---
title: PyroWave (wired-LAN codec)
description: The opt-in ultra-low-latency wavelet codec for wired links — what it is, the bandwidth it needs, and how to turn it on.
---

PyroWave is an **opt-in** video codec mode for links that can afford real bandwidth: wired
Ethernet, a docked Steam Deck, a 2.5GbE LAN. It trades bitrate for latency — instead of
H.264/HEVC/AV1 on the GPU's video engine, frames are compressed with
[PyroWave](https://github.com/Themaister/pyrowave), an intra-only wavelet codec running as plain
Vulkan compute. Punktfunk vendors a pinned copy and runs it on both ends.

**It is never selected automatically.** HEVC/AV1 remain the codecs for Wi-Fi and everything
else; PyroWave engages only when *you* pick it on the client **and** the host supports it. If
either side can't, the session silently falls back to the normal codec ladder.

## Why you'd want it

- **Codec latency drops by an order of magnitude.** Encode and decode each take a fraction of a
  millisecond of GPU compute (measured ~0.15 ms encode / ~0.07 ms decode at 1080p on an
  RTX 5070 Ti), versus one-to-several milliseconds per side for the hardware H.26x pipelines.
- **Every frame is a keyframe.** There is no GOP, no reference chain, no keyframe round-trip
  after packet loss — a lost frame costs exactly that frame, and the next one is already a
  complete picture. The whole IDR/recovery apparatus that produces loss-time stutter simply
  doesn't exist in this mode.
- **Uniform frame sizes.** The rate control hits its per-frame byte budget exactly, so the
  pacer sees a flat load instead of 20–40× keyframe spikes.

## What it costs

Bandwidth. At the codec's ~1.6 bits-per-pixel operating point (4:2:0, SDR):

| Mode | Bitrate |
|---|---|
| 1280×800 @ 60 (Deck) | ≈ 100 Mbps |
| 1920×1080 @ 60 | ≈ 200 Mbps |
| 1920×1080 @ 120 | ≈ 400 Mbps |
| 2560×1440 @ 60 | ≈ 355 Mbps |
| 2560×1440 @ 120 | ≈ 710 Mbps |
| 3840×2160 @ 60 | ≈ 800 Mbps |
| 3840×2160 @ 120 | ≈ 1.6 Gbps |

Frame rate scales the rate linearly, [4:4:4](#444-and-hdr) multiplies it by ~1.6, and an
[HDR](#444-and-hdr) (10-bit) session adds ~15 %. Estimate any combination:

<BitrateCalculator />

Gigabit Ethernet tops out around 940 Mbps of payload, so 4K60 wants 2.5GbE and the big
4:4:4 / HDR / high-refresh modes want 5GbE or 10GbE. **Do not run this over Wi-Fi** — that's
what HEVC/AV1 are for.

## 4:4:4 and HDR

PyroWave carries **full-chroma 4:4:4** and **HDR** the same way it carries everything else —
intra-only, every frame a keyframe — so the low-latency and clean-loss properties above hold
in these modes too. Both are negotiated per session from your client's settings, exactly like
HEVC/AV1; nothing PyroWave-specific to turn on beyond picking the codec.

- **4:4:4 (full chroma).** With your client's **4:4:4** setting on, the session encodes chroma
  at full resolution instead of subsampled 4:2:0 — sharp coloured text, thin UI lines, and
  red/blue edges that 4:2:0 softens. It costs ~1.6× the bitrate (chroma compresses better than
  luma, so it is less than the 2× the extra samples imply). Available on Linux and Windows
  hosts.
- **HDR (10-bit, BT.2020 PQ).** With HDR on, the session carries the 10-bit BT.2020 PQ signal in
  16-bit planes and adds ~15 % to the bitrate. **PyroWave HDR needs a Windows host today** — the
  Linux PyroWave path has no HDR colour conversion, so a Linux-hosted PyroWave session is SDR; stay
  on HEVC or AV1 for HDR from Linux, where PyroWave is the odd one out among the
  [codec rules](/docs/hdr#codec-rules). 4:4:4 works with PyroWave on both.
- The two combine: a 4:4:4 **and** HDR session applies both factors (~1.6 × 1.15 ≈ 1.9× the
  4:2:0 SDR rate). The Apple and Rust clients decode whatever the session negotiated — 4:2:0
  or 4:4:4, SDR or HDR — with no extra setup.

At the top end this gets demanding: 4:4:4 + HDR at a super-ultrawide 5120×1440@240 pins around
5.3 Gbps, which is more than a 5GbE link carries. On a link that can't keep up, either set an
explicit lower bitrate on the client or cap the host's Automatic pin with
[`PUNKTFUNK_PYROWAVE_MAX_MBPS`](/docs/configuration) — otherwise the overshoot just becomes
dropped packets.

## Turning it on

1. **Host** (Linux): nothing to do — default builds ship the codec and every Linux GPU host
   advertises it. AMD, Intel and NVIDIA hosts all encode straight from the capture dmabuf: the
   wavelet encoder owns its own Vulkan device and imports the buffer on any vendor, so there is
   no CPU copy on the host. (A compositor that refuses every offered dmabuf format still falls
   back to the CPU path, as it does for the other codecs.)
2. **Client**:
   - Linux client: set **Settings → Video codec → PyroWave (wired LAN)** — the same setting in
     the GTK desktop app and in the full-screen controller UI. Or launch with
     `PUNKTFUNK_PREFER_PYROWAVE=1`.
   - Windows client: set **Settings → Video codec → PyroWave (wired LAN)** (Intel, AMD and
     NVIDIA alike; x64 only — the ARM64 build does not include the decoder).
   - Apple (Mac, Apple TV 4K, iPad — wired networking strongly recommended): set
     **Settings → Codec → PyroWave (wired LAN)**. The option appears only on devices whose
     GPU passes the decode probe (Apple Silicon and A13-class or newer). The decoder follows
     the stream: 4:2:0 or 4:4:4, SDR or HDR, per what the session negotiated.
3. Leave the bitrate on Automatic: a PyroWave session pins itself to the ~1.6 bpp rate for
   your mode (≈200 Mbps at 1080p60; ~2.6 bpp for 4:4:4, +15 % for HDR). An explicit bitrate is honored if you set one, but the
   adaptive-bitrate controller stays off either way — this codec has no useful low-rate
   regime, so under sustained loss the right move is switching back to HEVC, not degrading.
   The pin follows the resolution: a mid-stream resize (e.g. Match window) re-pins the rate
   for the new mode, so resizing a window down also cuts the bandwidth.

The stats overlay shows `pyrowave` as the decode path when the mode is active.

## Checking the host is really zero-copy

On a Linux host the CPU fallback mentioned above is not an error — the session still streams, it
just pays a full-resolution copy of every frame, which shows up as a lower frame-rate ceiling and
higher CPU use rather than as anything obviously broken. The host log states which path a session
took, once, when the capture starts:

```
capture pipeline resolved: dmabuf-passthrough → pyrowave
```

`dmabuf-passthrough` is the good one: the compositor's buffer goes straight into the wavelet
encoder. `cpu` means the copy is happening, and a second line says why — a compositor that would
not allocate a dmabuf, `PUNKTFUNK_ZEROCOPY` set to `0`, or a per-frame fall-through such as the
compositor serving shared memory after agreeing to dmabufs. Each distinct reason is logged once per
session with a running count, so a persistent downgrade is easy to tell from a hiccup while the
display mode settles.

If you see `cpu` and did not ask for it, check that `PUNKTFUNK_ZEROCOPY` is unset (it defaults to
on) and read the accompanying line — it names the cause and the fix.

## Current limits

- Linux and Windows hosts; Linux clients (the GTK desktop app and the session client, including
  a docked Deck), the Windows client on x64, and Apple clients (native Metal decode on Mac, and on
  A13-or-newer iPhone, iPad and Apple TV hardware) today. Android has no PyroWave decoder.
- **PyroWave HDR needs a Windows host today** — a Linux-hosted PyroWave session is SDR, however the
  rest of the box is set up (see [4:4:4 and HDR](#444-and-hdr) above). 4:4:4 works on both.
