On Thu, Jan 12, 2012 at 09:08:16AM -0800, Eric Carmichel wrote: > Because some of my experiments involve adaptive test procedures, something > has > to 'give' during the test (during = the real-time part). The wav files, > however, do NOT undergo processing once they've been lined up to play in a > particular sequence > via a multi-track device or DAW. An example of an adpative procedure > would be trying to 'force' a speech comprehension score of 50 percent > correct, and altering the SNR to achieve this score. The background > noise level, signal level, or both would have to change in 'real time' > (that is, change while the test is in progress) to zero in on the SNR > that yields a 50 percent speech score, subject by subject. Background noise > is continuous and on its own tracks, while the speech stimuli is lined up > sequentially on a separate track or tracks.The background noise plays through > x number of speakers at a time (let x = 6 for horizontal-only Ambisonic > surround) while the speech plays > through a dedicated speaker or speakers, but always one at a time. If I want > the speech signal to be > maintained at, for example, 75 dB SPL and the listener isn't having > difficulty with the speech material at + 5 dB SNR, then the background level > (all six > channels) has to be elevated as the test moves forward. All I really need to > do is automate the levels, not process the wav > files from B-format to speaker feeds. To change the background noise > level (presented through 6 speakers) means that all six channels have to > change in unison and precisely by the same amount, perhaps in 2 dB > steps. This is pretty straightforward with a discrete, 6-channel preamp. With > a DAW, as you know, controlling six channels simultaneously > requires sending them to a buss with a minimum of six channels (a 7.1 > surround buss works nicely--just don't panpot anything and keep the > channels totally discrete). The surround buss's master fader can adjust > all channels simultaneously, and I do this in 'real-time' based listener > responses. Actually, responses are recorded, and my software/hardware > combo does the fader adjustment automatically.
Provided the test person uses the PC keyboard or mouse, or the interface he/she uses can be interfaced (e.g. a LaunchPad - a 9 by 9 matrix of variable color LED illuminated pushbuttons) all of this and more can be done quite easily in Linux by using some Python (high level interpreted language) code to control the Ardour DAW. Ardour has no artificial limits on the number of tracks or busses, the number of channels in a bus or track, and how you interconnect things. Transport and fader gains can be controlled remotely via OSC (Open Sound Control) messages. Creating automated systems is quite easy once you've got the basic infrastructure set up, which is little more than a number of Python classes allowing 'application level' programming. I'm doing this routinely for 'live electronics' in contemporary music concerts and production. Ciao, -- FA _______________________________________________ Sursound mailing list [email protected] https://mail.music.vt.edu/mailman/listinfo/sursound
