[vlc-devel] fourccodes, pixelformat and video formats

David Flynn davidf+nntp at woaf.net
Mon Oct 27 23:50:36 CET 2008

Question: What do you want fourccodes to represent?

For the most part they represent codec and for rawvideo, the pixel
packing format.  Unfortunately they sometimes represent a bit more
than that; and worse the 'bit more' is often ignored or wrong.

A recent patch attempted to deal with adding HDYC as a supported fourcc
for a black magic directshow filter.  I didn't like it due to an
incorrect/inaccurate comment, but this has made me think.  HDYC uses
the same pixel packing format as UYVY, except it uses different colour
primaries and matrixing.

Personally i dislike the fourcc describing information other than the
pixel packing format -- it is too often wrong.  I suggest that
information about primaries, matrixing, transfer function are stored
in the video_format_t struture, then keep to using UYVY and friends
as fourcc (ie, the dshow filter should call HDYC UYVY as far as vlc
is concerned).

Being able to represent colourspace information would actually be
useful in the longrun (eg correctly handling wide colour gamuts)



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