[FFmpeg-devel] [PATCH] lavfi/WIP: add showspectrum filter.

Stefano Sabatini stefasab at gmail.com
Mon Jul 30 11:02:26 CEST 2012


On date Thursday 2012-05-24 08:15:34 +0200, Clément Bœsch encoded:
> ---
> Here is a WIP showspectrum patch to be applied on top of Stefano's showwaves
> experimental filter¹.
> 
> I try to keep the two filters similar, so the filter is ATM "in sync" with
> Stefano's WIP, and I'll re-sync when showwaves is upstream.
> 
> The main left thing to do is the colors (shouldn't be hard).
> 
> Another other thing I'm wondering about is how am I really supposed to
> normalize the magnitudes (done ATM with the w = 1/sqrt(nb_freq)); it works now
> since I'm just taking ffplay code, but I'd like to support double/float at some
> point, and this formula doesn't work well: I can't really tell what's the range
> of possible values for the magnitude when samples are in [0,1]. Also, they
> don't seem to be linearly distributed (I can have a high maximum, but most
> values are pretty low).
> 
> Last important thing is that I need to fix is the heavy memleak...
> 
> [1]: or you can just remote add git://github.com/ubitux/FFmpeg.git and checkout
>      the appropriate branch
> ---
>  libavfilter/Makefile           |    1 +
>  libavfilter/allfilters.c       |    1 +
>  libavfilter/avf_showspectrum.c |  297 ++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 299 insertions(+)
>  create mode 100644 libavfilter/avf_showspectrum.c
> 
> diff --git a/libavfilter/Makefile b/libavfilter/Makefile
> index 7c2c525..ae48ca6 100644
> --- a/libavfilter/Makefile
> +++ b/libavfilter/Makefile
> @@ -187,6 +187,7 @@ OBJS-$(CONFIG_MP_FILTER) += libmpcodecs/vf_yvu9.o
>  OBJS-$(CONFIG_MP_FILTER) += libmpcodecs/pullup.o
>  
>  # transmedia filters
> +OBJS-$(CONFIG_SHOWSPECTRUM_FILTER)           += avf_showspectrum.o
>  OBJS-$(CONFIG_SHOWWAVES_FILTER)              += avf_showwaves.o
>  
>  TESTPROGS = drawutils formats
> diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
> index c48c2d7..21dd045 100644
> --- a/libavfilter/allfilters.c
> +++ b/libavfilter/allfilters.c
> @@ -125,6 +125,7 @@ void avfilter_register_all(void)
>      REGISTER_FILTER (NULLSINK,    nullsink,    vsink);
>  
>      /* transmedia filters */
> +    REGISTER_FILTER (SHOWSPECTRUM,showspectrum,avf);
>      REGISTER_FILTER (SHOWWAVES,   showwaves,   avf);
>  
>      /* those filters are part of public or internal API => registered
> diff --git a/libavfilter/avf_showspectrum.c b/libavfilter/avf_showspectrum.c
> new file mode 100644
> index 0000000..6e0977d
> --- /dev/null
> +++ b/libavfilter/avf_showspectrum.c
> @@ -0,0 +1,297 @@
> +/*
> + * Copyright (c) 2012 Clément Bœsch
> + * 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 spectrum (video) transmedia filter, based on ffplay showmode and
> + * lavfi/avf_showaudio

showwaves

> + */
> +
> +#include <math.h>
> +
> +#include "libavcodec/avfft.h"
> +#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 xpos;
> +    AVFilterBufferRef *outpicref;
> +
> +    RDFTContext *rdft;          ///< Real Discrete Fourier Transform context
> +    int rdft_bits;              ///< number of bits (RDFT window size = 1<<rdft_bits)
> +    FFTSample *rdft_data;       ///< bins holder for each (displayed) channels
> +    int filled;                 ///< number of samples (per channel) filled
> +    float *windowing;           ///< Window function LUT
> +} ShowSpectrumContext;
> +
> +#define OFFSET(x) offsetof(ShowSpectrumContext, x)
> +

> +static const AVOption showspectrum_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 },

AV_OPT_IMAGE_SIZE


> +    { NULL },
> +};
> +
> +static const char *showspectrum_get_name(void *ctx)
> +{
> +    return "showspectrum";
> +}
> +
> +static const AVClass showspectrum_class = {
> +    "ShowSpectrumContext",
> +    showspectrum_get_name,
> +    showspectrum_options
> +};

AVFILTER_DEFINE_CLASS

> +
> +static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
> +{
> +    ShowSpectrumContext *showspectrum = ctx->priv;
> +    int err;
> +
> +    showspectrum->class = &showspectrum_class;
> +    av_opt_set_defaults(showspectrum);
> +
> +    if ((err = (av_set_options_string(showspectrum, args, "=", ":"))) < 0) {
> +        av_log(ctx, AV_LOG_ERROR, "Error parsing options string: '%s'\n", args);
> +        return err;
> +    }
> +
> +    if (av_parse_video_size(&showspectrum->w, &showspectrum->h, showspectrum->size_str) < 0) {
> +        av_log(ctx, AV_LOG_ERROR, "Invalid frame size: %s\n", showspectrum->size_str);
> +        return AVERROR(EINVAL);
> +    }
> +
> +    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_S16P, -1 };
> +    static const enum PixelFormat pix_fmts[] = { PIX_FMT_GRAY8, -1 }; // TODO: color
> +

> +    /* 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);

Note: we may find some clever way to wrap this in a shared function.

> +
> +    /* 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;
> +    ShowSpectrumContext *showspectrum = ctx->priv;
> +    int i, rdft_bits, win_size;
> +
> +    outlink->w = showspectrum->w;
> +    outlink->h = showspectrum->h;
> +
> +    /* RDFT window size (precision) according to the requested output frame height */
> +    for (rdft_bits = 1; 1<<rdft_bits < 2*outlink->h; rdft_bits++);
> +    win_size = 1 << rdft_bits;

> +    av_log(ctx, AV_LOG_INFO, "s:%dx%d RDFT N:%d\n", showspectrum->w, showspectrum->h, win_size);

INFO -> VERBOSE
also N -> win_size

> +
> +    /* (re-)configuration if the video output changed (or first init) */
> +    if (rdft_bits != showspectrum->rdft_bits) {
> +        AVFilterBufferRef *outpicref;
> +
> +        av_rdft_end(showspectrum->rdft);
> +        showspectrum->rdft = av_rdft_init(rdft_bits, DFT_R2C);
> +        showspectrum->rdft_bits = rdft_bits;
> +
> +        /* RDFT buffers: x2 for each (display) channel buffer */
> +        av_free(showspectrum->rdft_data);
> +        showspectrum->rdft_data = av_malloc(2 * win_size * sizeof(*showspectrum->rdft_data));
> +        if (!showspectrum->rdft_data)
> +            return AVERROR(ENOMEM);
> +        showspectrum->filled = 0;
> +
> +        /* pre-calc windowing function (hann here) */
> +        av_free(showspectrum->windowing);
> +        showspectrum->windowing = av_malloc(win_size * sizeof(*showspectrum->windowing));
> +        if (!showspectrum->windowing)
> +            return AVERROR(ENOMEM);
> +        for (i = 0; i < win_size; i++)
> +            showspectrum->windowing[i] = .5f * (1 - cos(2*M_PI*i / (win_size-1)));
> +
> +        /* prepare the initial picref buffer (black frame) */
> +        avfilter_unref_bufferp(&showspectrum->outpicref);

> +        showspectrum->outpicref = outpicref =
> +            avfilter_get_video_buffer(outlink, AV_PERM_WRITE|AV_PERM_ALIGN,

AV_PERM_WRITE|AV_PERM_ALIGN|AV_PERM_PRESERVE

(see below)

Is ALIGN really required?

> +                                      outlink->w, outlink->h);



> +        outpicref->video->w = outlink->w;
> +        outpicref->video->h = outlink->h;
> +        memset(outpicref->data[0], 0, outlink->h * outpicref->linesize[0]);

please check that the buffer is not already zeroed, drop the memset in
that case, REUSE* flags are useful for the frame allocator, so you
should use REUSE2 in this case.

> +        showspectrum->xpos = 0;
> +    }
> +
> +    return 0;
> +}
> +
> +static int plot_spectrum_column(AVFilterLink *inlink, AVFilterBufferRef *insamples, int nb_samples)
> +{
> +    AVFilterContext *ctx = inlink->dst;
> +    AVFilterLink *outlink = ctx->outputs[0];
> +    ShowSpectrumContext *showspectrum = ctx->priv;
> +    AVFilterBufferRef *outpicref = showspectrum->outpicref;
> +    const int nb_channels = av_get_channel_layout_nb_channels(insamples->audio->channel_layout);
> +
> +    /* nb_freq contains the power of two superior or equal to the output image
> +     * height (or half the RDFT window size) */
> +    const int nb_freq = 1 << (showspectrum->rdft_bits - 1);
> +    const int win_size = nb_freq << 1;
> +
> +    int ch, n, y;
> +    FFTSample *data[2];
> +    const int nb_display_channels = FFMIN(nb_channels, 2);
> +    const int start = showspectrum->filled;
> +    const int add_samples = FFMIN(win_size - start, nb_samples);
> +
> +    //av_log(0,0,"rdft_data: %d/%d <=== input: %d (-> insert %d samples)\n",
> +    //       win_size, start, nb_samples, add_samples);
> +
> +    /* fill RDFT input with the number of samples available */
> +    for (ch = 0; ch < nb_display_channels; ch++) {
> +        const int16_t *p = (int16_t *)insamples->extended_data[ch];
> +
> +        data[ch] = showspectrum->rdft_data + win_size * ch; // select channel buffer
> +        for (n = 0; n < add_samples; n++)
> +            data[ch][start + n] = p[n] * showspectrum->windowing[start + n];
> +    }
> +    showspectrum->filled += add_samples;
> +
> +    /* complete RDFT window size? */
> +    if (showspectrum->filled == win_size) {
> +
> +        /* run RDFT on each samples set */
> +        for (ch = 0; ch < nb_display_channels; ch++)
> +            av_rdft_calc(showspectrum->rdft, data[ch]);
> +
> +        /* fill a new spectrum column */
> +#define RE(ch) data[ch][2*y + 0]
> +#define IM(ch) data[ch][2*y + 1]
> +#define MAGNITUDE(re, im) sqrt((re)*(re) + (im)*(im))
> +        for (y = 0; y < outlink->h; y++) {
> +            static float max;
> +            // FIXME: bin[0] contains first and last bins
> +            const int pos = showspectrum->xpos + (outlink->h - y - 1) * outpicref->linesize[0];
> +            const double w = 1. / sqrt(nb_freq);
> +            int a =                           sqrt(w * MAGNITUDE(RE(0), IM(0)));
> +            int b = nb_display_channels > 1 ? sqrt(w * MAGNITUDE(RE(1), IM(1))) : a;
> +
> +            a = FFMIN(a, 255);
> +            b = FFMIN(b, 255);
> +            outpicref->data[0][pos] = (a + b) / 2;
> +        }
> +        showspectrum->xpos++;
> +        if (showspectrum->xpos == outlink->w)
> +            showspectrum->xpos = 0;
> +
> +        /* send the frame (RO because it is re-used in this filter each time)
> +         * to the next filter */
> +        outpicref->pts = insamples->pts +
> +            showspectrum->filled * inlink->time_base.num / (inlink->time_base.den * inlink->sample_rate);
> +        avfilter_start_frame(outlink, avfilter_ref_buffer(outpicref, ~0));

You have a buffer WRITE+ALIGN+REUSE2+READ (READ flag is automatically
added by the filtering system). You need to add the PRESERVE flag and
remove the WRITE flag, so the better way is to do
avfilter_ref_buffer(outpicref, ~AV_PERM_READ), and request the frame
with the flag PRESERVE in config.

> +        avfilter_draw_slice(outlink, 0, outlink->h, 1);
> +        avfilter_end_frame(outlink);
> +        //FIXME: seems to leak heavily (+slow?)
> +
> +        showspectrum->filled = 0;
> +    }
> +
> +    return nb_samples - add_samples;
> +}
> +
> +static void filter_samples(AVFilterLink *inlink, AVFilterBufferRef *insamples)
> +{
> +    int left_samples = insamples->audio->nb_samples;
> +
> +    while (left_samples) {
> +        //av_log(0,0,"left_samples=%d\n", left_samples);
> +        left_samples = plot_spectrum_column(inlink, insamples, left_samples);

Would make more sense to return the number of consumed samples and do:
left_samples -= plot_spectrum_column...

[...]

Missing docs.
-- 
FFmpeg = Foolish Fostering Multimedia Pitiful Embarassing Governor


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