SV Mazurka Plugin:
Tapping evaluation of Sonic Visualiser

    Base-line Measurment

    The following two plots are taking from the Even Tapping experiment. The program used to measure the tap timings was a console application for Windows.

    Timing values are measured indirectly via the CPU clock cycle counter. Thus the actual timing quantization is approximately zero. However, jitter and drifting are possible in the measured tap times.

    Timing Measurment Test #1

    The first timing test was done by tapping to 3000 beats in an audio file where were spaced 600 milliseconds apart at a tempo of MM 100. The test computer had an Intel P4 CPU running at 3.4 GHz and using Microsoft Windows XP.

    Here is a plot of the timing errors between the actual clicks in the audio

    The long-term standard deviation is equivalent to the baseline measurement (27 ms vs. a range between 27 and 33 ms). There is no significant time offset between the clicks in the audio and recorded tap times in the audio. The offset times start out about 20 ms after the beat, and after 8 minutes, shifts just in front of the beat. Note from the next graph that the time quantization is 23.22 ms, so when compared to this value, there is no significant time delay between the audio playback time and the recording keyboard keypress time.

    Also notice in the above plot that there appear to be no timing delay errors due to computer multitasking.

    The timing granularity is exactly 23.22 milliseconds. Notice that the time quantization in the above graph where the possible duration times are separated into lines which are spaced 23.22 milliseconds apart. There is no drift or jitter in the measurements as can be seen in comparable the baseline plot. However, the baseline time quantization is about 5 times smaller.

    The mean deviation between the recorded tap time and the actual stimulus time is 35 ms as demonstrated in the following plot. The baseline mean deviation is 20 ms. The difference of 15 ms is most likely due to the difference in time quantization which is also about 15 ms larger for SV than the baseline.