Static kVTDecompressionPropertyKey_UsingGPURegistryID 

pub unsafe static kVTDecompressionPropertyKey_UsingGPURegistryID: &'static CFString

Available on crate feature VTDecompressionProperties only.

returns CFNumber indicating the gpu registryID of the decoder that was selected. NULL indicates a built-in decoder or software decode was used.

You can query this property using VTSessionCopyProperty after building a VTDecompressionSession to find out which GPU the decoder is using. If a decoder based on a built-in GPU was used it will return NULL. If a software decoder is used, it will return NULL

See also Apple’s documentation