Static kVTCompressionPropertyKey_UsingGPURegistryID 

pub unsafe static kVTCompressionPropertyKey_UsingGPURegistryID: &'static CFString

Available on crate feature VTCompressionProperties only.

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

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

See also Apple’s documentation