When I first read the documentation of gst_adapter_available() and gst_adapter_available_fast() I got quite confused as it seemed that both performed the same purpose but one was slower than the other. I shared it with other people and found they also arrived at the same wrong conclusion. Hopefully this patch will make the actual purpose clearer. Fixes https://gitlab.freedesktop.org/gstreamer/gst-docs/-/issues/12 Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/7859>