[vlc-devel] Re: Jumpy streaming multicast UDP: Any help appriciated...

Dermot McGahon dermot at dspsrv.com
Tue Feb 8 11:20:11 CET 2005

On Tue, 08 Feb 2005 08:48:03 +0100, Marius Kjeldahl <marius at kjeldahl.net>  

> Dave Harley wrote:
>> Hi there,
>> I'm  streaming DVD using multicast UDP and its cloppy.  About ever 1/2
>> second I loose a few frames.  The network is fine, the switch is a
>> high end job and there is no packet loss, errors or collisions on
>> either the rx or tx ports.  Below is a sample of the output from vlc
>> with -vvv; can anyone shed any light on this or suggest anything to
>> try?
> I have the identical problem in my home office, and believe it to be the  
>   fault of the swich I am currently using (definitively not "high end").
> Why do I believe this? When I "unicast" the stream over UDP (simply  
> sending the packets over UDP to just the one machine running the vlc  
> client) from the same server as the original multicast came from, it  
> runs just fine. Once I attempt to do the same using multicast, I loose a  
> lot of frames (most, actually, but enough get through to indicate it is  
> trying to listen to the stream).
> I suggest you try the UDP unicast technique to absolutely rule out any  
> network problems. If your network has the right stuff to carry the UDP  
> unicast stream across, it should be able to carry a similar multicast  
> just fine, assuming your switches and similar support it.

Unicast is fine over this network. Multicast is also fine from different
sources. The content is coming from a small h/w encoder box and I suspect
that there is a small mismatch between the content and VLC. If somebody
could have a look at incoming/dump_jumpy.rw I would appreciate it.

It's NTSC DVD connected to a h/w encoder which multicasts MPEG-2 TS/UDP.

In the meantime I'll be reading vout_synchro.c and hoping for inspiration.


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