[FFmpeg-devel] [PATCH] avfilter: add audio emphasis filter

[Ganesh Ajjanagadde]

On Thu, Dec 3, 2015 at 5:52 PM, Paul B Mahol <onemda at gmail.com> wrote:
> Signed-off-by: Paul B Mahol <onemda at gmail.com>
> ---
>  Changelog                  |   1 +
>  configure                  |  26 ++++
>  doc/filters.texi           |  46 ++++++
>  libavfilter/Makefile       |   1 +
>  libavfilter/af_aemphasis.c | 370 +++++++++++++++++++++++++++++++++++++++++++++
>  libavfilter/allfilters.c   |   1 +
>  libavfilter/version.h      |   2 +-
>  7 files changed, 446 insertions(+), 1 deletion(-)
>  create mode 100644 libavfilter/af_aemphasis.c
>
> diff --git a/Changelog b/Changelog
> index 2d2a92b..552fab1 100644
> --- a/Changelog
> +++ b/Changelog
> @@ -39,6 +39,7 @@ version <next>:
>  - support encoding 16-bit RLE SGI images
>  - apulsator filter
>  - sidechaingate audio filter
> +- aemphasis filter
>
>
>  version 2.8:
> diff --git a/configure b/configure
> index a30d831..10631e8 100755
> --- a/configure
> +++ b/configure
> @@ -1051,6 +1051,21 @@ int main(void){ $func(); }
>  EOF
>  }
>
> +check_complexfunc(){
> +    log check_complexfunc "$@"
> +    func=$1
> +    narg=$2
> +    shift 2
> +    test $narg = 2 && args="f, g" || args="f"
> +    disable $func
> +    check_ld "cc" "$@" <<EOF && enable $func
> +#include <complex.h>
> +#include <math.h>
> +float foo(complex float f, complex float g) { return $func($args); }
> +int main(void){ return (int) foo; }
> +EOF
> +}
> +
>  check_mathfunc(){
>      log check_mathfunc "$@"
>      func=$1
> @@ -1768,6 +1783,11 @@ INTRINSICS_LIST="
>      intrinsics_neon
>  "
>
> +COMPLEX_FUNCS="
> +    cabs
> +    cexp
> +"
> +

These are not inherently needed, cabs and cexp can be easily
implemented using hypot and sin, cos, etc. See e.g the mandelbrot
filter; the filter mathematically operates on complex numbers, but one
can always use the real value variants with a trivial amount of work.

Don't know and it is unlikely that all our platforms have them - a
platform which refuses to implement simple things like llrint would
most likely not bother with this stuff. If you really want to use
complex numbers (though above demonstrates there is no inherent
reason), you should add the relevant compat hacks.

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