If you need to align data in you AVI file you can add a 'JUNK' chunk. (This chunk is a standard RIFF type.) Applications reading these chunks will ignore their contents. Files played from CD-ROM can use these chunks to align data so they can be read more efficiently. You might want to use this chunk to align your data for the 2 kilobyte CD-ROM boundaries. The 'JUNK' chunk has the following form:
AVI Padding 'JUNK'
Byte data[]
As with any other RIFF files, all applications that read AVI files should ignore the non-AVI chunks that it does not recognize. Applications that read and write AVI files should preserve the non-AVI chunk when they save files they have loaded.