The High Fidelity team seem to be having such a good time, having a ball and whereas they may not be quite travelling at the speed of light, the team are working at reducing the curse of latency, as they explain in their blog post : Measuring The Speed Of Sound.
We are obsessed with reducing latency, because we have observed aspects of 1:1 interaction which are broken by too much latency.
The issue that seems to be causing most concern is that of audio, rather than video. I’d really like to know what the mobile phone has ever done to Philip Rosedale. Did he have a hot tip on the horses that he received too late to place a bet on because of latency? There’s more to this than meets the eye, or in this case, ear.
However back to the technology. The High Fidelity team conducted a test, as they explain in their blog post :
We connect two high quality microphones directly to the two input channels of a digital oscilloscope, and we then use either a metronome or simply snapping our fingers or clapping to create a sharp audio signal that can be detected by both microphones. By positioning one microphone at the input of an audio system and the other at the output, we can then easily and reliably use the scope to capture the delay over multiple samples down to millisecond resolution.
The results of the test were interesting, Skype winning the day over mobile phones. However with regards to mobile phones themselves, it seems Verizon are quite a bit more efficient than AT&T or T-Mobile if you’re making your call in the San Francisco area. Verizon’s measured 280msecs for 1-way latency, compared to 400-450msecs for AT&T and T-Mobile.
Skype blew them all away however, in terms of end to end latency, as the blog post explains :
Skype, by comparison, generally outperforms the cell phones in terms of end-to-end latency: we measured audio delays of from 100-200msecs for various combinations of audio and video calls, where the two endpoints were on the same WiFi network. So this means that with a packet delay of about 40 msecs (which is what we typically see when pinging Boston from San Francisco), a cross-country audio or even video call on Skype is going to come in with about 250msecs of delay and be a bit better than using a cell phone.
Pretty impressive results, but far from good enough for the ambitions of the High Fidelity team.
The blog post gets on to the future and the latency aims get pretty damn impressive :
On our own internal work on shared audio for High Fidelity, we’ve been able to get the audio delay down to about 75-90 msecs. We’ve also tested the experience quality of different amounts of audio delay, and found that less than 50 milliseconds is the point where when hearing one’s own voice the delay becomes imperceptible, and at less than 125 milliseconds or so the difference between the audio and video feeds of another person speaking usually becomes indistinguishable.
Now realistically, there are always going to be latency issues in a global virtual world, this is inevitable. Managing that level of latency is always going to be a challenge and there are a number of hurdles involved there. The High Fidelity team appear to be very keen to reduce the impact and that aim is very noble. Time will tell (no pun intended) whether their aims can be realised to a degree that makes people sit up and take notice.
Obviously many people will be hoping that in High Fidelity they will be a shooting star leaping through the skies, Like a tiger defying the laws of gravity. I’m sure defying the laws of gravity will be possible at the very least.
High Fidelity is still very much in the alpha phase and I’ll say again that people should take a step back and not expect to see a fully polished product at this moment in time. However the concepts they are experimenting with are, to me at least, rather fascinating and I’m very interested in seeing how this all progresses.
“we measured audio delays of from 100-200msecs for various combinations of audio and video calls, where the two endpoints were on the same WiFi network.”
The same tests by High Fidelity being done on the same Wi-Fi network and achieving a 75ms delay seems impressive until you scale that up and realize you’re back to square one when you account for packet switching and actual real world Internet congestion.
Effectively High Fidelity are touting that they’ve lowered latency impressively just so long as you don’t attempt to apply it to a real world situation.
Absolutely, I think their aim is to try and improve speeds so that they can outperform Skype but they are going to run into bottlenecks beyond their control as the communications go further afield.