How to separate each tone from DMTF signal stream

I read an example from Matlab on how to perform the Goertzel but then I am having problem to understand how we can separate the signal which contains a number of tones plus a silent separate between tones.

My question really is: how do we determine which time interval for which tone? Assume that the duration for the tone and the separation are not fixed (otherwise, the problem becomes simple)

An example of a DTMF stream can be downloaded from

http://www.ee.columbia.edu/~dpwe/sounds/dtmf/dtmfM1.wav

[Walter Roberson]

http://www.mathworks.co.uk/matlabcentral/answers/54711-dtfm-decoding-using-goertzel-algorithm-and-peak-picking

[MatlabNewbie01232015]

Thanks