are you saying that if you metaflac --import-picture-from several large pictures, that it will rewrite the file for each picture addition? it's written to only rewrite the file once after all ops have been processed. No, I meant that to avoid such long command lines I would like to add every image separately (in a batch file) - after adding sufficient padding first. But even with several times the amount of padding needed (e.g. after adding it while encoding with flac.exe - which seems to allow bigger paddings) metaflac still rewrites the file even when there is more than enough padding left. It seems to me that not only metaflac can't add such large paddings but either that flac.exe also has a problem with them (without saying so) or that metaflac can't even utilize pre-existing large paddings.I can see the problem with commandline-length limitations. I don't know why the windows limit is so small. on practically every other modern OS this is not a problem. Microsoft commented on this problem here . Don't know about Vista but I doubt that this has changed. What else would you expect from the "640 Kilobyte ought to be enough for anybody "-company. I think it would be great if an option could be added to (meta)flac which allows to read other parameters from a text file:flac.exe --parameter-from-file=<FILE> <INPUTFILE> This would certainly solve my problem by eliminating the need for huge paddings (although if those would work it would be cool, too ).