Re: [Openh323-devel] sending uncompressed video in OPAL

[Derek Smithies <derek@xxxxxxxxxxxxxx>]

HI,

> It seems to be a sofware performance problem:
> 
> I tried to send a 176*144 RAW RGB video at 5 fps. The network utilisation is
> about 3% with a 100 Mb ethernet card.

An unusable report, I am sorry.
This is Assumption.

I need facts.

Do the numbers first, and report them.
5fps, 176*144, how much data is that ?
How many packets per second should be sent?

Now run the OPAL code in high debug mode.
Is OPAL generating the right number of packets

Are the UDP packets being silently deleted by the network layer of the 
host, as there are so many of them?

> about 3% with a 100 Mb ethernet card.
Measured with?

Key question:
Opal does not seem to be coping with the video - someones report.
This is not something I have tried, so I cannot answer the question.
All I can do is ask the questions that force the people with the gear
setup to answer the question.

Why this failure mode?
 possible answers:
   packets dropped in the network
   cpu speed
   host speed

Well - answer the questions and work it out.

Derek.

 
On Fri, 7 Sep 2007, damd@xxxxxxx wrote:

> 
> Hi,
> 
> It seems to be a sofware performance problem:
> 
> I tried to send a 176*144 RAW RGB video at 5 fps. The network utilisation is
> about 3% with a 100 Mb ethernet card.
> I also tried to connect two PC directly with a gigabit connection with the same
> result.
> Packet size is 1000 bytes.
> 
> I also noticed that the packets that codes the top of a frame are never lost,
> contrary to the rest of the frame.
> 
> Code is attached to this mail.
> 
> regards,
> 
> Damien
> 
> > > I've modified the RFC4175 transcoder in the CVS head in order to send
> > > raw RGB24 images trough SIP.
> >
> > Excellent!
> >
> > > The code is partially working, but generates lost packets (see the
> > > output bitmap for details). Framerate is very slow.
> >
> > Sending uncompressed video over a LAN will require a VERY fast network. A
> > quick calculation for RGB CIF, 25 fps, is 352*288*3*25*8 = 60 MB/s. And that
> > does not include the overhead! Also assuming a maximum 1400 byte packet, we
> > have 5430 packets per second. Now that is going to strain even a 100baseT
> > network, so you will probably get lost packets in the switches and PC
> > stacks.
> >
> > > Is there a way to avoid this situation ?
> >
> > Get a 1G LAN! :-)
> >
> > Also make sure all your RTP packets < 1400 bytes, pushing up toward the MTU
> > also can cause lost packets in some switches/PC stacks.
> >
> >
> >
> > Robert Jongbloed
> > OPAL/OpenH323 Architect and Co-founder.
> >
> >
> >
> >
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> >
> 
> 
> 

-- 
Derek Smithies Ph.D.
IndraNet Technologies Ltd.
Email: derek@xxxxxxxxxxxxxx
ph +64 3 365 6485
Web: http://www.indranet-technologies.com/

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