Understanding audiodynamic plug-in

[Ian Davidson]

I think that I have found a documentation bug (or two) with audiodynamic 
- but maybe something more serious.  Or, perhaps I don't understand what 
I have asked it to do.

First, the documentation in the GStreamer Good Plugins 1.0 Plugins 
Reference Manual gives a couple of example uses where the property 
'rate' is specified - but this should be 'ratio'.

Also, in the documentation, it states that threshold has allowed values 
of 0,1, but gst-inspect shows that this is a range from 0-1, not 
discrete values.

Second.
My understanding is that audiodynamic can work in one of two modes - 
compressor or expander.  I thought that in compressor mode, it would 
take the loud bits of the audio and make them quieter and that in 
expander mode, it would find the quiet bits and make them louder.  I 
used the following pipeline

gst-launch-1.0 -v filesrc location=/home/ian/Music/file1.wav ! wavparse 
! audiodynamic mode=expander characteristics=soft-knee threshold=0.5 
ratio=40 ! wavenc ! filesink location=/home/ian/Music/new2.wav

I admit that I don't know what values I might want to set for threshold 
or ratio - but the effect of this pipeline was to make the quiet bits go 
very quiet indeed.

The documentation could probably do with some explanation of threshold 
more than "Threshold until the filter is activated."  What is it the 
threshold of?  When the threshold is exceeded, what does the 'ratio' 
actually do?

By the way - what I was hoping I could do was to take a recording and 
'boost' the quiet bits a bit.  What would be sensible values to use for 
this (as a starting point)?

Ian
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