[FFmpeg-devel] [PATCH] aacenc_utils: unroll loops to allow compiler to use SIMD.

[Ganesh Ajjanagadde]

On Sun, Mar 6, 2016 at 1:43 PM, Reimar Döffinger
<Reimar.Doeffinger at gmx.de> wrote:
> On Sun, Mar 06, 2016 at 07:35:58PM +0100, Reimar Döffinger wrote:
>> Approximately 10% faster transcode from mp3 to aac
>> with default settings.
>
> Note to anyone wanting to optimize it further:
> There is almost 25% on the table if you can replace
> the pow() and cos() function uses by something more
> efficient.

So I did try one thing, namely in lavc/aacenc_utils, replace powf in
find_form_factor by a conditional checking for 2.0f, squaring if it
is, powf otherwise (see lavc/aaccoder_twoloop for the calls, one is
with 2.0f, other without), but it yields essentially nothing.

Likewise, an even more trivial one is line 125 of aaccoder_twoloop:
powf can be replaced here by sqrtf(sqrtf()), but this also yields
nothing.

Can you be more specific, and are you sure about this?

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