Update developer section, add Filter API tutorials

docs/Developers/index.md

@@ -1,8 +1,49 @@
+---
+title: GPAC developer guide
+---
 
-## Developer resources
+## Contributing
+
+A complex project like GPAC wouldn’t exist and persist without the support of its community. Please contribute: a nice message, supporting us in our communication, reporting issues when you see them … any gesture, even the smallest ones, counts. 
+
+## Getting support and reporting issues 
+
+Please use [github issues](https://github.com/gpac/gpac/issues) for feature requests and bug reports. When filing a request there, please tag it as feature-request.
+
+
+## API documentation
+
+The [API documentation](https://doxygen.gpac.io/modules.html) provides information on the GPAC  Filter API.
+
+GPAC's core is writen in C, but it can be easily extended using [Javascipt Filters](/Developers/javascript), used in a [Python](/Howtos/python) or [NodeJS application](/Developers/javascript).
+
+
+## Tutorials
+
+- [Intro to Filter Session](/Developers/tutorials/filter-session-intro)
+- [Writing a custom Filter](/Developers/tutorials/custom-filter)
+
+
+## Building
+
+Detailed build [Build](/Build/Build-Introduction) instructions for MP4Box and GPAC on all supported platforms.
+
+
+## Testing
+
+Learn how to [build and run GPAC's test suite](/Build/tests/GPAC_tests).
+
+The <a href="https://github.com/gpac/testsuite/tree/master/scripts" target="_blank">testsuite scripts</a> is always a good place to understand GPAC tools usage.
+
+
+## Continuous integration
+
+GPAC is continuously built and tested through a buildbot server:
+
+* Build status of GPAC: <a href="https://buildbot.gpac.io" target="_blank">buildbot.gpac.io</a>
+* Tests status of GPAC: <a href="https://tests.gpac.io" target="_blank">tests.gpac.io</a>
+
+
+## Archives
 
-* current build status of GPAC: <a href="https://buildbot.gpac.io" target="_blank">buildbot.gpac.io</a>
-* current test suite status of GPAC: <a href="https://tests.gpac.io" target="_blank">tests.gpac.io</a>
-* C API documentation: <a href="https://doxygen.gpac.io/modules.html" target="_blank"> doxygen.gpac.io</a>
-* the <a href="https://github.com/gpac/testsuite/tree/master/scripts" target="_blank">testsuite scripts</a> might give you additional info on how to use GPAC tools
 * tips and tricks in our [github discussions](https://github.com/gpac/gpac/issues?utf8=%E2%9C%93&q=) and our old [sourceforge forums](https://sourceforge.net/p/gpac/discussion/)

docs/Developers/javascript.md

@@ -0,0 +1,16 @@
+
+Javascript developers have two options to work with GPAC, the most appropriate solution depends on the project's goal:
+
+## Javascript Filters
+
+The JS filter API makes it easy to **extend gpac** using the internal QuickJS runtime, giving access to the Filter API for frame and packet processing, but also APIs foradaptative streaming, compositing, storage, ...
+
+Some of the gpac built-in filters - eg. [avgen](Filters/avgen), [avmix](Filters/avmix) - are actualy implemented as custom javascript filters. Their source code can be found under the[`share/scripts/jsf`](https://github.com/gpac/gpac/tree/master/share/scripts/jsf) directory.
+
+[JSF documentation](/Howtos/jsf/jsfilter){ .md-button }
+
+## NodeJS
+
+GPAC's NodeJS bindings allow **writing custom NodeJS applications**. It differs slightly from the Javascript Filters API available in the QuickJS runtime. 
+
+[NodeJS documentation](/Howtos/nodejs){ .md-button }

docs/Developers/tutorials/GPAC-concepts.md

@@ -0,0 +1,40 @@
+
+## What is GPAC ?
+
+The **GPAC Filter API** is at the core of the [MP4Box and GPAC](Howtos/gpac-mp4box) applications.
+
+The `gpac` application allows building media pipeplines by conveniently [combining and configuring Filters](Filters/filters_general) from the command line. 
+
+Filters are configurable processing units consuming and producing data packets. 
+
+GPAC provides a wide range of Filters supporting advanced media protocols, formats, codecs, for input, output and processing tasks. 
+
+It defines the infrastructure and helper classes to develop applications with advanced media capabilities.
+
+
+### Concepts
+
+**Filter Session**
+
+- [API documentation](https://doxygen.gpac.io/group__fs__grp.html#details)
+- [tutorial](https://git.gpac-licensing.com/slarbi/API_FIlters_tutos/src/branch/master/T0_Filters_session/simple%20gpac%20session.md)
+
+**Filter**
+- [API documentation](https://doxygen.gpac.io/group__fs__filter.html#details)
+
+**Filter Properties**
+- [API documentation](https://doxygen.gpac.io/group__fs__props.html#details)
+- [Built in Properties](https://wiki.gpac.io/Filters/filters_properties/?h=properties)
+
+**Filter Events**
+- [API documentation](https://doxygen.gpac.io/group__fs__evt.html#details)
+
+**Filter PIDs & Capabilities**
+- [API documentation](https://doxygen.gpac.io/group__fs__pid.html)
+
+**Filter Packet**
+- [API documentation](https://doxygen.gpac.io/group__fs__pck.html#details)
+
+**Custom Filter**
+- [doxygen](https://doxygen.gpac.io/group__filters____cust__grp.html#details)
+- [writing a custom Filter]()