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README.md

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+# GStreamer Microsecond Timestamp Overlay
+
+This is an adaptation of the `clockoverlay` and `timeoverlay` plugins from gstreamer-base. Stripped bare and just overlaying the Linux epoch time, with a microsecond resolution.
+
+## Use-case Examples
+
+A single stream solution can be tested like this:
+
+```bash
+gst-launch-1.0 \
+    videotestsrc is-live=true do-timestamp=true \
+    ! msoverlay halignment=left valignment=top \
+    ! video/x-raw,format=RGB,framerate=30/1,width=640,height=480 \
+    ! videoconvert \
+    ! video/x-raw,format=NV12 \
+    ! nvautogpuh264enc tune=3 \
+    ! rtph264pay config-interval=0 pt=96 \
+    ! rtph264depay \
+    ! h264parse \
+    ! nvh264dec \
+    ! msoverlay halignment=left valignment=bottom \
+    ! autovideosink
+```
+
+Take a screenshot of the output above and subtract the top-left number from the bottom-left to see the total pipeline latency.
+
+For a more comprehensive solution we can also make the stream traverse the network stack:
+
+Server:
+
+```bash
+gst-launch-1.0 videotestsrc is-live=true do-timestamp=true ! msoverlay halignment=left valignment=top ! video/x-raw,format=RGB,framerate=60/1,width=1920,height=1080 ! videoconvert ! video/x-raw,format=NV12 ! nvautogpuh264enc tune=3 ! rtph264pay config-interval=1 pt=96 ! rtpsink uri=rtp://127.0.0.1:5000
+```
+
+Live client:
+
+```bash
+gst-launch-1.0 rtpsrc uri=rtp://127.0.0.1:5000?encoding-name=H264 ! rtph264depay ! h264parse ! nvh264dec ! msoverlay halignment=left valignment=bottom ! autovideosink
+```
+
+PNG sampling client outputting 5 frames, one per second:
+
+```bash
+gst-launch-1.0 rtpsrc uri=rtp://127.0.0.1:5000?encoding-name=H264 ! rtph264depay ! h264parse ! nvh264dec ! msoverlay halignment=left valignment=bottom ! videorate drop-only=true ! video/x-raw,framerate=1/1 ! pngenc ! multifilesink num-buffers=10 location="latency_%02d.png"
+```
+
+It is essential both the client and server run on the same machine, unless you _really_ trust your system clock accuracy.
+
+## Dependencies
+
+TODO. Basically the same dependencies as for building the gstreamer-plugins-base packages.
+
+## Building
+
+```bash
+# Assuming you're in the project root
+
+# Option A is to use the submodule to fetch the GStreamer sources:
+git submodule update --init --recursive
+
+# Older versions require deleting the builddir and omitting the '--reconfigure' option
+meson setup --reconfigure builddir
+# Option B is to use an existing GStreamer source by specifying the 'gst_root' (the GStreamer mono-repo root)
+# meson setup --reconfigure builddir -Dgst_root=${WHERE_I_CLONED_GSTREAMER}/gstreamer
+
+meson compile -C builddir
+
+# This will install the built plugin file
+meson install -C builddir
+
+# Confirm installation
+gst-inspect-1.0 | grep msoverlay
+```
+
+## Verification
+
+This should show you a fairly extensive list of options and details:
+
+```bash
+gst-inspect-1.0 msoverlay
+```