I'm going to assume that you mean the Signal Processing Blockset, since the DSP System Toolbox did not exist in R2010a.
In R2010a with SP blockset, you can use the System object signalblks.MultimediaFileReader.
For example:
filename = 'youravifile.avi';
hmfr = signalblks.MultimediaFileReader(filename,...
'AudioOutputPort',true,'VideoOutputPort',false);
while ~isDone(hfmr)
audio = step(hfmr);
end
Every time step is called audio contains one frame of the audio. In the above, the next frame is overwriting the previous one, but you can save the audio frames or directly write them to a file with signalblks.MultiMediaFileWriter
