[hackerspaces] Looking for another hackerspace to share telepresence

Bob Baddeley hackerspace-discuss at bobbaddeley.com
Thu Jan 19 18:31:35 CET 2012

I implemented this at a former job using completely open source tools 
and off-the-shelf components: ( http://vimeo.com/25094355)

We used vlc to encode the video from an HD webcam and display it on the 
other end. We had the audio in a separate vlc stream. There was a web 
server with some simple web services that maintained the list of rooms 
and which IP+port each connection was on. It was still P2P, with the web 
services acting as a mediator. The awesome part was having a shared 
partially transparent desktop that both people could interact with.

Some lessons learned:

1) We had to go through a lot of hoops to get the latency as low as 
possible. Even a couple tenths of a second is annoying enough to make 
the system practically useless. Bandwidth can be cranked down quite a 
bit until you have barely recognizable blocky video, but it's still 
useful as long as the latency is low.

2) Because the latency was so low, any jitter would freak out VLC, so we 
had to have a process that watched VLC and restarted it if anything went 
wrong. The UI also had a way to reconnect the feeds.

3) We did have issues with networks that couldn't open a port and 
forward it to our systems. I imagine that wouldn't be so much of a 
problem here where we have more control over our networks.

4) Ubuntu+Compiz is pretty awesome for being able to write rules for 
making windows maximized, forced in front, and partially transparent. 
Windows and Mac couldn't even come close to accomplishing it.

5) Video telepresence is cool, but bandwidth heavy and breaks apart 
quickly when there are multiple feeds. That's why we separated the video 
and audio. The audio had lower latency and bandwidth, and it was easy to 
connect to multiple people to get the teleconference effect, but for 
video we settled on being able to see only one of the feeds at a time. 
This had the additional advantage of allowing anyone to participate no 
matter what hardware they had.

6) You NEED noise canceling mic/speaker setups. With any kind of audio 
delay, you have the mic picking up the speaker, and then you get a 
feedback loop that gets out of control. The noise canceling mic/speakers 
solve this.

Bob Baddeley

On 01/19/2012 10:52 AM, Elmar mc.fly Lecher wrote:
> Am 19.01.2012 17:44, schrieb Chris Weiss:
>> On Thu, Jan 19, 2012 at 10:30 AM, Elmar mc.fly Lecher
>> <mc.fly at ramdrive.org>  wrote:
>>> I would propose using chaosvpn for the link between the hackerspaces.
>> telepresence is very latency sensitive, I'm not sure if a VPN would
>> perform well enough for HD video.  VPNs tend to even mess up simple
>> 64Kbps audio.
> The reason why we use tinc is that we use it for VOIP. The ccc voip
> system has been the main user for our network.
> Low latency is also the reason why "full mesh" was one of the design
> principals
> mc.fly ...
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