From e8b8c51238c24803edb62e634999402e7a3b70be Mon Sep 17 00:00:00 2001
From: Matthew Clark <matthew1000@gmail.com>
Date: Sun, 25 Feb 2018 17:16:08 +0000
Subject: [PATCH] Add memory transfer basics

---
 README.md          | 19 +++++++++++++++++++
 memory_transfer.md | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+)
 create mode 100644 memory_transfer.md

diff --git a/README.md b/README.md
index 2e3ff9f..3505535 100644
--- a/README.md
+++ b/README.md
@@ -9,6 +9,7 @@ This series of docs provides a cheat sheet for Gstreamer on the command-line.
 * [RTMP](rtmp.md)
 * [Mixing video](mixing.md)
 * [Capturing images](capturing_images.md)
+* [Sending/receiving video from shared memory](memory_transfer.md)
 
 ## Sources and references
 
@@ -22,3 +23,21 @@ This series of docs provides a cheat sheet for Gstreamer on the command-line.
 * http://wiki.oz9aec.net/index.php/Gstreamer_cheat_sheet
 * https://github.com/xmementoit/gstreamerCheatsheet/blob/master/README.md
 
+## Interaction
+
+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:
+
+* *[GStreamer Daemon (gstd)](https://github.com/RidgeRun/gstd-1.x)* - allows setting and updating via a TCP connection
+* *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
+
+Good GStreamer Python resources include:
+
+* [Python GStreamer Tutorial](http://brettviren.github.io/pygst-tutorial-org/pygst-tutorial.html)
+* [Function reference](http://lazka.github.io/pgi-docs/#GstApp-1.0)
+
+# Problems or suggestions with this guide?
+
+If you spot anything incorrect or incomplete, reports are welcome, either using [issues](issues) or [pull requests](pulls)
+
diff --git a/memory_transfer.md b/memory_transfer.md
new file mode 100644
index 0000000..a61d1be
--- /dev/null
+++ b/memory_transfer.md
@@ -0,0 +1,35 @@
+# Capturing images (GStreamer command-line cheat sheet)
+
+The [`shmsink`](https://gstreamer.freedesktop.org/data/doc/gstreamer/head/gst-plugins-bad/html/gst-plugins-bad-plugins-shmsink.html) element allows you to write video into shared memory, from which another gstreamer application can read it with [`shmsrc`](https://gstreamer.freedesktop.org/data/doc/gstreamer/head/gst-plugins-bad/html/gst-plugins-bad-plugins-shmsrc.html).
+
+### Puttingn a stream into memory
+
+```
+gst-launch-1.0 -v videotestsrc ! \
+    'video/x-raw, format=(string)I420,  width=(int)320, height=(int)240, framerate=(fraction)30/1' ! \
+    queue !  identity ! \
+    shmsink wait-for-connection=1 socket-path=/tmp/tmpsock  shm-size=20000000 sync=true  
+```
+
+Another example, this time from a file rather than test source, and keeping the audio local:
+
+```
+gst-launch-1.0 filesrc location=$SRC ! \
+    qtdemux name=demux  demux.audio_0 ! queue ! decodebin ! audioconvert ! audioresample ! \
+    autoaudiosink \
+    demux.video_0 ! queue ! \
+    decodebin ! videoconvert ! videoscale ! videorate ! \
+    'video/x-raw, format=(string)I420,  width=(int)320, height=(int)240, framerate=(fraction)30/1' ! \
+    queue !  identity ! \
+    shmsink wait-for-connection=0 socket-path=/tmp/tmpsock  shm-size=20000000 sync=true  
+```
+
+### Reading a stream from memory
+
+```
+gst-launch-1.0 shmsrc socket-path=/tmp/tmpsock ! \
+    'video/x-raw, format=(string)I420, width=(int)320, height=(int)240, framerate=(fraction)30/1' ! \
+    autovideosink
+````
+
+