[pulseaudio-discuss] [RFC 2/2] pulseaudio modules - adding documentation for two more modules

[Nandor Han]

Adding the missing documentation for `module-filter-heuristics` and
`module-filter-apply`.

Most of the documentation was made based on the Victor Gaydov's article
(https://gavv.github.io/blog/pulseaudio-under-the-hood/#autoloading-filters)

This also fixes the PulseAudio bug 96804
(https://bugs.freedesktop.org/show_bug.cgi?id=96804)

Signed-off-by: Nandor Han <nandor.han at ge.com>
---
 .../PulseAudio/Documentation/User/Modules.mdwn     | 33 ++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/Software/PulseAudio/Documentation/User/Modules.mdwn b/Software/PulseAudio/Documentation/User/Modules.mdwn
index 75d5706..354b011 100644
--- a/Software/PulseAudio/Documentation/User/Modules.mdwn
+++ b/Software/PulseAudio/Documentation/User/Modules.mdwn
@@ -948,6 +948,39 @@ This is a compatibility module for libesd based autospawning of PulseAudio. Don'
 This is a compatibility module for libesd based autospawning of PulseAudio. Don't use it directly.
 
 
+### module-filter-apply
+
+Tracks when a stream is created, moved and properties list changed.
+
+Checks if this is a group filter, which uses a paired source and sink and therefore requires a paired source output and sink input.
+In this case, the filter is loaded only if the paired stream exists as well.
+
+Two streams are considered paired if they have the same "filter.apply" property and the same stream group identifier.
+Currently, the only group filter is "echo-cancel".
+
+Checks if the user did specify additional module paraterer via the "filter.apply.<filter_name>.parameters" property.
+
+Loads the "module-<filter_name>" module. The "master" or the "source_master" and ""sink_master"" arguments are set to the name of the source or sink to which the stream or paired streams are currently connected.
+If the user did specify additional parameters, they are also passed to the module.
+
+Finds the newly loaded filter source or sink.
+
+Moves the stream or paired streams to the filter source or sink.
+
+Parameters:
+
+* autoclean
+    * Unload unused filters every ten seconds if true.
+
+### module-filter-heuristics
+
+Tracks when a stream is created or moved.
+
+Converts the "filter.want" to "filter.apply" property, unless is filtered out.
+
+The filtering list is hard-coded, and currently there is only one situation where "echo-cancel" is filtered out for "phone" indendded role.
+
+
 ### module-loopback
 
 **Since 0.9.16.** This allows one to route audio from a source directly back to a sink.
-- 
2.10.1