[SciPy-user] scipy tutorials

Gary Ruben gruben at bigpond.net.au
Fri Jun 24 21:19:26 CDT 2005

Hi Matt,
First, thanks for producing and advertising the existence of these.

I thought I'd try your Echo Cancellation tute. A few problems I found:

The comment "the python sound docs at python.org are an excellent 
resource." isn't enough info for me to easily find the docs you're 
talking about - in fact I quickly gave up. Perhaps adding a "search for 
'foo'" would help.

You need to add a line to make it stand-alone:

 >>> from scipy import *

The first time I tried this:

 >>>    original_signal[i] = struct.unpack('B',osf.readframes(1))[0]

I got a traceback

Traceback (most recent call last):
   File "<pyshell#22>", line 2, in -toplevel-
     original_signal[i] = struct.unpack('B',osf.readframes(1))[0]
error: unpack str size does not match format

so presumably there are restrictions on the .wav file format. I tried a 
different .wav file and it worked fine. Perhaps providing a short .wav 
file of the correct format would be a good idea. In fact, I found that 
the .wav I use locks up at the correlation step, presumably because it's 
too big (65k ~ 5 seconds), so at least put a comment in to keep the .wav 
of the order of a second. I'll try again later.

Half-way through you change from using original_signal to osig
This needs fixing.

You haven't shown the commands to produce the waveform plots.
Something simple like
 >>> from pylab import *
 >>> plot(csig)
[<matplotlib.lines.Line2D instance at 0x028909B8>]
 >>> show()

unless you want to assume usage with Ipython in interactive mode.

I had a quick look at the DTMF tute. Since, this contains plotting 
instructions, I assume it is intended to be done before the Echo 
Cancellation tute. This needs commenting or at a minimum reordering of 
the links on the webpage.

I haven't run through it, but I noticed there's a syntax-error 
generating typo:

 >>> From scipy import *
lower case

Hope this helps,
Gary R.

Matt Fishburn wrote:
> Hello all,
> I've written some basic scipy tutorials, located at:
> http://scipy.mit.edu/
> The tutorials are meant to be a resource to people starting to work with 
> scipy/matplotlib/ipython.  A few more tutorials should be coming over 
> the next month or so.  Please let me have any feedback - if you find the 
> tutorials useful, if you thought something wasn't explained well, etc.
> -Matt Fishburn

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