How does converting video to 4K actually work?
Upscaling a video to 4K means algorithmically generating millions of new pixels using interpolation or AI, since the extra detail was never actually recorded. The outcome can look convincing, but it will never be a true match for genuine 4K footage.
4K, or ultra-high-definition video, contains 3,840 x 2,160 pixels per frame, compared to 1,920 x 1,080 pixels for 1080p. Converting 1080p footage to 4K means adding three new pixels for every one that was originally recorded — quadrupling the total pixel count. That missing information can't simply be recovered; software can only estimate it.
Interpolation versus AI
Traditional upscaling software relies on interpolation, using mathematical calculations based on the color and brightness of surrounding pixels to predict new ones. This approach produces fairly predictable results but often looks softer, since it can't recreate genuine texture or detail. Newer AI-based tools are trained on pairs of low- and high-resolution images, allowing them to predict what a sharper version of an image should look like. AI upscaling tends to produce more convincing results, though it can introduce unusual artifacts that interpolation doesn't.
Source quality matters most
Professionals restoring footage to 4K try to work from the best original source material available. The remastering of Star Trek: The Next Generation, for example, used the show's original 35mm film negatives — with quality equivalent to roughly 20 megapixels — to upgrade the series for Blu-ray. Commissioned by CBS in 2011, the project used 25,000 reels of film stock, took more than three years, and reportedly cost over $12 million, according to one producer.
Home users rarely have access to such resources, so results depend heavily on the quality of the original file. If the source material is already low resolution or heavily compressed, upscaling can't recover lost detail — the missing pixels are simply guessed. Older footage recorded with interlacing also needs to be de-interlaced before upscaling. In general, the smaller the jump in resolution, the better the final result will look.
