Matlab audiocapture5/17/2023 ![]() ![]() ![]() Jump to section DAC & DSP for more specific Mathematica related discussion. NeuroDebian now ships one from May 2016.I want to identify resources and strategies to implement a Mathematica based solution for audio digital signal processing (DSP) and digital to analog conversion (DAC). your Psychtoolbox seems to be slightly out of date. Visual stimulus onset time stamping on the Intel Sandybridge graphics card should also be excellent, so the only thing that could ruin your timing would be use of a slow flat panel display instead of, e.g., a CRT monitor or a fast flat panel display.ītw. That said, as you are using Linux, if you use a typical built in Intel HDA onboard soundchip, so far the accuracy of the audio timestamping was always better than <= 1 msec on tested systems in the past. In general you should always test the accuracy of the audio time stamping via some independent method once, as one can never know if there aren't any hardware bugs somewhere. However, that demo does not use low latency / high timing precision mode as one should use for this, because voice onset timestamping is only a bonus feature in that demo and the basic demo was also supposed to work on deficient Microsoft Windows systems, hence that little sacrifice of timing accuracy. ReactionTime = tResponse - tVisualOnsetīasicSoundInputDemo (, 0.1) shows this in a similar way, except a bit more sophisticated. tResponse = tCaptureStart + (n / freq) Ħ. Get the captured audio via 'GetAudioData' and find voice onset sample n.ĥ. Wait for the duration of the response period, then stop audio capture.Ĥ. Whenever you like = Screen('Flip') the stimulus onscreen.ģ. Then, given the selected audio sampling rate 'freq', once you found the location 'n' of the first sample of the voice response in the audio sample vector returned by PsychPortAudio('GetAudioData') you can translate that into the voice response onset time as:Ģ. TCaptureStart = PsychPortAudio('Start', pahandle, 0, 0, 1) > You can get the start time of recording from: Would it be enough to trust the inconsistent (but known after the fact) offset between recording and visual presentation, and to account for that offset when measuring the latency of the speech response? It doesn't matter if the recording starts synchronously with the visual stimulus, as long as there is a consistent, known offset that we can use to correct the latency estimates. Processor: Intel® Core™ i5-2540M CPU 2.60GHz × 4ģ.0.12 - Flavor: Debian package - psychtoolbox-3įor each trial in our experiment, we want to display a visual stimulus and record speech audio, and measure the latency of the speech response with respect to the visual stimulus. PsychPortAudio('Start') does not allow precise control of in pure Interval? We want to be able to schedule the visual stimulus for aįixed delay after the start of audio capture (which How do we get around the delays introduced by the refresh rate Probably not coincidentally, this is the same refresh interval Which was generated by the above script). Off from the 'when' argument by up to 16.8 ms (see attached figure, Measured by VBLtimestamp, StimulusOnsetTime, or FlipTimeStamp, was To Screen('Flip'), with some jitter added between stimuli: ![]() Time and scheduling a flip for 100ms later using the 'when' argument This script presents visual stimuli by getting the current We made a simpler script to examine this issueįurther. Visual stimulus presentation as defined by the output arguments to Noticed a variable discrepancy between the start of recording and We used the 'when' argument in Screen('Flip') to do this, but we Time after the reported start time of audio capture. PsychPortAudio('Start') doesn't allow you to schedule the start ofĪudio capture, we scheduled the visual stimulus to appear at a set We are trying to schedule a visual stimulus for a set time after weīegin audio capture for an experiment. ![]()
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