[CLAM] Questions about SMSTools (Frame Segmentation).

[Matthias Geier]

Dear list.

I'm using SMSTools to process a sound file and generate an SDIF file.
Then I'm using the SDIF file and the original sound file in MATLAB.

My problem is:
When I split the original audio-file into frames with the same
settings as in SMSTools and get in some cases a different number of
frames!

Right now I'm using the standard values of SMSTools (FrameLength 2049,
HopSize 256).

Now I have some questions whose answers will hopefully help me to find
out what's the problem:

1. Does the time tag of a frame mark the beginning or the middle (or
even something else) of the frame?

2. What does the first frame include? The samples 0 to FrameLength-1?
Or first some zeros and then the samples 0 to (FrameLength-1)/2? Or
maybe first some zeros and then the samples 0 to HopSize? Or something
else?

3. How are the time-tags calculated? When I multiply the time-tags by
the sample rate, I get more or less what I expect (integer multiples
of the HopSize), but the values have a little error. This error could
be just a round-off error, but I don't know. The strange thing is,
that with bigger frame number this error increases. At about frame
number 100 it had a value of about 10^-3.

BTW, I'm using SMSTools 2 v0.1.2 on Mac OSX, because with the new
QtSMSTools I cannot yet save SDIF files (I can analyze sounds,
though).

TIA for your answer(s)/suggestion(s)
Matthias