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

[Jimmy Christensen]

On 2009-06-30 15:50, Reimar D?ffinger wrote:
> On Tue, Jun 30, 2009 at 03:09:33PM +0200, Jimmy Christensen wrote:
>>> Lastly it seems to me that this code would belong into
>>> libavutil/intfloat_readwrite.*
>>
>> You are probably right.
>
> Personally I'd suggest doing a stupid implementation for
> libavutil/intfloat_readwrite.*, something like this (certainly
> not a beauty, possibly buggy, does not support denormals, though since
> they are rare it probably wouldn't be a big issue to add handling for
> them in if (nosign<  0x0400)).
> float av_int2halflt(int16_t v){
>      uint16_t nosign = v+v;
>      if (nosign>= 0xfc00) {
>          if (nosign == 0xfc00) return v>>15 ? -1.0/0.0 : 1.0/0.0;
>          else return 0.0/0.0;
>      }
>      if (nosign<  0x0400) return 0; // denormal or 0
>      return ldexp((v&0x3ff) + (1<<11)) * (v>>15|1), (v>>10&0x1f)-26);
> }
>
>
> And consider an optimized version only after it is actually used and
> thus it is clear what kind of optimizations are necessary/most useful.
> E.g. the table based approach probably is hard to SIMD and thus might be
> a bad idea if you want to convert a lot of data.

So I should just put the table into the OpenEXR decoder (eg. disabled by 
default)?

-- 
Best Regards
Jimmy Christensen
Developer
Ghost A/S