lavfi: add showspectrum filter.

Changelog

@@ -23,7 +23,7 @@ version next:
 - RTMPTS protocol support
 - RTMPE protocol support
 - RTMPTE protocol support
-- showwaves filter
+- showwaves and showspectrum filter
 - LucasArts SMUSH playback support
 - SAMI, RealText and SubViewer demuxers and decoders
 - Heart Of Darkness PAF playback support

configure

@@ -1849,6 +1849,7 @@ pan_filter_deps="swresample"
 removelogo_filter_deps="avcodec avformat swscale"
 scale_filter_deps="swscale"
 select_filter_deps="avcodec"
+showspectrum_filter_deps="avcodec"
 super2xsai_filter_deps="gpl"
 tinterlace_filter_deps="gpl"
 yadif_filter_deps="gpl"

doc/filters.texi

@@ -4252,6 +4252,20 @@ do not have exactly the same duration in the first file.
 
 @end itemize
 
+@section showspectrum
+
+Convert input audio to a video output, representing the audio frequency
+spectrum.
+
+The filter accepts the following named parameters:
+@table @option
+@item size, s
+Specify the video size for the output. Default value is @code{640x480}.
+@end table
+
+The usage is very similar to the showwaves filter; see the examples in that
+section.
+
 @section showwaves
 
 Convert input audio to a video output, representing the samples waves.

libavfilter/Makefile

@@ -202,6 +202,7 @@ OBJS-$(CONFIG_MP_FILTER) += libmpcodecs/pullup.o
 
 # multimedia filters
 OBJS-$(CONFIG_CONCAT_FILTER)                 += avf_concat.o
+OBJS-$(CONFIG_SHOWSPECTRUM_FILTER)           += avf_showspectrum.o
 OBJS-$(CONFIG_SHOWWAVES_FILTER)              += avf_showwaves.o
 
 # multimedia sources

libavfilter/allfilters.c

@@ -143,6 +143,7 @@ void avfilter_register_all(void)
 
     /* multimedia filters */
     REGISTER_FILTER (CONCAT,      concat,      avf);
+    REGISTER_FILTER (SHOWSPECTRUM,showspectrum,avf);
     REGISTER_FILTER (SHOWWAVES,   showwaves,   avf);
 
     /* multimedia sources */

libavfilter/avf_showspectrum.c

@@ -0,0 +1,314 @@
+/*
+ * Copyright (c) 2012 Clément Bœsch
+ *
+ * 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 rdft showmode
+ * (by Michael Niedermayer) and lavfi/avf_showwaves (by Stefano Sabatini).
+ */
+
+#include <math.h>
+
+#include "libavcodec/avfft.h"
+#include "libavutil/audioconvert.h"
+#include "libavutil/opt.h"
+#include "avfilter.h"
+#include "internal.h"
+
+typedef struct {
+    const AVClass *class;
+    int w, h;
+    AVFilterBufferRef *outpicref;
+    int req_fullfilled;
+    int xpos;                   ///< x position (current column)
+    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 in current rdft_buffer
+    int consumed;               ///< number of samples (per channel) consumed from the input frame
+    float *window_func_lut;     ///< Window function LUT
+} ShowSpectrumContext;
+
+#define OFFSET(x) offsetof(ShowSpectrumContext, x)
+
+static const AVOption showspectrum_options[] = {
+    { "size", "set video size", OFFSET(w), AV_OPT_TYPE_IMAGE_SIZE, {.str = "640x480"}, 0, 0 },
+    { "s",    "set video size", OFFSET(w), AV_OPT_TYPE_IMAGE_SIZE, {.str = "640x480"}, 0, 0 },
+    { NULL },
+};
+
+AVFILTER_DEFINE_CLASS(showspectrum);
+
+static av_cold int init(AVFilterContext *ctx, const char *args)
+{
+    ShowSpectrumContext *showspectrum = ctx->priv;
+    int err;
+
+    showspectrum->class = &showspectrum_class;
+    av_opt_set_defaults(showspectrum);
+
+    if ((err = av_set_options_string(showspectrum, args, "=", ":")) < 0)
+        return err;
+
+    return 0;
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    ShowSpectrumContext *showspectrum = ctx->priv;
+
+    av_rdft_end(showspectrum->rdft);
+    av_freep(&showspectrum->rdft_data);
+    av_freep(&showspectrum->window_func_lut);
+    avfilter_unref_bufferp(&showspectrum->outpicref);
+}
+
+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_RGB24, -1 };
+
+    /* set input audio formats */
+    formats = ff_make_format_list(sample_fmts);
+    if (!formats)
+        return AVERROR(ENOMEM);
+    ff_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);
+    ff_formats_ref(formats, &inlink->out_samplerates);
+
+    /* set output video format */
+    formats = ff_make_format_list(pix_fmts);
+    if (!formats)
+        return AVERROR(ENOMEM);
+    ff_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;
+
+    /* (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 */
+        showspectrum->rdft_data =
+            av_realloc_f(showspectrum->rdft_data, 2 * win_size,
+                         sizeof(*showspectrum->rdft_data));
+        if (!showspectrum->rdft_data)
+            return AVERROR(ENOMEM);
+        showspectrum->filled = 0;
+
+        /* pre-calc windowing function (hann here) */
+        showspectrum->window_func_lut =
+            av_realloc_f(showspectrum->window_func_lut, win_size,
+                         sizeof(*showspectrum->window_func_lut));
+        if (!showspectrum->window_func_lut)
+            return AVERROR(ENOMEM);
+        for (i = 0; i < win_size; i++)
+            showspectrum->window_func_lut[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 =
+            ff_get_video_buffer(outlink, AV_PERM_WRITE|AV_PERM_PRESERVE|AV_PERM_REUSE2,
+                                outlink->w, outlink->h);
+        if (!outpicref)
+            return AVERROR(ENOMEM);
+        outlink->sample_aspect_ratio = (AVRational){1,1};
+        memset(outpicref->data[0], 0, outlink->h * outpicref->linesize[0]);
+    }
+
+    if (showspectrum->xpos >= outlink->w)
+        showspectrum->xpos = 0;
+
+    av_log(ctx, AV_LOG_VERBOSE, "s:%dx%d RDFT window size:%d\n",
+           showspectrum->w, showspectrum->h, win_size);
+    return 0;
+}
+
+inline static void push_frame(AVFilterLink *outlink)
+{
+    ShowSpectrumContext *showspectrum = outlink->src->priv;
+
+    showspectrum->xpos++;
+    if (showspectrum->xpos >= outlink->w)
+        showspectrum->xpos = 0;
+    showspectrum->filled = 0;
+    showspectrum->req_fullfilled = 1;
+
+    ff_start_frame(outlink, avfilter_ref_buffer(showspectrum->outpicref, ~AV_PERM_WRITE));
+    ff_draw_slice(outlink, 0, outlink->h, 1);
+    ff_end_frame(outlink);
+}
+
+static int request_frame(AVFilterLink *outlink)
+{
+    ShowSpectrumContext *showspectrum = outlink->src->priv;
+    AVFilterLink *inlink = outlink->src->inputs[0];
+    int ret;
+
+    showspectrum->req_fullfilled = 0;
+    do {
+        ret = ff_request_frame(inlink);
+    } while (!showspectrum->req_fullfilled && ret >= 0);
+
+    if (ret == AVERROR_EOF && showspectrum->outpicref)
+        push_frame(outlink);
+    return ret;
+}
+
+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);
+
+    /* 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];
+
+        p += showspectrum->consumed;
+        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->window_func_lut[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++) {
+            // FIXME: bin[0] contains first and last bins
+            const int pos = showspectrum->xpos * 3 + (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;
+            outpicref->data[0][pos+1] = b;
+            outpicref->data[0][pos+2] = (a + b) / 2;
+        }
+        outpicref->pts = insamples->pts +
+            av_rescale_q(showspectrum->consumed,
+                         (AVRational){ 1, inlink->sample_rate },
+                         outlink->time_base);
+        push_frame(outlink);
+    }
+
+    return add_samples;
+}
+
+static int filter_samples(AVFilterLink *inlink, AVFilterBufferRef *insamples)
+{
+    AVFilterContext *ctx = inlink->dst;
+    ShowSpectrumContext *showspectrum = ctx->priv;
+    int left_samples = insamples->audio->nb_samples;
+
+    showspectrum->consumed = 0;
+    while (left_samples) {
+        const int added_samples = plot_spectrum_column(inlink, insamples, left_samples);
+        showspectrum->consumed += added_samples;
+        left_samples -= added_samples;
+    }
+
+    avfilter_unref_buffer(insamples);
+    return 0;
+}
+
+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",
+            .type           = AVMEDIA_TYPE_VIDEO,
+            .config_props   = config_output,
+            .request_frame  = request_frame,
+        },
+        { .name = NULL }
+    },
+};

libavfilter/version.h

@@ -29,8 +29,8 @@
 #include "libavutil/avutil.h"
 
 #define LIBAVFILTER_VERSION_MAJOR  3
-#define LIBAVFILTER_VERSION_MINOR  11
-#define LIBAVFILTER_VERSION_MICRO 101
+#define LIBAVFILTER_VERSION_MINOR  12
+#define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
                                                LIBAVFILTER_VERSION_MINOR, \