Recorded Audio is Shorter than Expected

I am trying to use dsp tool box to do real-time audio recording. I use tic toc to time it. However, recorded audio is always shorter than desired time. I am wondering what might cause it. Here is my coded:

close all;
clear all;
clc

frameLength = 1024;
fs=48000;
audioFrameLength=1024;

fileWriter = dsp.AudioFileWriter( ...
   'Filename', 'test_mic_array.wav', ...
    'SampleRate',fs,...
    'DataType','int32');

deviceWriter=audioDeviceWriter(...
    'SampleRate', fs,...
    'BitDepth','24-bit integer')

deviceReader = audioDeviceReader(...
 'Device', 'miniDSP ASIO Driver',...
 'Driver', 'ASIO', ...
 'SampleRate', fs, ...
 'NumChannels', 8 ,...
 'SamplesPerFrame', audioFrameLength,...
 'BitDepth', '32-bit float',...
 'OutputDataType','int32');
setup(deviceReader)

scope = timescope( ...
    'SampleRate',fs, ...
    'TimeSpan',2, ...
    'BufferLength',fs*2*2, ...
    'YLimits',[-2^32,2^32], ...
    'TimeSpanOverrunAction',"Scroll");

reverb = reverberator( ...
    'SampleRate', 48000, ...
    'PreDelay',0.5, ...
    'WetDryMix',0.4);
% fprintf('Latency due to device buffer: %f seconds.\n',deviceReader.SamplesPerFrame/deviceReader.SampleRate)

disp('Recording now.')
tic
while toc < 20
    acquiredAudio = deviceReader();
    acquiredAudio=bitshift(acquiredAudio,10);
    scope(acquiredAudio)
    deviceWriter(acquiredAudio);
    fileWriter(acquiredAudio);
end
disp('Recording complete.')

release(fileWriter)
release(deviceReader)
release(deviceWriter)
release(reverb)
release(scope)

Answer 1

[jibrahim]

Hi Xiwen,

I suspect the scope is taking a long time to set up the first time you call it.

Consider adding this code outside of the for loop to remove this overhead:

setup(scope,zeros(frameLength,1,'int32'))
scope.show