[FFmpeg-devel] [PATCH] lavfi: add earwax audio filter, ported from Sox

Michael Niedermayer michaelni at gmx.at
Tue Nov 1 03:23:51 CET 2011


On Tue, Nov 01, 2011 at 01:51:32AM +0100, Stefano Sabatini wrote:
> From: Mina Nagy Zaki <mnzaki at gmail.com>
> 
> Signed-off-by: Stefano Sabatini <stefasab at gmail.com>
> ---
>  doc/filters.texi         |   10 +++
>  libavfilter/Makefile     |    1 +
>  libavfilter/af_earwax.c  |  159 ++++++++++++++++++++++++++++++++++++++++++++++
>  libavfilter/allfilters.c |    1 +
>  4 files changed, 171 insertions(+), 0 deletions(-)
>  create mode 100644 libavfilter/af_earwax.c
> 
> diff --git a/doc/filters.texi b/doc/filters.texi
> index f282b18..7085ae1 100644
> --- a/doc/filters.texi
> +++ b/doc/filters.texi
> @@ -224,6 +224,16 @@ expressed in the form "[@var{c0} @var{c1} @var{c2} @var{c3} @var{c4} @var{c5}
>  @var{c6} @var{c7}]"
>  @end table
>  
> + at section earwax
> +
> +Make audio easier to listen to on headphones. Adds `cues' to 44.1kHz
> +stereo (i.e. audio CD format) audio so that when listened to on
> +headphones the stereo image is moved from inside your head (standard
> +for headphones) to outside and in front of the listener (standard for
> +speakers).
> +
> +Ported from SoX.
> +
>  @section ladspa
>  
>  Apply a LADSPA effect.
> diff --git a/libavfilter/Makefile b/libavfilter/Makefile
> index 040d565..583dd6d 100644
> --- a/libavfilter/Makefile
> +++ b/libavfilter/Makefile
> @@ -28,6 +28,7 @@ OBJS-$(CONFIG_AFORMAT_FILTER)                += af_aformat.o
>  OBJS-$(CONFIG_ANULL_FILTER)                  += af_anull.o
>  OBJS-$(CONFIG_ARESAMPLE_FILTER)              += af_aresample.o
>  OBJS-$(CONFIG_ASHOWINFO_FILTER)              += af_ashowinfo.o
> +OBJS-$(CONFIG_EARWAX_FILTER)                 += af_earwax.o
>  OBJS-$(CONFIG_LADSPA_FILTER)                 += af_ladspa.o
>  OBJS-$(CONFIG_SOX_FILTER)                    += af_sox.o
>  
> diff --git a/libavfilter/af_earwax.c b/libavfilter/af_earwax.c
> new file mode 100644
> index 0000000..21099e2
> --- /dev/null
> +++ b/libavfilter/af_earwax.c
> @@ -0,0 +1,159 @@
> +/*
> + * Copyright (c) 2011 Mina Nagy Zaki
> + * Copyright (c) 2000 Edward Beingessner And Sundry Contributors.
> + * This source code is freely redistributable and may be used for any purpose.
> + * This copyright notice must be maintained.  Edward Beingessner And Sundry
> + * Contributors are not responsible for the consequences of using this
> + * software.
> + *
> + * This file is part of FFmpeg.
> + *
> + * FFmpeg is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * FFmpeg is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with FFmpeg; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> + */
> +
> +/**
> + * @file
> + * Stereo Widening Effect. Adds audio cues to move stereo image in
> + * front of the listener. Adapted from the libsox earwax effect.
> + */
> +
> +#include "libavutil/audioconvert.h"
> +#include "avfilter.h"
> +
> +#define NUMTAPS 64
> +
> +static const int8_t filt[NUMTAPS] = {
> +/* 30°  330° */
> +    4,   -6,     /* 32 tap stereo FIR filter. */
> +    4,  -11,     /* One side filters as if the */
> +   -1,   -5,     /* signal was from 30 degrees */
> +    3,    3,     /* from the ear, the other as */
> +   -2,    5,     /* if 330 degrees. */
> +   -5,    0,
> +    9,    1,
> +    6,    3,     /*                         Input                         */
> +   -4,   -1,     /*                   Left         Right                  */
> +   -5,   -3,     /*                __________   __________                */
> +   -2,   -5,     /*               |          | |          |               */
> +   -7,    1,     /*           .---|  Hh,0(f) | |  Hh,0(f) |---.           */
> +    6,   -7,     /*          /    |__________| |__________|    \          */
> +   30,  -29,     /*         /                \ /                \         */
> +   12,   -3,     /*        /                  X                  \        */
> +  -11,    4,     /*       /                  / \                  \       */
> +   -3,    7,     /*  ____V_____   __________V   V__________   _____V____  */
> +  -20,   23,     /* |          | |          |   |          | |          | */
> +    2,    0,     /* | Hh,30(f) | | Hh,330(f)|   | Hh,330(f)| | Hh,30(f) | */
> +    1,   -6,     /* |__________| |__________|   |__________| |__________| */
> +  -14,   -5,     /*      \     ___      /           \      ___     /      */
> +   15,  -18,     /*       \   /   \    /    _____    \    /   \   /       */
> +    6,    7,     /*        `->| + |<--'    /     \    `-->| + |<-'        */
> +   15,  -10,     /*           \___/      _/       \_      \___/           */
> +  -14,   22,     /*               \     / \       / \     /               */
> +   -7,   -2,     /*                `--->| |       | |<---'                */
> +   -4,    9,     /*                     \_/       \_/                     */
> +    6,  -12,     /*                                                       */
> +    6,   -6,     /*                       Headphones                      */
> +    0,  -11,
> +    0,   -5,
> +    4,    0};
> +
> +typedef struct {
> +    int16_t taps[NUMTAPS * 2];
> +} EarwaxContext;
> +
> +static int query_formats(AVFilterContext *ctx)
> +{
> +    AVFilterFormats *formats = NULL;
> +    avfilter_add_format(&formats, AV_SAMPLE_FMT_S16);
> +    avfilter_set_common_sample_formats(ctx, formats);
> +    formats = NULL;
> +    avfilter_add_format(&formats, AV_CH_LAYOUT_STEREO);
> +    avfilter_set_common_channel_layouts(ctx, formats);
> +    formats = NULL;
> +    avfilter_add_format(&formats, AVFILTER_PACKED);
> +    avfilter_set_common_packing_formats(ctx, formats);
> +
> +    return 0;
> +}
> +
> +static int config_input(AVFilterLink *inlink)
> +{
> +    if (inlink->sample_rate != 44100) {
> +        av_log(inlink->dst, AV_LOG_ERROR,
> +               "The earwax filter only works for 44.1kHz audio. Insert "
> +               "a resample filter before this\n");
> +        return AVERROR(EINVAL);
> +    }
> +    return 0;
> +}

does the code check for stereo somewhere?


> +
> +//FIXME: replace with DSPContext.scalarproduct_int16
> +static inline int16_t *scalarproduct(int16_t *in, int16_t *endin, int16_t *out)

const in, const endin


> +{
> +    int32_t sample;
> +    int16_t j;
> +
> +    while (in < endin) {
> +        sample = 0;

32 for rounding


> +        for (j = 0; j < NUMTAPS; j++)
> +            sample += in[j] * filt[j];
> +        *out = sample >> 6;
> +        out++; in++;
> +    }

i assume this matches SOX

And for the record, this can be implemented with 2 FFTs but i am not
sure it would beat a naive SIMD scalarproduct

either way, patch LGTM otherwise

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The bravest are surely those who have the clearest vision
of what is before them, glory and danger alike, and yet
notwithstanding go out to meet it. -- Thucydides
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