doc (cli/call): Update doc with new features:

Add doc for:

- `no_ui` output
- stdin/stdout redirection
- custom GStreamer pipelines

doc/libervia-cli/call.rst

@@ -100,6 +100,8 @@ v6 or higher. Here's how to navigate and use the GUI:
    You need to have installed the ``PyQt6`` package to make it work. It is the case if you
    have used `[GUI]` or `[all]` dependencies during Libervia installation.
 
+.. _no_ui:
+
 Call Interface
 ^^^^^^^^^^^^^^
 
@@ -128,17 +130,62 @@ share. It can be your entire screen or a specific application window. On X11, a
 dialog will appear, while for Wayland, a dialog provided by your environment will ask you
 to select what you want to share.
 
-example
--------
+no_ui
+-----
+
+Sometimes you don't want Libervia to create a user interface. This can be because you want
+to pipe the stream to other software or use a custom GStreamer pipeline.
+
+With ``no_ui`` output, no user interface will be created. If you don't specify audio or
+video pipeline options (see below), automatic sinks will be used, except when stdout is
+redirected (e.g., via a pipe), in which case playback is not shown at all.
+
+The following output options can be used:
+
+- **audio=AUDIO_PIPELINE**: Set a GStreamer pipeline description for audio.
+- **video=VIDEO_PIPELINE**: Set a GStreamer pipeline description for video.
+
+Custom Pipelines
+^^^^^^^^^^^^^^^^
+
+Custom GStreamer pipelines can be used as sources for outgoing streams using ``-V, --video
+VIDEO`` and/or ``-A, --audio AUDIO``. You can use GStreamer pipeline descriptions (the
+same as with the ``gst-launch`` command).
+
+For sinks (to handle incoming streams), use the ``no_ui`` output with the ``audio`` and
+``video`` options as explained in :ref:`no_ui`.
+
+Stdin/Stdout redirection
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+You can redirect stdin and/or stdout (e.g., using pipes or file redirection).
+
+For stdin, the stream format will be autodetected, and if it can be read, it will be sent
+to your peer.
+
+For stdout, the incoming stream will be copied there in WebM format. This can be used with
+file redirection to record a call.
+
+.. note::
+
+   If you record a call, be sure you have the consent of your peer.
+
+examples
+--------
 
 Pierre wants to call Louise with a GUI::
 
   $ li call make louise@example.org -O gui
 
-Louise is expecting Pierre call, and will use TUI with the ``block`` renderer to show it::
+Louise is expecting Pierre’s call and will use TUI with the ``block`` renderer to display
+it::
 
   $ li call receive -a pierre@example.net -O tui --oo renderer=block
 
+Louise wants to show a movie trailer to Pierre::
+
+  $ li call make pierre@example.net < ~/blender/Agent\ 327\ -\ Operation\ Barbershop.webm
+
 make
 ====