Update cheatsheets

tldr/gst-transcoder-1.0

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+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# gst-transcoder-1.0
+
+> Convert media between two filetypes.
+> More information: <https://wiki.st.com/stm32mpu/wiki/Gst-transcoder>.
+
+- List available transcoding targets:
+
+`gst-transcoder-1.0 {{[-l|--list-targets]}}`
+
+- Convert from one media type to another:
+
+`gst-transcoder-1.0 {{path/to/input_file.webm}} {{path/to/output_file.mp4}}`

tldr/linux/gst-launch-1.0-v4l2src

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+---
+syntax: markdown
+tags: [tldr, linux]
+source: https://github.com/tldr-pages/tldr.git
+---
+# gst-launch-1.0 v4l2src
+
+> Read frames from a Video4Linux2 device.
+> More information: <https://gstreamer.freedesktop.org/documentation/video4linux2/v4l2src.html>.
+
+- View video in a window:
+
+`gst-launch-1.0 v4l2src device={{/dev/video0}} ! autovideosink`
+
+- Create a PipeWire node out of a v4l2 device:
+
+`gst-launch-1.0 v4l2src device={{/dev/video0}} ! videoconvert ! pipewiresink mode=provide stream-properties="properties,media.class=Video/Source" client-name="{{Virtual Camera}}"`