[vlc-devel] Streaming MRL issue: MRL incorrectly created via GUI?

Claudio Allocchio Claudio.Allocchio at garr.it
Mon Dec 14 16:52:58 CET 2009

Hash: SHA1

Hello all,

VLC has always been the "preferred" tool used by a large community in 
order to receive and display the good and high quality streamed generated
by DVTS and HDVTS encoders ( http://www.sfc.wide.ad.jp/DVTS/ ) both in 
unicast and multicast mode.

Since VLC v1.0 was out, both for OSX and XP platforms, we detected a 
problem in VLC when it generates the streaming MRL using its embedded 
GUI; the problem makes users think of something related to the streaming 
itself. On the other end, the problem does not exist if the MRL is entered 
manually. Thus it is simply a badly automatically generated MRL from the 

Here are the details for OSX (see below for XP).

In OSX versions 1.0.1, 1.0.2 and 1.0.3 (pretty the same) after "Open 
Network..." the only way to enter the correct MRL is by opening the Media 
Resource Locator (MRL) tag explicitly, and type in the correct complete 
value, for example


whichever other combination entered via the GUI (selecting "Open RTP/UDP 
Stream" button and filling in the GUI form) produces the wrong MRL

   RTP Multicast IP Address Port 1234
     produces the MRL rtp://@   ! ":1234" is missing !

   UDP Multicast IP Address Port 1234
     produces the MRL udp://@   ! ":1234" is missing !

NOTE: without the ":1234" VLC does not join correctly the multicast 
stream, even if "1234" is the default port. It seems that ":1234" must be 
present in any case explicitly in the MRL, but the GUI does not generate 
it. If the port is any different number, then the GUI correctly adds it.

For Unicast the complete correct URL is: rtp://@:port and udp://@:port. 
The GUI generates:

   RTP Unicast Port 1234
     produces the MRL rtp://   ! "@:1234" is missing !

   UDP Unicast Port 1234
     produces the MRL udp://   ! "@:1234" is missing !

NOTE: without the "@:1234" VLC does not start receiving correctly the 
stream if RTP is used. On the other hand, if UPD is used, then VLC 
received correctly ALSO without the "@:1234" in the MRL. If the port is 
different from "1234", then the GUI generates correct complete MRLs.

Windows XP version, UNICAST:

VLC any version:

The default "Open network stream..." menu does not work both with udp and
rtp protocols selected, unless you insert as network address, in 
order to create the MRL




e.g. the unicast receiving stream ONLY works if a IP address is 
added to the MRL.

In order to reproduce this, you just need the following:

  - connect an HDV camera to HDVTS (best if you use the Windows XP version)
    and start streaming whichever you like either in multicast or unicast;

  - use VLC to try to receive the stream (multicast or unicast)

IF, as it looks like, this is a buggy imolementation of the latest VLC 
"Open Network..." MRL generator via the GUI, I guess it should be fixed 
ASAP. user's are not able to distiguish these subtle differences in MRLs, 
and get confused, resulting unable to receive streams.

thanks... and best regards

PS: there is yet another interaction issue between HDVTS and VLC, but I'll 
post it in a separate e-mail.

- ------------------------------------------------------------------------------
Claudio Allocchio             G   A   R   R          Claudio.Allocchio at garr.it
                         Senior Technical Officer
tel: +39 040 3758523      Italian Academic and       G=Claudio; S=Allocchio;
fax: +39 040 3758565        Research Network         P=garr; A=garr; C=it;

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