enricobuehler
9e598f8595
Two Steam Deck findings from a field report of "the decoder was not found, it fell back to H.264 — but sometimes HEVC worked". **The 4:4:4 advertisement was a promise nothing checked.** `VIDEO_CAP_444` rode the "Full chroma" setting alone. That was safe while a software HEVC decoder existed underneath it; M8 removed one (there is no permissively licensed HEVC CPU decoder, so `software_decodable_codecs()` is H.264|AV1). The host grants 4:4:4 on HEVC ONLY, and answers the resolved chroma in the Welcome before the client builds a decoder — so on a device with no 4:4:4 decode the toggle did not cost crispness, it cost the entire codec: the Vulkan rung refuses the shape at construction, VAAPI refuses it too, there is no CPU rung, and the session reconnects on H.264. AMD has no HEVC 4:4:4 decode on any silicon, so every Deck with that switch on lost HEVC. It is per-profile and default-off, which is exactly why it looked intermittent — a "Work" profile lost HEVC where "Game" kept it, same box, same host. Gated on `hevc_444_hardware_decodable`, which asks the driver through the SAME code the rung uses at construction (`VkH265Decoder::probe_stream_support`), so the advertisement and the rung that must honour it cannot disagree. Both depths are required, not either: with HDR on the host may resolve 4:4:4 10-bit, and a device offering YUV444_8 but not YUV444_10 would land in the same hole. Answering from the Vulkan rung alone is exact rather than approximate — it is the only rung in this build that implements 4:4:4 at all (`pf_vaadec::profile_for` errors on chroma_format_idc 3, pf-dxvadec refuses anything but 4:2:0, the CPU rung is 8-bit 4:2:0). Deliberately NOT extended to VIDEO_CAP_10BIT/HDR: all three rungs implement 10-bit 4:2:0, so a Vulkan-only probe there would withdraw HDR from boxes whose VAAPI/DXVA rung decodes it perfectly — a real regression against a case never observed. The bit arithmetic moves into `video::video_caps_for` so the part that was wrong is testable without a GPU, a host or a Hello; the test is verified non-vacuous against the planted original defect. **`--probe-decode` described a different device from the one that streams.** The RADV video-decode opt-in sat AFTER the --list-adapters/--probe-decode/--list-audio /--pair early exits, so the triage tool never had it. Measured on a Deck (canary e22af40f), same binary back to back: bare `--probe-decode` printed "vulkan video decode: no", "driver decode ops: none (0x0)", "no queue family advertises VIDEO_DECODE"; with RADV_PERFTEST=video_decode in the environment, "YES" and "H.264, H.265, AV1, VP9". Any Deck triage that consulted it reached the opposite of the truth. Hoisted to the top of `run`, ahead of every early exit — nothing touches Vulkan before it (`main` calls `run` directly). Gates, in the Linux container: fmt, plain `cargo build` (not only --all-targets), `clippy --all-targets -D warnings`, and 185 tests.
punktfunk-session
The Vulkan session binary: one stream per invocation in an SDL3 window — no UI toolkit,
no widgets, terminal stats. The power-user / gamescope stream client, and the stage-2
presenter of the Linux client re-architecture (punktfunk-planning:
linux-client-rearchitecture.md).
This binary is deliberately dumb: a renderer the front-ends call INTO — the GTK shell
(punktfunk-client), the WinUI shell, and the punktfunk CLI all spawn it through the
same brain (pf_client_core::orchestrate), which resolves policy (profiles, settings,
wake) and hands the result down, normally as a --resolved-spec file. It reads the
shared stores only as the compat fallback for a bare hand-launched invocation.
punktfunk-session --connect host[:port] [--fp HEX] [--launch id] [--fullscreen] [--stats]
punktfunk-session --browse host[:port] [--mgmt PORT] [--fullscreen]
--browse opens the console game library (the Skia coverflow over the animated aurora)
instead of connecting: A launches the focused title as a stream in the same window,
session end returns to the library, B quits (Gaming Mode returns). Paired hosts only —
pairing is the desktop client / Decky plugin's job. PUNKTFUNK_FAKE_LIBRARY=<file.json>
feeds canned entries with no host (portrait paths starting with / load from disk).
Reads the same identity / known-hosts / settings stores as the desktop client
(punktfunk-client), so enrolling on either side makes the other work; this binary never
connects to a host it has no pinned fingerprint for (--fp HEX overrides the store).
Pairing is punktfunk pair <host> — the CLI, which ships alongside this binary in every
package and needs no window and no toolkit either. punktfunk-session --pair still works
for one release (someone's provisioning script calls it today) but prints a deprecation
notice: pairing is a trust ceremony and belongs to the brain, not a renderer.
Stdout is the machine interface: {"ready":true} after the first presented frame,
stats: … once per second while the overlay tier isn't Off (always the full detailed
text, whatever the OSD shows; --stats forces the overlay on), one
{"error"|"ended": …} JSON line on the way out. Logs go to stderr. Exit codes: 0
clean end, 2 connect failed, 3 trust rejected / pairing required, 4 presenter
init failed.
In-stream keys match the desktop client: click captures input (Ctrl+Alt+Shift+Q releases), Ctrl+Alt+Shift+D disconnects, F11 toggles fullscreen; the controller escape chord (L1+R1+Start+Select, hold to disconnect) works the same.
The default build carries the Skia console UI (ui feature): the stats OSD and capture
hint render in-window. Ctrl+Alt+Shift+S cycles the OSD tier live — Off → Compact (one
line: fps · latency · Mb/s) → Normal (mode + end-to-end percentiles) → Detailed (decoder
path + per-stage latency equation); any tier but Off also emits the stdout mirror.
--no-default-features is the ~5 MB power-user build — same streaming, stats on stdout
only, no Skia anywhere in the dependency tree.
Decode follows the Settings preference (auto is vendor-ordered: Vulkan Video → VAAPI →
software on Linux, Vulkan Video → D3D11VA → software on Windows, with VAAPI/D3D11VA first
on Intel — every rung native since M10; see "Decode rungs" below): the Vulkan decoder runs
on the presenter's own device where the stack supports it (every vendor, zero copy); VAAPI
dmabufs import per-plane elsewhere (D3D11VA textures on Windows); software is the universal
fallback. 10-bit Main10 and HDR10 are advertised (VIDEO_CAP_10BIT|HDR): P010 decodes
through the Vulkan and VAAPI/D3D11VA paths (the CPU rung is 8-bit by contract and refuses
10-bit rather than mis-scaling it), and PQ streams present
on an HDR10/ST.2084 swapchain when the desktop offers one (KDE HDR, gamescope) or
tone-map in-shader to SDR when it doesn't (PUNKTFUNK_TONEMAP_PEAK tunes the rolloff,
default ≈1000 nits). The host still gates the upgrade behind its PUNKTFUNK_10BIT
policy.
Decode rungs (M10: native only)
This binary contains no FFmpeg. auto walks native rungs — pf-vkdecode over Vulkan
Video, then the platform's own (pf-dxvadec on Windows, pf-vaadec on Linux), then the CPU
rung (openh264/rav1d). The libavcodec rungs that used to sit under each of them are
deleted, along with pf-ffvk and the ffmpeg-next dependency.
One of the native rungs has never decoded a frame on real hardware (native VAAPI's H.264 and H.265 legs; its AV1 leg has decoded but has never been parity-checked). It runs anyway — with the libavcodec twins gone, the only thing below them is the CPU, so barring them would cost the session hardware decode outright rather than move it one rung down. What replaces the safety net is the log: every session names the rung it landed on with its evidence state,
decode rung active rung=native-vulkan codec=HEVC hardware_verified=true evidence=...
…and that line is a WARNING when nothing has ever decoded a frame through the
rung/codec pair the session chose. pf-client-core's video.rs module docs carry the full
table; read any field report about M10 against it.
Debug/bisect knobs: PUNKTFUNK_DECODER=native-vulkan|native-vaapi|native-d3d11va|software
(a pin skips the vendor order, which is how a lab run reaches a rung auto will not pick
on this device; a pinned rung that cannot open still falls through to the standard ladder,
loudly; native-vaapi also takes PUNKTFUNK_VAAPI_DEVICE=/dev/dri/renderDNNN to choose
the GPU). The pre-M10 spellings vulkan/vaapi/d3d11va named the libavcodec rungs
specifically; they are MIGRATED onto the native rung for the same hardware family, with a
warn line saying so — every desktop Settings UI offered those values, so refusing them
would end a session over a dropdown someone picked long ago.
PUNKTFUNK_PRESENT_MODE= mailbox|fifo|immediate|fifo_relaxed (default MAILBOX, FIFO where the surface offers no
MAILBOX — AMD on Windows), PUNKTFUNK_VK_DEVICE=<index> (multi-GPU), and
PUNKTFUNK_HW_FAULT=import (fault every VAAPI dmabuf import — proves the three-strike
demotion to software on healthy hardware).
PUNKTFUNK_AU_FAULT=drop|truncate|flip[:period] deliberately corrupts decoder input on the
native Vulkan lane (default period 60 — one AU a second at 60 fps; inert everywhere else, and
inert entirely if the value doesn't parse). drop swallows the AU, so the next one references a
picture that was never decoded — the bitstream planner catches it immediately. truncate delivers
a picture whose slice data stops mid-frame and flip alters one byte deep in the payload: both
parse perfectly, so only the driver's per-frame decode-status query can see them, and neither is
visible at all on a driver without queryResultStatusSupport. Watch the
result on the Detailed stats line's integrity: term (damaged = concealment the planner caught,
refused = AUs the decoder rejected outright, driver-failed = the hardware's own verdict, run
= consecutive frames with no picture, worst run = the longest such stretch of the session — the
once-a-second run sample misses the bad moment almost every time — and no driver status = this
device cannot answer the driver question at all). A session that lands on any other lane says so
in the log rather than faulting silently.
Note that PUNKTFUNK_AU_DUMP records the AU as it arrived from the HOST, while the fault injector
runs later, at the native decoder's own entry. On a faulted run the dump is therefore the clean
bitstream — reconstruct the damaged bytes from the spec if you need them (the injector is pure and
deterministic).