Re: [LAU] OT - Audio and Video Synch

On 19/10/13 07:23, Len Ovens wrote: a neat thing (mentioned before on this list I think) ... try shifting your gaze to an analogue clock with a second hand that jumps every second and as you do so compare the perceived time before the first tick with the time between the other ticks. Generally the time to the first move seems longer than the others. An explanation for this is that our brains maintain a certain latency between receiving sensations and building a model of the world from the combination of these (presumably for the same reason a computer does, to give time for all the sensations to be received and processed) and that when we shift gaze quickly the model we build is extrapolated back through this latency, including assuming the stationary second hand was stationary through this whole buffering time. I guess it is related to our reaction time, and also related to the importance of the parts of the nervous system that process and respond directly, not going back to the brain at all. On a more speculative level ... I've always noticed that if I burn my hand on a soldering iron I smell the burn before I feel the pain, and I think I actually pull my hand away before being aware of either. Maybe smell is not synced in the same way as vision, touch and sound are?? As far as video and audio sync go ... with a live actor on stage, and a camera on their face with a big screen behind them, in a space where the actor is speaking and maybe 3 metres from the front row, I found that a video system without genlock but using several PCI analogue camera inputs mixed together with openGL gave me between 1/2 and 1 1/2 frames delay, the video lagging behind the live voice and that was just acceptable in context, but quite noticeable, while most other video input systems where impossible (especially firewire!). Simon