mpv does not close file descriptors over time

Important Information

• mpv version: mpv 0.33.1
• Linux Distribution and Version: Alpine Linux 3.14
• Source of the mpv binary: Alpine Linux packages
• Window Manager and version: none
• GPU driver and version: in-kernel i915 1.6.0

Reproduction steps

1. mpv --idle --terminal=no --input-ipc-server=/tmp/mpv20210609-3556-4mh4ad.sock --no-config --log-file=/var/video/mpv.log --vo=gpu --gpu-context=drm --hwdec=vaapi --fs=yes --profile=low-latency --no-audio --no-cache --no-osc --no-input-default-bindings --load-osd-console=no --load-scripts=no --load-stats-overlay=no
2. send multiple loadfile rtsp://... and stop commands via ipc socket

Expected behavior

mpv should close file and socket descriptors when it's done playing streams

Actual behavior

$ ls /proc/3617/fd | wc -l
26218

○ ls -lt /proc/3617/fd | head
total 0      
l-wx------    1 root     root          64 Jun 16 02:23 26194 -> pipe:[358170]
lr-x------    1 root     root          64 Jun 16 02:23 26203 -> /dmabuf:
lr-x------    1 root     root          64 Jun 16 02:23 26204 -> /dmabuf:
lr-x------    1 root     root          64 Jun 16 02:23 26205 -> /dmabuf:
lr-x------    1 root     root          64 Jun 16 02:23 26206 -> /dmabuf:
lr-x------    1 root     root          64 Jun 16 02:23 26207 -> /dmabuf:
lr-x------    1 root     root          64 Jun 16 02:23 26208 -> /dmabuf:
lr-x------    1 root     root          64 Jun 16 02:23 26211 -> /dmabuf:
lr-x------    1 root     root          64 Jun 16 02:23 26212 -> /dmabuf:

Log file

just a few loadfiles at the start: https://pastebin.com/29MPEE97

Start by reproducing the provided mpv command and sending repeated loadfile and stop commands through the IPC socket while monitoring /proc//fd. Done means file, socket, pipe, and dmabuf descriptors no longer accumulate after streams stop; the issue names no source files or tests to inspect.