How to record system audio in MATLAB (for example: Song playing on Youtube) without third party app…
Actually my goal is to uninstall all the apps and do everything with MATLAB (i know it's silly)
Regards,
Sugar
MATLAB: RECORD SYSTEM AUDIO IN MATLAB (NO MICROPHONES)
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It took a few minutes to get the data out of the figure, and then some experimenting. I thought about low-pass filtering your signal (I still believe that would be a good idea if you intend to repeat this experiment), but decided in the interests of time to go with simple thresholding (while I watched Manchester City and West Ham).
I include all the code, including that to acquire the data from your .fig file (even though you don’t need that part).
The code:
% Get figure and data, convert to numeric from cell:
ssf = openfig('sound_speed.fig')hf2 = get(gca, 'Children')hf3xc = get(hf2, 'XData')hf3yc = get(hf2, 'YData')hf3xd = cell2mat(hf3xc);hf3yd = cell2mat(hf3yc);trshld = -0.6; % Threshold arbitrary, estimated from plot
% Threshold first:
pulse1 = find(hf3yd(1,:) < trshld);pulse2 = find(hf3yd(2,:) < trshld);Fs = 4000; % Sampling frequency (Hz)
% Equalise vector lengths:
pl1 = length(pulse1);pl2 = length(pulse2);vlen = min(pl1, pl2);pulsx = pulse1(1:vlen); % Lengths in samples
pulsy = pulse2(1:vlen);pulsxt = pulsx/Fs; % Lengths in seconds
pulsyt = pulsy/Fs;% Subtract:
PulsDs = pulsx - pulsy; % Difference in microphones arrival times (samples)
PulsDt = pulsxt - pulsyt; % Difference in microphones arrival times (seconds)
% Take mean:
PulsDsM = mean(abs(PulsDs));PulsDtM = mean(abs(PulsDt));MicDist = 1.66; % Distance between microphones (m)
Csc = MicDist/PulsDtM % Calculated speed of sound (m/s)
fprintf(1,'\n\n\tSpeed of sound = %.3f m/s\n\n', Csc)The result:
Speed of sound = 390.588 m/sIf you intend to repeat this experiment over time, I suggest:
- Develop an appropriate low-pass filter
- Develop an adaptive threshold or other peak- or pulse-detection algorithm
- Record everything that can affect the air density and therefore the speed of sound (temperature °K, barometric pressure, relative humidity, etc.)
- Collect data over time and do regressions (and plots if the function space permits) of the various variables and how they affect the speed of sound over time
- This sounds like a cool advanced secondary or undergraduate university physics experiment!
On Windows, you need a special device driver for that, and it is incompatible with directsound . See https://www.mathworks.com/matlabcentral/answers/386734-how-do-i-get-sound-data-from-a-speaker#answer_309137
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