If I understand it right, some lossy codecs can be implemented in an idempotent (and still standard-compliant) way, so there would be no generational loss (in s

If I understand it right, some lossy codecs can be implemented in an idempotent (and still standard-compliant) way, so there would be no generational loss (in select specific cases, e.g. matched settings). I'm also aware that e.g. JPEG-XL can reencode JPEGs without generational loss, while still improving compression efficiency a bit. But I never looked too deep into the math.