Re: [SoX-devel] effect to write waveforms to image file

[Ulrich K. <ul...@ch...>]

armin walland <ar...@qw...>:

> i also tried using sox's downsample effect, but that didn't seem to make much
> of a difference:

You may have fallen into a trap here (that I didn't warn you about):  
If you tried
   sox input output downsample 100
(or similar), then SoX automatically turned this into
   sox input output downsample 100 rate
to return to the original sample rate. I.e. not only do you still have  
the original number of samples to process, there's also the additional  
processing time for the rate effect. (Plus, the result is probably  
garbage.)

Instead, you need to specify the new sample rate as in
   sox input -r 480 output downsample 100
(if your input is 48000 Hz). If you don't know the sample rate  
beforehand, a workaround is to use speed with the same factor as  
downsample:
   sox input output downsample 100 speed 100
You should be aware in case you use this workaround that the length  
(measured in time units) is also cut in 100 here.

Ulrich