How to freeze the video from a video stream in GSTREAMER?

To freeze the video from a video stream in GStreamer, you can use the "tee" element to split the video stream into two branches. One branch continues to display the video normally, while the other branch is passed through a "queue" element to buffer frames. When you want to freeze the video, you can use the "valve" element to stop the flow of frames from the first branch, and then use the "valve" element on the second branch to allow a single frozen frame to be displayed.

Here is an example pipeline:

gst-launch-1.0 videotestsrc ! tee name=t \
t. ! queue ! valve name=v1 ! videoconvert ! autovideosink \
t. ! valve name=v2 ! videoconvert ! autovideosink

In this pipeline, the "videotestsrc" element generates a test video stream. The "tee" element splits the stream into two branches, named "t". The first branch continues to display the video normally, while the second branch is passed through a "queue" element to buffer frames.

The "valve" elements are used to control the flow of the streams. The "v1" valve allows the first branch to flow normally. The "v2" valve is initially closed, which prevents the frozen frame from being displayed.

To freeze the video, you can send a message to the "v1" valve to close it, which stops the flow of frames from the first branch. Then, you can send a message to the "v2" valve to open it, which allows a single frozen frame to be displayed.

Here is an example command to freeze the video:

gst-launch-1.0 -e --gst-debug-level=3 \
videotestsrc ! tee name=t \
t. ! queue ! valve name=v1 ! videoconvert ! autovideosink \
t. ! valve name=v2 ! videoconvert ! autovideosink \
&& sleep 5 \
&& gst-launch-1.0 -e --gst-debug-level=3 \
valve name=v1 drop=true ! fakesink \
&& gst-launch-1.0 -e --gst-debug-level=3 \
valve name=v2 drop=false ! fakesink

This command runs the pipeline and displays the video normally. After 5 seconds, it sends a message to the "v1" valve to close it, which stops the flow of frames from the first branch. Then, it sends a message to the "v2" valve to open it, which allows a single frozen frame to be displayed. Finally, it sends messages to both valves to drop all remaining frames and stop the pipeline.