There are ID3 tags used for MP3 and other files. Old players may not know about them and may misread their data as MPEG frames. To prevent this a tag may break

There are ID3 tags used for MP3 and other files. Old players may not know about them and may misread their data as MPEG frames. To prevent this a tag may break up sequences of 00 bytes with an FF byte. Or may not, because now most players are aware of tags. So there is a preference, at two levels, default and for a single tag. Not too hard to program, but rather unfriendly to a grammar-based approach. (Another example are checksums.)