[FFmpeg-devel] [PATCH lavfi: add showwaves filter

Nicolas George nicolas.george at normalesup.org
Mon May 21 00:07:46 CEST 2012


Le primidi 1er prairial, an CCXX, Stefano Sabatini a écrit :
> >From 1a9c356febb48a6f5b4e028728d638b199a40a51 Mon Sep 17 00:00:00 2001
> From: Stefano Sabatini <stefasab at gmail.com>
> Date: Sun, 25 Dec 2011 17:37:53 +0100
> Subject: [PATCH] lavfi: add showwaves filter
> 
> ---
>  doc/filters.texi            |   23 +++++
>  libavfilter/Makefile        |    2 +
>  libavfilter/allfilters.c    |    3 +
>  libavfilter/avf_showwaves.c |  195 +++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 223 insertions(+), 0 deletions(-)
>  create mode 100644 libavfilter/avf_showwaves.c
> 
> diff --git a/doc/filters.texi b/doc/filters.texi
> index 467fb4a..9c4575d 100644
> --- a/doc/filters.texi
> +++ b/doc/filters.texi
> @@ -3678,3 +3678,26 @@ mainly useful as a template and to be employed in analysis / debugging
>  tools.
>  
>  @c man end VIDEO SINKS
> +
> + at chapter Transmedia Filters
> + at c man begin TRANSMEDIA FILTERS
> +
> +Below is a description of the currently available transmedia filters.
> +
> + at section showwaves
> +
> +Convert input audio to a video output, representing the samples waves.
> +
> +The filter accepts the following named parameters:
> + at table @option
> + at item size, s
> +Specify the video size for the output. Default value is "320x240".
> + at end table
> +
> +The following example shows how to output the input file audio and the
> +corresponding video representation at the same time:
> + at example
> +amovie=a.mp3,asplit[out0],showwaves[out1]
> + at end example
> +
> + at c man end TRANSMEDIA FILTERS
> diff --git a/libavfilter/Makefile b/libavfilter/Makefile
> index 91f2527..7250e29 100644
> --- a/libavfilter/Makefile
> +++ b/libavfilter/Makefile
> @@ -184,6 +184,8 @@ OBJS-$(CONFIG_MP_FILTER) += libmpcodecs/vf_yuvcsp.o
>  OBJS-$(CONFIG_MP_FILTER) += libmpcodecs/vf_yvu9.o
>  OBJS-$(CONFIG_MP_FILTER) += libmpcodecs/pullup.o
>  
> +# transmedia filters
> +OBJS-$(CONFIG_SHOWWAVES_FILTER)              += avf_showwaves.o
>  
>  TESTPROGS = drawutils formats
>  
> diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
> index 29cd3e3..275744b 100644
> --- a/libavfilter/allfilters.c
> +++ b/libavfilter/allfilters.c
> @@ -123,6 +123,9 @@ void avfilter_register_all(void)
>      REGISTER_FILTER (BUFFERSINK,  buffersink,  vsink);
>      REGISTER_FILTER (NULLSINK,    nullsink,    vsink);
>  
> +    /* transmedia filters */
> +    REGISTER_FILTER (SHOWWAVES,   showwaves,   avf);
> +
>      /* those filters are part of public or internal API => registered
>       * unconditionally */
>      {
> diff --git a/libavfilter/avf_showwaves.c b/libavfilter/avf_showwaves.c
> new file mode 100644
> index 0000000..fdaa718
> --- /dev/null
> +++ b/libavfilter/avf_showwaves.c
> @@ -0,0 +1,195 @@
> +/*
> + * Copyright (c) 2011 Stefano Sabatini
> + *
> + * 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
> + * audio to video transmedia filter
> + */
> +
> +#include "libavutil/audioconvert.h"
> +#include "libavutil/opt.h"
> +#include "libavutil/parseutils.h"
> +#include "avfilter.h"
> +#include "formats.h"
> +
> +typedef struct {
> +    const AVClass *class;
> +    int w, h;
> +    char *size_str;
> +    int buf_idx;
> +    AVFilterBufferRef *outpicref;
> +} ShowWavesContext;
> +
> +#define OFFSET(x) offsetof(ShowWavesContext, x)
> +
> +static const AVOption showwaves_options[] = {
> +    { "size", "set video size",   OFFSET(size_str), AV_OPT_TYPE_STRING, {.str = "320x240"}, 0, 0 },
> +    { "s",    "set video size",   OFFSET(size_str), AV_OPT_TYPE_STRING, {.str = "320x240"}, 0, 0 },
> +    { NULL },
> +};
> +
> +static const char *showwaves_get_name(void *ctx)
> +{
> +    return "showwaves";
> +}
> +
> +static const AVClass showwaves_class = {
> +    "ShowWavesContext",
> +    showwaves_get_name,
> +    showwaves_options
> +};
> +
> +static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
> +{
> +    ShowWavesContext *showwaves = ctx->priv;
> +    int err;
> +
> +    showwaves->class = &showwaves_class;
> +    av_opt_set_defaults(showwaves);
> +
> +    if ((err = (av_set_options_string(showwaves, args, "=", ":"))) < 0) {
> +        av_log(ctx, AV_LOG_ERROR, "Error parsing options string: '%s'\n", args);
> +        return err;
> +    }
> +
> +    if (av_parse_video_size(&showwaves->w, &showwaves->h, showwaves->size_str) < 0) {
> +        av_log(ctx, AV_LOG_ERROR, "Invalid frame size: %s\n", showwaves->size_str);
> +        return AVERROR(EINVAL);
> +    }

Can be simplified now.

> +
> +    return 0;
> +}
> +
> +static int query_formats(AVFilterContext *ctx)
> +{
> +    AVFilterFormats *formats = NULL;
> +    AVFilterChannelLayouts *layouts = NULL;
> +    AVFilterLink *inlink = ctx->inputs[0];
> +    AVFilterLink *outlink = ctx->outputs[0];
> +    static const enum AVSampleFormat sample_fmts[] = { AV_SAMPLE_FMT_DBL, -1 };

Why double? A reasonable video size will never go beyond the precision of
S16.

> +    static const enum PixelFormat pix_fmts[] = { PIX_FMT_GRAY8, -1 };
> +
> +    /* set input audio formats */
> +    formats = avfilter_make_format_list(sample_fmts);
> +    if (!formats)
> +        return AVERROR(ENOMEM);
> +    avfilter_formats_ref(formats, &inlink->out_formats);
> +
> +    layouts = ff_all_channel_layouts();
> +    if (!layouts)
> +        return AVERROR(ENOMEM);
> +    ff_channel_layouts_ref(layouts, &inlink->out_channel_layouts);
> +
> +    formats = ff_all_samplerates();
> +    if (!formats)
> +        return AVERROR(ENOMEM);
> +    avfilter_formats_ref(formats, &inlink->out_samplerates);
> +
> +    /* set output video format */
> +    formats = avfilter_make_format_list(pix_fmts);
> +    if (!formats)
> +        return AVERROR(ENOMEM);
> +    avfilter_formats_ref(formats, &outlink->in_formats);
> +
> +    return 0;
> +}
> +
> +static int config_output(AVFilterLink *outlink)
> +{
> +    AVFilterContext *ctx = outlink->src;
> +    ShowWavesContext *showwaves = ctx->priv;
> +
> +    outlink->w = showwaves->w;
> +    outlink->h = showwaves->h;
> +
> +    av_log(ctx, AV_LOG_INFO, "s:%dx%d\n", showwaves->w, showwaves->h);
> +    return 0;
> +}
> +
> +static void filter_samples(AVFilterLink *inlink, AVFilterBufferRef *insamples)
> +{
> +    AVFilterContext *ctx = inlink->dst;
> +    AVFilterLink *outlink = ctx->outputs[0];
> +    ShowWavesContext *showwaves = ctx->priv;
> +    const int nb_samples = insamples->audio->nb_samples;
> +    AVFilterBufferRef *outpicref = showwaves->outpicref;
> +    int linesize = outpicref ? outpicref->linesize[0] : 0;
> +    double *p = (double *)insamples->data[0];
> +    int nb_channels = av_get_channel_layout_nb_channels(insamples->audio->channel_layout);
> +    int i, j, h;
> +
> +    /* draw data in the buffer */
> +    for (i = 0; i < nb_samples; i++) {
> +        if (showwaves->buf_idx == 0) {
> +            showwaves->outpicref = outpicref =
> +                avfilter_get_video_buffer(outlink, AV_PERM_WRITE|AV_PERM_ALIGN,
> +                                          outlink->w, outlink->h);
> +            outpicref->video->w = outlink->w;
> +            outpicref->video->h = outlink->h;
> +            outpicref->pts = insamples->pts + i * inlink->time_base.num / (inlink->time_base.den * inlink->sample_rate);

av_rescale?

> +            outlink->out_buf = outpicref;
> +            linesize = outpicref->linesize[0];
> +            memset(outpicref->data[0], 0, showwaves->h*linesize);
> +        }
> +        for (j = 0; j < nb_channels; j++) {
> +            h = showwaves->h/2 - (*p++ * showwaves->h/2);

av_clip(av_rescale())?

> +            if (h < outlink->h)
> +                *(outpicref->data[0] + showwaves->buf_idx + h * linesize) = 255;
> +        }
> +        showwaves->buf_idx++;

With the default frame size, at 44100Hz it outputs ~138 frames per second.
That would be barely readable. Dividing buf_idx by some constant would solve
the problem at almost no cost.

> +
> +        if (showwaves->buf_idx == showwaves->w-1) {
> +            avfilter_start_frame(outlink, outpicref);
> +            avfilter_draw_slice(outlink, 0, outlink->h, 1);
> +            avfilter_end_frame(outlink);
> +            showwaves->outpicref = NULL;
> +            showwaves->buf_idx = 0;
> +        }
> +    }

No EOF flushing, it seems. Fine by me.

OTOH, it looks like the last buffer is leaked.

> +
> +    avfilter_unref_buffer(insamples);
> +}
> +
> +AVFilter avfilter_avf_showwaves = {
> +    .name           = "showwaves",
> +    .description    = NULL_IF_CONFIG_SMALL("Convert input audio to a video output."),
> +    .init           = init,
> +    .query_formats  = query_formats,
> +    .priv_size      = sizeof(ShowWavesContext),
> +
> +    .inputs  = (const AVFilterPad[]) {
> +        {
> +            .name           = "default",
> +            .type           = AVMEDIA_TYPE_AUDIO,
> +            .filter_samples = filter_samples,
> +            .min_perms      = AV_PERM_READ,
> +        },
> +        { .name = NULL }
> +    },
> +
> +    .outputs = (const AVFilterPad[]) {
> +        {
> +            .name           = "default",
> +            .config_props   = config_output,
> +            .type           = AVMEDIA_TYPE_VIDEO,
> +        },
> +        { .name = NULL }
> +    },
> +};

Regards,

-- 
  Nicolas George
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