPv6 node - in case when PMTU protocol fails. After determining MTU to destination this utility allows user to set this MTU to interface which is used to send packets. I wanted to test and prove functionality by VLC RTP stream since this stream is using UDP packets. Problem is that all RTP packets are fixed length - 1390 bytes. When I set MTU on interface manually to 1280 bytes VLC streaming just fails. Is this a bug that VLC is not generating packet with size <= MTU on interface? Or is it possible to set MTU of RTP packets in VLC? I just cannot find any command for this. THANK YOU VERY MUCH

[Rémi Denis-Courmont]

It depends on the payload format, but generally you can set the MTU with the --mtu command line option.

[fosius]

It depends on the payload format, but generally you can set the MTU with the --mtu command line option.

What payload format can I use? Or how can I change it? I tried mtu but did not work.. There is no option to use MTU that is set on network interface? Thanks

[Rémi Denis-Courmont]

Fetching the MTU from the interface is not currently implemented. Almost every format support custom MTU.

[fosius]

Fetching the MTU from the interface is not currently implemented. Almost every format support custom MTU.

Thank you I found it. Although I think VLC should fetch MTU from interface...

[fosius]

Hello again,
I found out that I can change MTU size using vlc.exe --mtu={bytes}. However, when I choose mtu 1330 bytes than VLC is still sending packets bigger than this value (1390 bytes exactly). But when I change mtu to 1300 bytes than VLC is sending smaller packets (1204 bytes). What am I doing wrong?? Please help thank youuu

[Rémi Denis-Courmont]

Border effects due to overhead and packetization constraints.