[FFmpeg-devel] [PATCH 2/3] avcodec/aacsbr: Add comment about possibly optimization in sbr_dequant()

Ganesh Ajjanagadde gajjanag at mit.edu
Thu Nov 19 15:03:03 CET 2015


On Thu, Nov 19, 2015 at 8:17 AM, Michael Niedermayer <michaelni at gmx.at> wrote:
> From: Michael Niedermayer <michael at niedermayer.cc>
>
> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> ---
>  libavcodec/aacsbr.c |    1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/libavcodec/aacsbr.c b/libavcodec/aacsbr.c
> index d1e3a91..e014646 100644
> --- a/libavcodec/aacsbr.c
> +++ b/libavcodec/aacsbr.c
> @@ -73,6 +73,7 @@ static void sbr_dequant(SpectralBandReplication *sbr, int id_aac)
>  {
>      int k, e;
>      int ch;
> +    //TODO: Replace exp2f(0.5*x) by a LUT, the inputs are all integer and have a small range

Entirely possible I missed something, but exp2 gives 2^x, so if inputs
are integers, can't one simply do the necessary bit shifts and cast
implicitly to float?
I think what you meant was all inputs are half-integers or integers.

>
>      if (id_aac == TYPE_CPE && sbr->bs_coupling) {
>          float alpha      = sbr->data[0].bs_amp_res ?  1.0f :  0.5f;
> --
> 1.7.9.5
>
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