[FFmpeg-devel] [PATCH] lavfi/af_compensationdelay: replace pow(x, 0.5) by sqrt(x)

Paul B Mahol onemda at gmail.com
Tue Jan 5 11:40:48 CET 2016


On 1/5/16, Ganesh Ajjanagadde <gajjanagadde at gmail.com> wrote:
> sqrt is faster, and is sometimes more accurate depending on the libm.
>
> Signed-off-by: Ganesh Ajjanagadde <gajjanagadde at gmail.com>
> ---
>  libavfilter/af_compensationdelay.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/libavfilter/af_compensationdelay.c
> b/libavfilter/af_compensationdelay.c
> index 33ee7e4..d5a3484 100644
> --- a/libavfilter/af_compensationdelay.c
> +++ b/libavfilter/af_compensationdelay.c
> @@ -57,7 +57,7 @@ AVFILTER_DEFINE_CLASS(compensationdelay);
>  // The maximum distance for options
>  #define COMP_DELAY_MAX_DISTANCE            (100.0 * 100.0 + 100.0 * 1.0 +
> 1.0)
>  // The actual speed of sound in normal conditions
> -#define COMP_DELAY_SOUND_SPEED_KM_H(temp)  1.85325 * (643.95 * pow(((temp +
> 273.15) / 273.15), 0.5))
> +#define COMP_DELAY_SOUND_SPEED_KM_H(temp)  1.85325 * (643.95 * sqrt(((temp
> + 273.15) / 273.15)))
>  #define COMP_DELAY_SOUND_SPEED_CM_S(temp)
> (COMP_DELAY_SOUND_SPEED_KM_H(temp) * (1000.0 * 100.0) /* cm/km */ / (60.0 *
> 60.0) /* s/h */)
>  #define COMP_DELAY_SOUND_FRONT_DELAY(temp) (1.0 /
> COMP_DELAY_SOUND_SPEED_CM_S(temp))
>  // The maximum delay may be reached by this filter
> --
> 2.6.4
>
> _______________________________________________
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> ffmpeg-devel at ffmpeg.org
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>

ok


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