special audio in AVI demuxer

1. VFR audio - Vorbis in AVI

 

FFMPEG is using the second idea. However, ffmpeg is increasing the overhead even more, as
it stores frame headers for each of the padding chunks, wasting 8 bytes each time, instead of
only storing one of them physically, adding an index entry everytime such a chunk is required,
and setting AVIF_MUSTUSEINDEX. For such streams, the following ID is used: wFormatTag
= 0x566F. The Vorbis initialization packets (the first 3 packets of an OGG/Vorbis file) are
stored as private data in the strf chunk. Each vorbis initialization packet is stored the
following way:

                big_endian_int16 size
                char data[size];