Y4M to JPG Converter

Y4M (YUV4MPEG2) is uncompressed video with a one-line text header: resolution, framerate and color space, then raw YUV frames. It is the lingua franca of video-filter pipelines — AviSynth, Vapoursynth and encoder test suites pass frames around as Y4M because there is nothing to misparse.

A Y4M of any real length is enormous (30MB per second of 1080p), so conversion to MP4/WEBM with H.264 or VP9 is always the destination — the value is in the zero-ambiguity input, not the format itself.

JPG (short for JPEG, the Joint Photographic Experts Group committee that standardized it in 1992) has been the default photo format for over three decades. It compresses photographs using the discrete cosine transform: the image is split into 8×8 blocks, and details the human eye is bad at noticing are discarded. The result is files many times smaller than uncompressed data, at a quality level you control when saving.

In practice JPG is unbeatable for photographs and smooth gradients — camera memory cards, messaging apps and the web all assume it. It is a poor fit for screenshots, logos or anything with sharp edges and flat color, where compression leaves visible ringing around text. There is no transparency support, color depth is capped at 8 bits per channel, and every re-save with compression compounds tiny generational losses.