The signal remains digital, but decompressed into a raw bitstream that would be many mbps (think how big lossless filesizes get). So it has to be re-encoded but

The signal remains digital, but decompressed into a raw bitstream that would be many mbps (think how big lossless filesizes get). So it has to be re-encoded but you’re doubling the compression artefacts, and can only avoid them by really dialing up the bitrate. Maybe someone made a video encoder algorithm that’s tuned toward already compressed and decompressed video. Though I’m in the camp of watching for quality of the story etc. rather than the crispness of the video. If it’s not worth watching in 480p, it’s not worth watching in 4K either.