In video and audio signal processing, it is often necessary to take a set of sample values and produce another set that approximates the samples that would have resulted had the original sampling occurred at different instants – at a different rate, or at a different phase. This is called resampling. (In PC parlance, resampling for the purpose of picture resizing is called scaling.) Resampling is an essential part of video processes such as these:
• Chroma subsampling (e.g., 4:4:4 to 4:2:2)
• Downconversion (e.g., HD to SD) and upconversion (e.g., SD to HD)
• Aspect ratio conversion (e.g., 4:3 to 16:9)
• Conversion among different sample rates of digital video standards (e.g., 4f SC to 4:2:2, 13.5 ...