mirror of
https://github.com/lhns/steam-frame-nix.git
synced 2026-10-06 04:04:16 +02:00
Pierre Kisters
0d9a238e5a
steamFrame.launchers.<desktop ID> takes the app's own entry (a Flatpak's
export, a Nix package's or a host file) and rewrites only its command lines
(hostEnv, env, flatpakArgs, args, wrappers) and the keys asked for
(mimeTypes, defaultFor, settings), so name, icon, translations and actions
stay the app's and follow its updates.
- Package entries are rewritten at build time; Flatpak/host file entries at
runtime by steam-frame-nix-launchers into
<session.runtimeDir>/steam-frame-nix/applications (tmpfs), on switch, at
login and when Flatpak installs/updates apps (path unit); the Home Manager
links point there.
- keyring.{enable,electron} replaces steamFrame.keyring.{flatpaks,programs}
(clean break: the old options fail with the new form).
- Firefox's launcher is the Flatpak's entry with the profile wrapper in
front (no --profile for the profile manager); Jellyfin's hardware
decoding sets flatpakArgs and env.
- cleanup --all removes the tmpfs entries.
- Check on copies of the real Element, KRDC, Firefox, gedit, Jellyfin and
Claude entries, quoting and generator behaviour.
89 lines
3.5 KiB
Markdown
89 lines
3.5 KiB
Markdown
# Jellyfin hardware decoding
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`jellyfin.hardwareDecoding.*`, module `jellyfin`, for the Flathub
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[Jellyfin Desktop](https://github.com/jellyfin/jellyfin-desktop) Flatpak
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(`org.jellyfin.JellyfinDesktop`), which plays video with libmpv. Options:
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[README, Options](../README.md#options).
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## Problem
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Video is decoded in software (1080p H.264: ~40 % CPU). The Frame's hardware
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decoder is a V4L2 memory-to-memory device (`qcom-iris`, `/dev/video*`),
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which
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- the Flatpak can't open: its `devices=dri` covers only the GPU, and Flatpak
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has nothing between that and `devices=all`;
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- mpv never tries: Jellyfin hard-sets `hwdec=auto-copy`, and mpv's `auto`
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probing leaves out V4L2 M2M on purpose (its quality varies by SoC).
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Jellyfin has no way to pass mpv options.
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## What you get
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A [launcher](launchers.md) (the Flatpak's own entry, rewritten under its
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ID, so the KDE menu and the "+" menu start it) runs the Flatpak with device
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access (`devices=all`)
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and makes mpv use `hwdec` (default `v4l2m2m-copy,auto-copy`); explicit
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values such as `no` stay. mpv tries the listed decoders in order and falls
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back to software decoding per stream. With the default, 1080p H.264 plays
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at ~15-20 % CPU. Changes take effect at the next start of Jellyfin.
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## Configuration
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Installing the Flatpak is up to you, e.g.
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`flatpak install --user flathub org.jellyfin.JellyfinDesktop`, or with
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nix-flatpak:
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```nix
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services.flatpak.packages = [ "org.jellyfin.JellyfinDesktop" ];
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steamFrame.jellyfin.hardwareDecoding.enable = true;
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```
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From a terminal, start it with the command line of
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`steamFrame.jellyfin.hardwareDecoding.command` (or the one of `grep ^Exec=
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~/.local/share/applications/org.jellyfin.JellyfinDesktop.desktop`); its
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output shows `mpv-hwdec-shim: hwdec "auto-copy" -> "v4l2m2m-copy,auto-copy"`,
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then mpv's `Using hardware decoding (v4l2m2m-copy)`.
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## Caveats
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- `devices=all` gives the app all of `/dev` (cameras, input devices, ...),
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not just the decoder.
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- V4L2 M2M decoding quality varies with drivers and codecs. Tested: 8-bit
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H.264; 10-bit HEVC is untested. mpv falls back to software only when the
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decoder fails; for streams that decode with artifacts, disable the option
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(or set `hwdec = "auto-copy"`, Jellyfin's own value).
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## How it works
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### The shim
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An `LD_PRELOAD` shim (`modules/jellyfin/mpv-hwdec-shim.c`, a few libmpv
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wrappers, only libc) rewrites an `hwdec` value starting with `auto` (set
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through libmpv's `mpv_set_*` functions) to `$SFN_MPV_HWDEC` (the `hwdec`
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option). It is preloaded from the Nix store; only its store path is exposed
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(read-only) to the sandbox. It would work for any libmpv app that sets
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`hwdec=auto*`, but only Jellyfin Desktop is set up here.
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### The launcher
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Nothing is written to Flatpak's overrides: the launcher
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`steamFrame.launchers."org.jellyfin.JellyfinDesktop"` passes device access
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and the shim as `flatpak run` options (`flatpakArgs`, `env`), so they apply
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to launches from the entry and are gone with it. Its command lines (the
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entry's and the four actions') become
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```sh
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flatpak run --branch=stable --arch=aarch64 --command=jellyfin-desktop \
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--device=all --filesystem=<shim>:ro \
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--env=LD_PRELOAD=<shim>/lib/mpv-hwdec-shim.so \
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--env=SFN_MPV_HWDEC=v4l2m2m-copy,auto-copy org.jellyfin.JellyfinDesktop
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```
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(`command` is about this line, with the store path and without the
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entry's `--branch`/`--arch`/`--command`.)
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Older versions used a Flatpak override (via nix-flatpak or a Home Manager
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link) and a shim copy in `~/.var/app/org.jellyfin.JellyfinDesktop`;
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`steam-frame-nix-cleanup` removes their entries from the override and the
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copy.
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