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

Clément Bœsch ubitux at gmail.com
Thu May 24 08:15:34 CEST 2012


---
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
+ */
+
+#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 },
+    { NULL },
+};
+
+static const char *showspectrum_get_name(void *ctx)
+{
+    return "showspectrum";
+}
+
+static const AVClass showspectrum_class = {
+    "ShowSpectrumContext",
+    showspectrum_get_name,
+    showspectrum_options
+};
+
+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);
+
+    /* 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);
+
+    /* (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,
+                                      outlink->w, outlink->h);
+        outpicref->video->w = outlink->w;
+        outpicref->video->h = outlink->h;
+        memset(outpicref->data[0], 0, outlink->h * outpicref->linesize[0]);
+        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));
+        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);
+    }
+    avfilter_unref_buffer(insamples);
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    ShowSpectrumContext *showspectrum = ctx->priv;
+
+    av_rdft_end(showspectrum->rdft);
+    av_freep(&showspectrum->rdft_data);
+    avfilter_unref_bufferp(&showspectrum->outpicref);
+}
+
+AVFilter avfilter_avf_showspectrum = {
+    .name           = "showspectrum",
+    .description    = NULL_IF_CONFIG_SMALL("Convert input audio to a spectrum video output."),
+    .init           = init,
+    .uninit         = uninit,
+    .query_formats  = query_formats,
+    .priv_size      = sizeof(ShowSpectrumContext),
+
+    .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 }
+    },
+};
-- 
1.7.10.2



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