Add tee examples

README.md

@@ -11,6 +11,7 @@ A few Python examples are also included for when you need GStreamer to be dynami
 * [Mixing video & audio](mixing.md)
 * [Images](images.md)
 * [Capturing images](capturing_images.md)
+* [Sending to multiple destinations (tee)](tee.md)
 * [Sending/receiving video from shared memory](memory_transfer.md)
 * [Network transfer](network_transfer.md) (including how to send so that VLC can preview)
 
@@ -29,9 +30,10 @@ A few Python examples are also included for when you need GStreamer to be dynami
 
 ## Interacting with the GStreamer pipeline
 
-If you want to interact with GStreamer after it's started (e.g. respond to an event, or dynamically change a pipeline), the command-line GStreamer doesn't really cut it. Instead you have two options:
+If you want to interact with GStreamer after it's started (e.g. respond to an event, or dynamically change a pipeline), the command-line GStreamer doesn't really cut it. Instead, here are some options:
 
 * *[GStreamer Daemon (gstd)](https://github.com/RidgeRun/gstd-1.x)* - allows setting and updating via a TCP connection
+* *[Snowmix](http://snowmix.sourceforge.net/) - an open-source live video mixer
 * *Develop using the GStreamer library*, in either [C](https://gstreamer.freedesktop.org/documentation/application-development/basics/helloworld.html), [Python](https://github.com/GStreamer/gst-python), or [C#/.NET](https://github.com/GStreamer/gstreamer-sharp)
 
 ### Python with GStreamer

tee.md

@@ -0,0 +1,42 @@
+# Multiple outputs (tee)
+
+The `tee` command allows audio & video streams to be sent to more than one place.
+
+Here's a simple example that sends shows video test source twice (using `autovideosink`)
+
+```
+# The two windows may overlay on top of each other
+gst-launch-1.0 \
+    videotestsrc ! tee name=t \
+    t. ! queue ! videoconvert ! autovideosink \
+    t. ! queue ! videoconvert ! autovideosink
+```
+
+Here's an example that sends video to both `autovideosink` and a TCP server (`tcpserversink`).
+Note how `async=false` is required on both sinks.
+
+```
+gst-launch-1.0 videotestsrc ! \
+    decodebin ! tee name=t \
+    t. ! queue ! videoconvert ! autovideosink async=false \
+    t. ! queue ! x264enc ! mpegtsmux ! tcpserversink port=7001 host=127.0.0.1 recover-policy=keyframe sync-method=latest-keyframe async=false
+```
+
+However, as discussed [here](http://gstreamer-devel.966125.n4.nabble.com/tee-won-t-go-in-playing-state-td4680128.html), `async=false` can cause issues. Adding `tune=zerolatency` to the `x264enc` also resolves the issue.
+
+```
+gst-launch-1.0 videotestsrc ! \
+    decodebin ! tee name=t \
+    t. ! queue ! videoconvert ! autovideosink \
+    t. ! queue ! x264enc tune=zerolatency ! mpegtsmux ! tcpserversink port=7001 host=127.0.0.1 recover-policy=keyframe sync-method=latest-keyframe
+```
+
+You can also use `tee` in order to do multiple things with inputs. This example combines two audio visualisations:
+
+```
+gst-launch-1.0 filesrc location=$SRC ! decodebin ! tee name=t ! \
+    queue ! audioconvert ! wavescope style=color-lines shade-amount=0x00080402 ! alpha alpha=0.5 ! \
+    videomixer name=m background=black ! videoconvert ! vertigotv ! autovideosink \
+    t. ! queue ! audioconvert ! spacescope style=color-lines shade-amount=0x00080402 ! alpha alpha=0.5 ! m. \
+    t. ! queue ! autoaudiosink
+```