feat(linux/vulkan-encode): default-on native NV12 capture + RGB true-extent

Flip both zero-copy levers from opt-in to default:

- The capture negotiation now PREFERS gamescope's producer-side NV12 pod by
  default (PUNKTFUNK_PIPEWIRE_NV12=0 restores the packed-RGB negotiation).
  Codec-aware gating rides a new OutputFormat::nv12_native ->
  ZeroCopyPolicy::native_nv12_session edge resolved by the host facade from
  the session plan (pf_encode::linux_native_nv12_ok): only H265/AV1 sessions
  whose backend can open the raw Vulkan Video encoder ever see the NV12 pod
  -- an H264/Moonlight session (libav VAAPI, which would misread the
  two-plane buffer) keeps today's BGRx negotiation, as do the
  GameStream-resolve and portal-mirror paths, PyroWave, and NVENC prefs.
- RGB-direct's unaligned modes default to the true-extent direct import
  (PUNKTFUNK_VULKAN_RGB_TRUE_EXTENT=0 restores the padded-copy staging).
  Guarded-tested on Van Gogh with the kernel journal watched: clean, and at
  5.38 ms p50 the fastest 1080p encode path measured on that hardware. The
  EFC only exists on Mesa >= 26, where the codedExtent-driven session_init
  padding is guaranteed (verified back to Mesa 24.2).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

crates/pf-encode/src/enc/linux/vulkan_video.rs

@@ -84,13 +84,14 @@ fn rgb_request() -> Option<bool> {
     }
 }
 
-/// `PUNKTFUNK_VULKAN_RGB_TRUE_EXTENT=1` (bring-up): at unaligned modes, replace RGB-direct's
-/// padded-copy staging with a direct import carrying the TRUE-SIZE source `codedExtent` — RADV
-/// derives nonzero VCN firmware padding from it, so the EFC is told the source lacks the
-/// alignment rows (see [`RgbDirect::true_extent`]). Off by default until the EFC front-end is
-/// proven to honor the padding like the YUV fetch path does.
+/// True-extent RGB-direct at unaligned modes (default ON; `PUNKTFUNK_VULKAN_RGB_TRUE_EXTENT=0`
+/// restores the padded-copy staging): direct-import the visible-size capture with the TRUE-SIZE
+/// source `codedExtent` — RADV derives nonzero VCN firmware padding from it, so the EFC is told
+/// the source lacks the alignment rows (see [`RgbDirect::true_extent`]). Guarded-tested on Van
+/// Gogh 2026-07-21 (kernel clean, and the fastest 1080p encode path measured); the EFC only
+/// exists on Mesa ≥ 26, where the `codedExtent`-driven `session_init` is guaranteed.
 fn rgb_true_extent_request() -> bool {
-    std::env::var("PUNKTFUNK_VULKAN_RGB_TRUE_EXTENT").as_deref() == Ok("1")
+    std::env::var("PUNKTFUNK_VULKAN_RGB_TRUE_EXTENT").as_deref() != Ok("0")
 }
 
 /// Live RGB-direct session config: the chroma-siting bits the session was created with
@@ -105,13 +106,13 @@ struct RgbDirect {
     /// with the edge rows/columns duplicated into the padding (transfer-only, no shader) and
     /// encoded from there. Aligned modes keep the true zero-copy import.
     padded: bool,
-    /// `PUNKTFUNK_VULKAN_RGB_TRUE_EXTENT=1` bring-up alternative to `padded` at unaligned
-    /// modes: direct-import the visible-size buffer and pass the TRUE-SIZE source
+    /// The default unaligned-mode source strategy (`PUNKTFUNK_VULKAN_RGB_TRUE_EXTENT=0` falls
+    /// back to `padded`): direct-import the visible-size buffer and pass the TRUE-SIZE source
     /// `codedExtent` — RADV then programs nonzero firmware padding from it (Mesa ≥ 24.2
     /// derives `session_init` padding from `srcPictureResource.codedExtent`; see
     /// [`VulkanVideoEncoder::native_nv12`]), telling the VCN the source lacks the alignment
-    /// rows. The session/SPS/DPB stay app-aligned. Field-proven for YUV fetches; the EFC RGB
-    /// front-end honoring the padding is what this gate exists to prove.
+    /// rows, which the hardware edge-extends internally. The session/SPS/DPB stay app-aligned.
+    /// Guarded-tested on Van Gogh (kernel clean; fastest 1080p path measured).
     true_extent: bool,
 }
 
@@ -696,7 +697,7 @@ impl VulkanVideoEncoder {
                     ) =>
                         "active(true-extent: unaligned mode, direct import with the true-size \
                          source codedExtent — RADV firmware padding covers the alignment rows; \
-                         PUNKTFUNK_VULKAN_RGB_TRUE_EXTENT bring-up)",
+                         PUNKTFUNK_VULKAN_RGB_TRUE_EXTENT=0 restores the padded copy)",
                     (_, _, Some(RgbDirect { padded: false, .. })) => "active",
                     (_, _, Some(RgbDirect { padded: true, .. })) =>
                         "active(padded-copy: mode is not 64x16-aligned — staging blit + edge \

crates/pf-encode/src/lib.rs

@@ -351,8 +351,8 @@ fn open_video_backend(
                     Err(e) if format == PixelFormat::Nv12 => {
                         return Err(e.context(
                             "Vulkan Video open failed on a native-NV12 capture \
-                             (PUNKTFUNK_PIPEWIRE_NV12=1) — no VAAPI fallback exists; unset the \
-                             flag to restore the packed-RGB pipeline",
+                             — no VAAPI fallback exists; set PUNKTFUNK_PIPEWIRE_NV12=0 to \
+                             restore the packed-RGB negotiation",
                         ));
                     }
                     Err(e) => tracing::warn!(
@@ -365,10 +365,10 @@ fn open_video_backend(
             // PUNKTFUNK_VULKAN_ENCODE=0, or a build without the feature).
             if format == PixelFormat::Nv12 {
                 anyhow::bail!(
-                    "native NV12 capture (PUNKTFUNK_PIPEWIRE_NV12=1) requires the Vulkan Video \
-                     encoder (HEVC/AV1 session, --features vulkan-encode, \
-                     PUNKTFUNK_VULKAN_ENCODE not 0) — this session resolved to libav VAAPI; \
-                     unset the flag"
+                    "native NV12 capture requires the Vulkan Video encoder (HEVC/AV1 \
+                     session, --features vulkan-encode, PUNKTFUNK_VULKAN_ENCODE not 0) — this \
+                     session resolved to libav VAAPI; set PUNKTFUNK_PIPEWIRE_NV12=0 to restore \
+                     the packed-RGB negotiation"
                 );
             }
             vaapi::VaapiEncoder::open(
@@ -841,6 +841,33 @@ fn vulkan_encode_enabled() -> bool {
         .unwrap_or(true)
 }
 
+/// Whether THIS session's encoder can ingest a producer-native NV12 capture: only the raw
+/// Vulkan Video backend does (libav VAAPI would misread the two-plane buffer as packed RGB —
+/// [`open_video`] refuses the combination), so the session's codec must be one it encodes and
+/// the backend must be eligible to open. The host facade threads the verdict into the capture
+/// negotiation (`OutputFormat::nv12_native` → `ZeroCopyPolicy::native_nv12_session`), which
+/// then PREFERS gamescope's producer-side NV12 pod (default-on; `PUNKTFUNK_PIPEWIRE_NV12=0`
+/// escapes at the capture gate).
+#[cfg(target_os = "linux")]
+pub fn linux_native_nv12_ok(codec: Codec) -> bool {
+    #[cfg(feature = "vulkan-encode")]
+    {
+        matches!(codec, Codec::H265 | Codec::Av1)
+            && vulkan_encode_enabled()
+            // NVENC/PyroWave prefs never open the Vulkan Video backend; every other pref
+            // (auto/vaapi/amd/intel/vulkan) tries it first on AMD/Intel — see [`open_video`].
+            && !matches!(
+                pf_host_config::config().encoder_pref.as_str(),
+                "nvenc" | "nvidia" | "cuda" | "pyrowave"
+            )
+    }
+    #[cfg(not(feature = "vulkan-encode"))]
+    {
+        let _ = codec;
+        false
+    }
+}
+
 /// Cheap, side-effect-free NVIDIA-presence probe for the `auto` backend selector: the NVIDIA
 /// kernel driver exposes these device nodes, AMD/Intel boxes have neither. Deliberately does NOT
 /// create a CUDA context (that would allocate GPU state on every host that merely *might* be