Recommendations regarding command-line usage

[harmonion]

Hello,
I've just downloaded CDP version 8 for Windows.
My intention is to code all my audio manipulation exclusively by writing batch files in an ordinary word processor.
I've already read the tutorial webpage entitled "Running the CDP system" and I have no problem understanding what it says.
My question is:
Which part of the documentation would you recommend to read next, if I'm not interested in things like Soundloom or Soundshaper? There are tons of entries in the full command reference and I would rather welcome something like one large piece of text where just some of the syntax would be explained, rather than reading about all the commands/features and having a hard time deciding which ones I would try just for my introductory experiments and which ones I would learn to use later.
Thank you in advance.

[simonk]

Hi Harmonion,
Welcome to the CDP world.

If you look at the CDP homepage you will see 'Learn' in one of the dropdown menus
https://composersdesktop.com/index.html

You might try the Workshops:
https://composersdesktop.com/workshops.html#LM

or this page, which has lots of links :
https://www.composersdesktop.com/docs/html/tutorials.htm

We'd love to hear how you get on.
Have fun!
Simon

[simonk]

There's also this thread

https://unstablesound.net/cdpforum/index.php?topic=278.0

[harmonion]

Getting to know CDP, part 2:
I'm currently reading some of the entries in the full command reference documentation. In "cpvocman.htm" (i.e. the entry entitled "CDP PVOC Functions"), the description of several commands begins with statements like the following:
"The flags mentioned refer to Old Usage pre-Release 4. The documentation often refers to the -N flag (points) and the -W flag (overlap)."
Or:
"The flags mentioned (-W, -C) refer to Old Usage pre-Release 4."
Later, there's a heading which says:
"The Phase Vocoder flags â€" with CDP parameter names (since Release 4) in parentheses"
Honestly, I'm confused. Does that mean that it describes the usage of these commands for releases older than 4? If so, where am I supposed to find the description of their usage in newer versions?

Next, it keeps talking about pairs of frequencies and amplitudes. Do they really mean frequencies? Are they sure they didn't mean to say "phase shifts and amplitudes"? Aren't the specific frequencies implied from the chosen sample rate and FFT size? I've read the entire webpage from top to bottom and it still seems to me that it should actually be "phase shifts and amplitudes".

[ArcherCDP]

Hello,  Thank you for your query about PVOC usage.  The references to pre-Release 4 usage flags were put there at the time of Release 4.5 in order to alert existing users at the time to the changes.  These references are now completely redundant and the current usage and descriptions are the ones to be followed.  I will recommend that the yes, confusing, references to pre-Release 4 usage be removed from the Manual.  I myself just use the default settings, so the command lines are very simple, e.g., pvoc anal 1 infile.wav outfile.ana and pvoc synth infile.ana outfile.wav.

As to the query about frequencies and amplitudes v. phase shifts and amplitudes, I will have to check with the experts on this before replying.  To be continued.

[ArcherCDP]

CDP Software Maintenance engineer Richard Dobson writes regarding the question about PVOC frequency & amplitude v. phase shift & amplitude:

The short answer is, yes, we really do mean frequencies. Techncially, "frequency" (as a nominally continuous artefact) is defined as the rate of change of phase. This is why sometimes the phase vocoder has been referred to as a "tracking" vocoder, simnply because it tracks the (rate of) change of phase over time. A zero rate of change would equate to a constant DC level.

In the original pvoc, understood very much as an accumulating (sliding/overlapping frames) FFT-based process, data could be output in all the possible formats: raw "complex" values as delivered by the FFT, or either of amplitude/phase or all the way to ampltude/frequency. For pure analysis tasks, amp/phase is still often used. But in CDP (and likewise in Csound etc), we want to make weird transformations of the source and resynthesise it - this is very much easier and more "intuitive" with the classic amp/frequency format. It means, for example, that resynthesis can be done (from the same data) either by pvoc or by direct oscillator bank.

Some transformations (such as zeroing the amplitudes in some analysis bins) are "incorrect" mathematically (in terms of strict band-limited "linear" DSP), but composers rarely care about that. So long as the results are both interesting and mostly correlate with the intention, we just get on with it!

The "pvocex" program now included in the CDP system is a straight port of the origial pvoc (but creating pvx files), with (almost) all the original flag options.

Cheers,
Richard