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

Jimmy Christensen jimmy
Tue Jun 30 10:07:16 CEST 2009

On 2009-06-30 10:01, M?ns Rullg?rd wrote:
> 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
> functionality.

I don't have access to any ARM NEON processors. How should I proceed 
with this?

>> 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
> rescaling.

Hehe. Was just a simple copy/paste from a previous header :) Will remove 
the copyright. I just asked for permission of pure politeness.

Best Regards
Jimmy Christensen
Ghost A/S

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