[AG-TECH] Better use of bandwidth in the AG

[George Estes]

Thanks Jason!

----- Original Message -----
From: "Jason Bell" <j.bell at cqu.edu.au>
To: "George Estes" <gestes at ncsa.uiuc.edu>, ag-tech at mcs.anl.gov
Sent: Thursday, February 5, 2009 5:52:45 PM GMT -06:00 US/Canada Central
Subject: RE: [AG-TECH] Better use of bandwidth in the AG

George

Having had low bandwidth issues in the past, the following might be useful:

*	Rat has many codec's, for example, using the default "linear-16" uses around 256k per stream..  Whereas using something like GSM will drop the rate down to something like 4-10k.  The main reason why I use the default is I have had issues in the past (a few years ago), where I used GSM and other sites were unable to decode that codec...  This may (haven't tested it) be an issue when connecting to iocom, or evo bridges as the other software cannot decode various codec's that rat can.  Note that when I was testing using GSM, the audio quality was slightly better, but because bandwidth is not an issue for me, I stick to using "linear-16" for usability reasons.

  This is good info.  With the low-rate codecs I've tried the audio quality really dropped off.
I'll give the GSM codec a try.


*	Obviously things like using one video stream will save bandwidth (think about saving multiple configurations, which then allows you to easily select the best config for various situations).  But there are other things you can do to assist in reducing video bandwidth.  Generally speaking within the Access Grid, particularly vic, the h261 codec transmits the lowest bandwidth (which is configurable, i.e., set to transmit a max of 250k at 10fps [dropping the quality setting drops the bandwidth]), but because the h261 codec works by transmitting changes (i.e. movement) could can also help by reducing movement from the capture area..  Example:

*	Remove moving blinds, and objects;
*	improve background by fixing curtains, changing background wall colour etc. If the camera "hunts" for focus, this will cause the bandwidth to increase;

  All good points!  And all of these things I've used.  But of course some of these things only work when you have strict control over the event.

Unfortunately there doesn't appear to be good quality, low bandwidth solution for video, but remember it is possible for sites to just connect using audio and use something like VNC to view presentations, or you might consider some sites transmitting no video where it isn't important.

  This what some of our users are doing, using a web conference application that is just audio with a shared document feature.  But then if they're satisfied with that then they no longer need the Access Grid.

Also, you might be interested to have a look at the "VB Multicast Bridge" and "VX".  Those these projects are not fully developed (Haven't really tested) and no longer developed, they might interest you.  See http://www.accessgrid.org/projects.

  I'll take a look.
Thanks again,
George

Anyway, I hope you find some of this information useful.

Many regards,
Jason.

-----Original Message-----
From: George Estes [mailto:gestes at ncsa.uiuc.edu] 
Sent: Friday, 6 February 2009 03:26 AM
To: ag-tech mailing list
Subject: [AG-TECH] Better use of bandwidth in the AG

Hello,

  Is anyone out there looking at video and audio codecs that use less bandwidth than the current AG codecs?
I know it's not as glamorous a topic as HD codecs but there's a large potential AG community out there that only has maybe a T1 connection.
  One of our PI's has expressed interest in providing some funds toward developing a "low bandwidth AG".

Thanks,
George