Farbsampling

Farbsampling, also known as chroma subsampling, is the process of reducing the resolution of color information in digital images and video relative to luminance. It relies on the human visual system’s higher sensitivity to brightness than to color, allowing significant data savings with limited perceptual loss.

The method uses color spaces such as YCbCr, where Y represents luma (brightness) and Cb and Cr are chroma (blue-difference and red-difference) components. Subsampling specifies how many chroma samples are taken for each set of luma samples, commonly denoted in 4:x:y notation. The main schemes are 4:4:4 (no chroma subsampling), 4:2:2 (half horizontal chroma resolution), and 4:2:0 (half horizontal and vertical chroma resolution). Some standards also use 4:1:1. In practice, 4:2:0 is widely used for video delivery and consumer formats.

Applications include video compression and distribution (formats such as MPEG-2, H.264/AVC, H.265/HEVC, AV1), streaming, and broadcast. Still-image formats like JPEG also employ chroma subsampling, typically at 4:2:0 for many applications. In professional workflows, 4:2:2 or 4:4:4 may be used to preserve color fidelity.

Processing considerations involve encoding and decoding: chroma channels are subsampled for storage and bandwidth savings, then upsampled during playback, which can introduce artifacts if upsampling is aggressive or the content contains fine color detail. The choice of subsampling scheme, color space, and bit depth influences the balance between data rate and visual quality. Farbsampling remains a fundamental technique in modern digital media.