They might very well be defined in the future and that shouldn't affect the parsing in any way. Specifically, ffmpeg with `av1_nvenc` seems to create `GST_AV1_SEQ_LEVEL_7_3` currently and parsing such streams would fail otherwise. Fixes https://gitlab.freedesktop.org/gstreamer/gstreamer/-/issues/4589 Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/9502>