[vlc-devel] Multiple Instances of access-udp module?

Jean-Paul Saman jean-paul.saman at planet.nl
Sat Nov 17 14:38:54 CET 2007

Bill Dolson wrote:
> Hi,
> I have been working for several months extending VLC to include support 
> for private_data_1 streams carrying camera geopositioning and pointing 
> data encoded as SMPTE KLV.  This is an emerging standard for many forms 
> of remote sensing from satellite to autonomous vehicles.  I will start 
> to submit patches when the work is a little further along.
> I am currently working on muxing together a data stream and video stream 
> from two different sources.  I am using the input-slave control and have 
> added a slave-demux control to allow forcing my demuxer for the data 
> stream.  In testing this I set up each source as a UDP stream and the 
> access-udp module is used for each, hence two instances.  (All on a 
> UDP-safe LAN of course).  After some 15 seconds or so I start to get 
> massive amounts of continuity counter errors on the video stream 
> (typically 4-6 counts off), as if many packets were being dropped.  If I 
> disable the access-udp which is reading the data stream everything is 
> fine.  I suspect the two instances are somehow interfering with each other.
> Is there any reason why running two instances of access-udp should be a 
> problem?  I took a quick look at the source and don't see anything 
> obvious.  I am unhappy to report development is being done under Windows 
> XP with the 0.8.6b sources (not my decision).  I have periodically tried 
> the Windows nightlies and they don't seem to be all there yet. 
> Obviously when I submit patches I will apply them to the current SVN.
What are the bitrates of the two streams? In my experience these packet 
drops can be caused by overflowing the OS's its network buffers. From 
you description this could be the case here. Under Linux you could test 
this by increasing the receive buffer of the network stack, but I don't 
know if that can be tweaked under win XP too.

Jean-Paul Saman.

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