Function nvjpeg_available 

pub fn nvjpeg_available() -> bool

Returns true when the nvJPEG GPU JPEG decoder is available at runtime — Linux with CUDA + libnvjpeg loaded and opted in via EDGEFIRST_ENABLE_NVJPEG (off by default, so it never silently contends with CUDA inference). When true the codec prefers it over the V4L2/CPU backends for CUDA-backed destinations. Always false on other platforms or when the nvjpeg feature is disabled. Useful for benchmarks and consumers that branch on backend availability.