Vulkan 1.4.366 adds SMPTE ST 2094-50 dynamic HDR metadata

The Khronos Group published version 1.4.366 of the Vulkan specification on October 23, 2026. Its one new feature is a Google extension that lets an app attach SMPTE ST 2094-50 dynamic HDR metadata to the images it shows on screen. That gives Vulkan programs a standard way to tell a display how to adjust bright HDR video scene by scene, instead of with one fixed setting.

Vulkan is the open graphics interface that games, video players and browsers use to talk to the graphics chip. The Khronos Group is the industry body that maintains it. Small specification updates arrive about every two weeks, and the last number in the version counts them. The last one we covered, 1.4.363, added an Intel hardware query.

What the new extension does

The extension is listed in the Khronos changelog as VK_GOOGLE_hdr_SMPTE_ST_2094_50_metadata. Its specification files spell it VK_GOOGLE_hdr_smpte_st_209450_metadata. It attaches to the swapchain, the queue of finished frames waiting to go to the screen.

HDR, or high dynamic range, means video with much brighter highlights than standard video. Displays differ widely in how bright they can go. The spare brightness a screen has above normal white is called its headroom. Software has to squeeze HDR video to fit each screen, a step called tone mapping.

Until now Vulkan only offered static HDR metadata, through the older VK_EXT_hdr_metadata extension. Static metadata describes a whole video once. Dynamic metadata can change from scene to scene. The new extension fills that gap, according to its proposal document.

The pieces it adds are small.

Name	What it is for
VkHdrSmpteSt209450GOOGLE	Carries the metadata: a size, a pointer to the ST 2094-50 data, and a power preference
VkPhysicalDeviceHdrSmpteSt209450FeaturesGOOGLE	Reports whether the device supports the feature
VkSurfaceCapabilitiesHdrSmpteSt209450GOOGLE	Reports whether a given window surface supports it
VkHdrSmpteSt209450PowerPreferenceGOOGLE	Picks color accuracy (0) or low power (1)

The metadata structure chains onto the existing VkHdrMetadataEXT structure. The proposal says that design copies Huawei's earlier VK_HUAWEI_hdr_vivid extension. It also requires VK_EXT_hdr_metadata and VK_KHR_get_surface_capabilities2.

The extension's appendix credits three Google engineers: Alec Mouri, Christopher Cameron and John Reck. It is at revision 1, dated October 8, 2026.

What SMPTE ST 2094-50 is

SMPTE is the standards body for film and TV engineering. ST 2094-50 is its new standard for mixing HDR and standard content on one screen. Google developed it with Apple and NBCUniversal, according to a May 14, 2026 Google blog post.

The problem it targets is familiar. Mixed HDR and standard content can look "washed-out or blown-out," Google wrote. The standard uses two tools. A reference white anchor pins standard content to a fixed brightness. Headroom-adaptive gain curves, written by the video's creator, then tell a dim screen how to compress shadows and midtones while keeping highlights.

Phoronix reports the standard was finalized in August. Google said in May that support for the finalized standard is coming to an upcoming Chrome release, without naming a version.

The fixes in 1.4.366

The changelog lists five fixes from public GitHub reports and 11 from Khronos' internal tracker. A few are worth knowing:

• An off-by-one error in valid-usage rule 08071, for binding descriptor buffers, was corrected.
• A new rule requires unique address ranges when writing descriptors with vkWriteSamplerDescriptorsEXT and vkWriteResourceDescriptorsEXT.
• Swapped HLSL mappings in the VK_EXT_ray_tracing_invocation_reorder proposal were fixed.
• The tooling's base image was updated for a certificate problem involving eMudhra, the certificate authority that recently left the public certificate business.
• Driver IDs for two drivers, nikki and momoten, were registered.

What this means for developers

Most game developers can skip this release. It matters to teams that play HDR video through Vulkan: video players, browsers, compositors and Android media apps.

If that is you, check support before using it. Query the device feature, then the surface capability, since a vendor-prefixed extension only exists where a driver exposes it.

Treat the metadata buffer with care. The proposal says the implementation will not validate the contents of pMetadata and passes it straight to the display engine. A malformed bitstream will not raise a Vulkan error, so test with real ST 2094-50 content.

Choose the power mode on purpose. Laptops and phones may prefer low power, while editing tools want color accuracy.

Finally, do not expect a headroom query yet. The proposal says a separate extension for querying and limiting a swapchain's headroom "may be more appropriate." Watch for that, and for which Chrome release ships ST 2094-50 support.