[FFmpeg-devel] [PATCH] libavutil: add an FFT & MDCT implementation

[Lynne]

May 6, 2019, 11:41 PM by barsnick at gmx.net:

> On Mon, May 06, 2019 at 02:23:26 +0200, Lynne wrote:
>
>> This allowed for the exptabs to be computed just once on startup and
>> stored in a global array.
>>
>
> I have no real understanding of this, but:
> Would there be a desire for a static implementation as well, for those
> using "-enable-hardcoded-tables" (CONFIG_HARDCODED_TABLES)? Just
> wondering whether that's esoteric, optional, or really nice to have.
>
> Moritz
>

Not really, its just nicer, saves 64 bytes per context and some time on subsequent inits,
and might help with SIMD because more can be hardcoded into the assembly.
I don't think the hardcoded tables flag helps much nowadays, binary size seems more
important to users shipping the libraries. Also it might improve precision somewhat
for floats if the compiling machine has a different libc than the user's machine, and the
sin/cos approximations used on the compiling machine's libc are worse.