[linux-audio-dev] best option for audiovisual synchrony

[Frank Barknecht]

Hallo,
Simon Barthelmé hat gesagt: // Simon Barthelmé wrote:

> Concretely speaking, that means we need to get as precise a timing and 
> synchrony as  we can possibly get.  A typical experiment will go 
> something like this :
> - display a flash and, at the same time, play a beep
> - wait for response
> 
> The tricky bit is of course getting a flash that's totally synchronous 
> with the beep. Absolute synchrony is not achievable without dedicated 
> hardware, but we need to get an approximation that's within the few ms 
> range.

Pure Data (Pd)  with one of its video extensions like Gem can tightly
sync audio and video. The usual framerate of Gem is 20fps, but you can
tune that. You can access the triggering of every frame to trigger a
sound immediatly. 

You can also use Pd to collect back the reaction of a human to this
using for example Pd's [hid] objects to acces HID devices. This
hid-input however seems to have a bit more latency. If you search the
archives of the Pd mailing list, you should find a longer thread
regarding this from some weeks ago, where somebody was actually using
Pd this way in psychological research. Maybe these experiences are
useful to you as well.

Ciao
-- 
 Frank Barknecht                 _ ______footils.org_ __goto10.org__