Hi each stream has one global header in nut, matroska and avi too have exactly one global header APIs like the ones from mplayer and ffmpeg and directshow AFAIK are also designed based on a single global header but a very small number of codecs are designed so that they have several global headers but no standarized way (that i know of) of converting them to a single header, the "ogg codecs" fall in this category several solutions exist: 1. store several headers at nut level 2. leave it unspecified 3. specify how these multi packet codecs should be stored be it in nut.txt or in a seperate file if we do specify how these codecs should be stored then we can either A. invent our own system (this is for all practical proposes is identical to storing them at nut level) B. borrow the system from another container format leaving it unspecified will lead to a mess of different systems used by different muxers storing them at nut level will need them to be converted to a single packet format during demuxing and to a multi packet format during nut muxing in most cases borrowing another system and using that throughout an application will lead to the least converting around -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB In the past you could go to a library and read, borrow or copy any book Today you'd get arrested for mere telling someone where the library is