How to reduce Audio Latency by DSP System Toolbox ?

I have been working on my ANC project. For this I have two microphone inputs and one loud speaker output, but initially I am using single microphone and dspStreamingPassthrough to pass microphone input to loud speaker. Here is my code

% Initialization
numIterations = 500;
 % Construct sources (for all inputs)
src1 = dsp.AudioRecorder('DeviceName','Mikrofon (USB-Audiogerät)','NumChannels',1);
% Construct sinks (for all outputs)
sink1_1 = dsp.SpectrumAnalyzer('SampleRate',44100, ...
    'PlotAsTwoSidedSpectrum',false, ...
    'ShowLegend',true);
sink1_2 = dsp.TimeScope('BufferLength',44100, ...
    'SampleRate',44100, ...
    'TimeSpan',1, ...
    'ShowLegend',true, ...
    'ShowGrid',true, ...
    'YLimits',[-0.5 0.5]);
sink1_3 = dsp.AudioPlayer('BufferSizeSource','Property','BufferSize',1024,...
'QueueDuration',0,'OutputNumUnderrunSamples',true);
sink1_3.DeviceName = 'Lautsprecher (USB-Audiogerät)';
% Stream processing loop
clear dspStreamingPassthrough;
for i = 1:numIterations
    % Sources
    in1 = step(src1);

      % User Algorithm
      out1 = dspStreamingPassthrough(in1);

      % Sinks
      step(sink1_3,out1);
      step(sink1_1,out1);
      step(sink1_2,out1);
      nUnderrun=step(sink1_3,out1);
  end
  % Clean up
  release(src1);
  release(sink1_1);
  release(sink1_2);

I am using Windows DirectSound Audio driver ( I cannot use ASIO driver as I cannot access individual audio devices names. ! )

Now I have the audio latency of 1.2 seconds i.e if I say ''hello'' in microphone now, after 1.2 seconds speaker is saying ''hello''(this is absolutely with out any audio input data processing just 'dspStreamingPassthrough').

How to reduce this incredible delay ?

For my project of 1 meter length pipe(air duct), I should be able to process the data in 1.7 msec or less !!

I have tried with lowest 'BufferSize' and lowest 'QueueDuration' possible !!

What other parameters can influence to speed up this process? Is it possible with MATLAB or not ?

PS:

• sorry for whole code.
• I am using a cheap quality Sound card (7 euros)

Answer 1

[Walter Roberson]

You will not be able to reach 1.7 msec.

Using ASIO, Mathworks says they can get 2.7 msec; see http://www.mathworks.com/matlabcentral/answers/23675-how-to-produce-a-continuous-sound

See also http://www.mathworks.com/matlabcentral/answers/102950-how-do-i-use-asio-alsa-and-other-apis-to-communicate-with-pc-audio-hardware-from-simulink

I do not know what the practical limits are for DirectSound. I also do not know anything about selecting individual devices with ASIO.