Realise a plugin

I would like to make an Audacity plugin but I did not find manual or web site for the first steps.

Does exist any documentation to help me or some examples ?

Thanks

I’m working with Visual C++ (2008) on Windows
I build Audacity last version on SVN

Audacity supports a number of different plug-in formats, including VST (mostly on Windows), LADSPA, AU (Mac OS X only) and Nyquist.
Of these, probably the easiest to write are “Nyquist” plug-ins.

Because Nyquist plug-ins are specifically for Audacity, we have quite a lot of information. See this post: https://forum.audacityteam.org/t/manuals-and-reference-material/32817/1

I try to use Nyquist plugin but I think it will be not OK for import plugin ?

What do you mean by “import plugin”?
What are you wanting to do?

I have some data in file with a specific format and I would like to import in Audacity to analyse , modify …
So I need plugin to import and then plugin to use data

What is the format?
Is the format supported by FFmpeg?

This is not a standard format so I need to create a plugin to import what I need

Are you an accomplished C/C++ programmer?

You’re not giving me much information to go on, but assuming that it audio format, probably the easiest way would be to add support for your non-standard format to FFmpeg, then build Audacity against your custom FFmpeg headers.

Alternatively you could try writing a “module” type plug-in. Unfortunately there is not much documentation about this, but there are a couple of example modules included in the Audacity source code. There is some information in the Audacity wiki (it may be a bit out of date as the API is still undergoing development):
http://wiki.audacityteam.org/wiki/Experimental_Modules
http://wiki.audacityteam.org/wiki/GUI_Plugins

Also see here for information relevant to developers: http://wiki.audacityteam.org/wiki/Category:For_Developers

Thanks for your help.
Sorry about the description of my needs but it’s a new professional project (so C++ programming is OK for me) and I have not a lot of informations so I try ta have informations about all sorts of plug in.
I will try to see all possibilities with Nyquist to begin

I compiled the “mod-null” module → I get the DLL file but Audacity doesn’t load it … Where should be the file “mod-null.dll” : in Audacity.exe directory or in a subfolder ?

The others exemples need Visual 2012 so I can’t use them.

Mod-nyq-bench and mod-script-pipe compile OK with GCC.
On Linux I usually put modules in ~/.audacity-files/modules
Modules need to enabled in “Edit > Preferences > Modules” and they need to be built on the same day as Audacity is compiled.

On Windows the modules must be in a “modules” folder inside the directory where Audacity is.

Gale