[FFmpeg-devel] [PATCH] Fast half-float to float conversion

Måns Rullgård mans
Tue Jun 30 10:01:00 CEST 2009

Jimmy Christensen <jimmy at ghost.dk> writes:

> Hi,
> I'm almost done with my OpenEXR decoder, but since it can work in a
> half-float format I wanted a fast half-float to float conversion. I
> found one in the FOX toolkit which uses a table lookup. I didn't want
> the table lookup in the OpenEXR decoder only, since a few other
> formats can use half-floats aswell. So instead I submit the half-float
> to float first as a libavutil header.

ARM NEON has hardware support for half-precision floating point.  This
conversion should be done in a way that allows using such CPU-specific

> The code is derivative work from the FOX toolkit, but I have already
> asked permission to include it in the ffmpeg project, granted that I
> stated origin and a link to the paper describing the table lookup. The
> paper can be seen here :
> http://www.fox-toolkit.org/ftp/fasthalffloatconversion.pdf
> I have tested the code with the before mentioned OpenEXR decoder and
> it works as expected with half floats.

Those tables look trivial enough that I have a hard time seeing how
they could be covered by copyright at all.  It's just a simple

M?ns Rullg?rd
mans at mansr.com

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