Preprocessingsteg

Preprocessingsteg is a term used in steganography to describe the practice of applying preprocessing transformations to a host medium before embedding a secret payload. The goal is to influence the embedding process to improve imperceptibility, increase payload capacity, or enhance resilience against steganalysis and subsequent transformations such as compression or resizing.

Although not standardized, the concept appears in research on embedding pipelines where the cover material undergoes preprocessing steps tailored to the domain (images, audio, video) and embedding scheme. Common techniques include color space conversion (for example RGB to YCbCr), resizing or downsampling, denoising or smoothing, histogram equalization, quantization, and controlled compression. The specifics depend on the cover type and the embedding method.

In an embedding workflow, preprocessing alters the cover prior to data hiding with the aim of shaping its statistical properties to mask embedded bits. Some approaches seek to suppress perceptual cues, others to create stable embedding regions that are robust to later processing. Benefits may include improved undetectability and resilience; risks include artifacts, data degradation, or patterns detectable by a savvy detector.

Evaluation uses perceptual quality metrics such as PSNR or SSIM, alongside payload capacity and steganalysis performance. Practical considerations include computational cost and compatibility with target platforms.

Related topics include steganography, steganalysis, and digital watermarking.