[vlc-devel] [PATCH 3/3] access/udp: reduce mtu amount on initial packets

Ilkka Ollakka ileoo at videolan.org
Tue Oct 16 15:28:08 CEST 2018

On Tue, Oct 16, 2018 at 03:00:32PM +0200, Francois Cartegnie wrote:
> Le 16/10/2018 à 14:46, Ilkka Ollakka a écrit :
> > On Mon, Oct 15, 2018 at 10:40:14PM +0200, Francois Cartegnie wrote:
> >> Le 15/10/2018 à 20:30, Ilkka Ollakka a écrit :
> >>> In this approach, mtu is setted to high on start, and if received data
> >>> is less than 1500 and mtu is higher than that, we adjust mtu on future
> >>> packets to be smaller. In majority of cases in UDP streaming, packet
> >>> size is usually quite constant, so it should work, even if it's not
> >>> generic solution to udp packet receiving.
> >> That can't work on a single packet.
> >>
> >> H264 RTP treaming usually sees packets for PPS, SPS, and the remainder
> >> of frames being < MTU.
> > 
> > Would you happen to have tcpdump capture of such case?
> > 
> You don't need. Your patch just should not rely on a single packet, or
> we'll get a randomly reproducible and unfixed bug.

Like mentioned previously, this patch doesn't touch the RTP receiving
side of things. If you have case where plain udp access gets highly
variable size packets that breaks up, then I'm interested to hear about

But if you think I don't need the capture or RTP case is unresolvable by
nature without using really high buffers, then we are stuck and we
should focus on other things.

Ilkka Ollakka

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