[FFmpeg-soc] BFI

[Sisir Koppaka]

On Sat, Mar 22, 2008 at 2:03 AM, Mike Melanson <mike at multimedia.cx> wrote:

> Sisir Koppaka wrote:
> > The BFI wiki page says(http://wiki.multimedia.cx/index.php?title=BFI) :
> >
> >  bytes 60-827   ( +3C) 256 RGB triplets (6-bit VGA palette values)
> >
> >  and also,
> > The video always encoded as palettized, 8-bit data.
> >
> > How are these two the same? Yes, 8 bit data corresponds to 256 RGB
> triplets
> > but what is the '6-bit VGA palette values'? I'm finding some trouble
> here
> > handling the decoding, can anyone please help me with this?
>
> A decoded picture is width x height pixels. Each pixel is 8 bits, or 1
> byte. That's where the "8-bit data" part comes from.
>
> There is a 256-color palette. Each pixel (which is an 8-bit value,
> 0-255) points to one of those 256 colors. Each color is comprised of a
> red, green, and blue value. Each R, G, and B value has a 6-bit range
> (0-63). That's where the "6-bit VGA palette values" part comes from.
> More background on that here:

But the size of the BFI palette is 256*3 right? Did you mean to say that
there is a 256-color palette for R, G and B individually? In that case,
wouldn't R,G and B have a depth of 256 instead of 64?  Also, I'm setting the
palette once in the demuxer? How often do we have to set the palette? like
for every frame in the decoder?

-----------------
Sisir Koppaka