lavfi: port boxblur filter from libmpcodecs

With the following additions:
* support to gray format
* support to yuva420p format
* parametric luma/chroma/alpha radius
* consistency check on the radius values, avoid crashes with invalid values

Signed-off-by: Anton Khirnov <anton@khirnov.net>

Changelog

@@ -51,6 +51,7 @@ easier to use. The changes are:
 - CELT in Ogg demuxing
 - VC-1 interlaced decoding
 - lut, lutrgb, and lutyuv filters
+- boxblur filter
 
 
 version 0.7:

configure

@@ -1480,6 +1480,7 @@ udp_protocol_deps="network"
 
 # filters
 blackframe_filter_deps="gpl"
+boxblur_filter_deps="gpl"
 cropdetect_filter_deps="gpl"
 drawtext_filter_deps="libfreetype"
 frei0r_filter_deps="frei0r dlopen strtok_r"

doc/filters.texi

@@ -183,6 +183,66 @@ threshold, and defaults to 98.
 @var{threshold} is the threshold below which a pixel value is
 considered black, and defaults to 32.
 
+@section boxblur
+
+Apply boxblur algorithm to the input video.
+
+This filter accepts the parameters:
+@var{luma_power}:@var{luma_radius}:@var{chroma_radius}:@var{chroma_power}:@var{alpha_radius}:@var{alpha_power}
+
+Chroma and alpha parameters are optional, if not specified they default
+to the corresponding values set for @var{luma_radius} and
+@var{luma_power}.
+
+@var{luma_radius}, @var{chroma_radius}, and @var{alpha_radius} represent
+the radius in pixels of the box used for blurring the corresponding
+input plane. They are expressions, and can contain the following
+constants:
+@table @option
+@item w, h
+the input width and heigth in pixels
+
+@item cw, ch
+the input chroma image width and height in pixels
+
+@item hsub, vsub
+horizontal and vertical chroma subsample values. For example for the
+pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
+@end table
+
+The radius must be a non-negative number, and must not be greater than
+the value of the expression @code{min(w,h)/2} for the luma and alpha planes,
+and of @code{min(cw,ch)/2} for the chroma planes.
+
+@var{luma_power}, @var{chroma_power}, and @var{alpha_power} represent
+how many times the boxblur filter is applied to the corresponding
+plane.
+
+Some examples follow:
+
+@itemize
+
+@item
+Apply a boxblur filter with luma, chroma, and alpha radius
+set to 2:
+@example
+boxblur=2:1
+@end example
+
+@item
+Set luma radius to 2, alpha and chroma radius to 0
+@example
+boxblur=2:1:0:0:0:0
+@end example
+
+@item
+Set luma and chroma radius to a fraction of the video dimension
+@example
+boxblur=min(h\,w)/10:1:min(cw\,ch)/10:1
+@end example
+
+@end itemize
+
 @section copy
 
 Copy the input source unchanged to the output. Mainly useful for

libavfilter/Makefile

@@ -20,6 +20,7 @@ OBJS-$(CONFIG_ANULLSRC_FILTER)               += asrc_anullsrc.o
 OBJS-$(CONFIG_ANULLSINK_FILTER)              += asink_anullsink.o
 
 OBJS-$(CONFIG_BLACKFRAME_FILTER)             += vf_blackframe.o
+OBJS-$(CONFIG_BOXBLUR_FILTER)                += vf_boxblur.o
 OBJS-$(CONFIG_COPY_FILTER)                   += vf_copy.o
 OBJS-$(CONFIG_CROP_FILTER)                   += vf_crop.o
 OBJS-$(CONFIG_CROPDETECT_FILTER)             += vf_cropdetect.o

libavfilter/allfilters.c

@@ -41,6 +41,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER (ANULLSINK,   anullsink,   asink);
 
     REGISTER_FILTER (BLACKFRAME,  blackframe,  vf);
+    REGISTER_FILTER (BOXBLUR,     boxblur,     vf);
     REGISTER_FILTER (COPY,        copy,        vf);
     REGISTER_FILTER (CROP,        crop,        vf);
     REGISTER_FILTER (CROPDETECT,  cropdetect,  vf);

libavfilter/avfilter.h

@@ -29,7 +29,7 @@
 #include "libavutil/rational.h"
 
 #define LIBAVFILTER_VERSION_MAJOR  2
-#define LIBAVFILTER_VERSION_MINOR  9
+#define LIBAVFILTER_VERSION_MINOR  10
 #define LIBAVFILTER_VERSION_MICRO  0
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \

libavfilter/vf_boxblur.c

@@ -0,0 +1,350 @@
+/*
+ * Copyright (c) 2002 Michael Niedermayer <michaelni@gmx.at>
+ * Copyright (c) 2011 Stefano Sabatini
+ *
+ * This file is part of Libav.
+ *
+ * Libav is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * Libav 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with Libav; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+/**
+ * @file
+ * Apply a boxblur filter to the input video.
+ * Ported from MPlayer libmpcodecs/vf_boxblur.c.
+ */
+
+#include "libavutil/avstring.h"
+#include "libavutil/eval.h"
+#include "libavutil/pixdesc.h"
+#include "avfilter.h"
+
+static const char *var_names[] = {
+    "w",
+    "h",
+    "cw",
+    "ch",
+    "hsub",
+    "vsub",
+    NULL
+};
+
+enum var_name {
+    VAR_W,
+    VAR_H,
+    VAR_CW,
+    VAR_CH,
+    VAR_HSUB,
+    VAR_VSUB,
+    VARS_NB
+};
+
+typedef struct {
+    int radius;
+    int power;
+} FilterParam;
+
+typedef struct {
+    FilterParam luma_param;
+    FilterParam chroma_param;
+    FilterParam alpha_param;
+    char luma_radius_expr  [256];
+    char chroma_radius_expr[256];
+    char alpha_radius_expr [256];
+
+    int hsub, vsub;
+    int radius[4];
+    int power[4];
+    uint8_t *temp[2]; ///< temporary buffer used in blur_power()
+} BoxBlurContext;
+
+#define Y 0
+#define U 1
+#define V 2
+#define A 3
+
+static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
+{
+    BoxBlurContext *boxblur = ctx->priv;
+    int e;
+
+    if (!args) {
+        av_log(ctx, AV_LOG_ERROR,
+               "Filter expects 2 or 4 or 6 arguments, none provided\n");
+        return AVERROR(EINVAL);
+    }
+
+    e = sscanf(args, "%255[^:]:%d:%255[^:]:%d:%255[^:]:%d",
+               boxblur->luma_radius_expr,   &boxblur->luma_param  .power,
+               boxblur->chroma_radius_expr, &boxblur->chroma_param.power,
+               boxblur->alpha_radius_expr,  &boxblur->alpha_param .power);
+
+    if (e != 2 && e != 4 && e != 6) {
+        av_log(ctx, AV_LOG_ERROR,
+               "Filter expects 2 or 4 or 6 params, provided %d\n", e);
+        return AVERROR(EINVAL);
+    }
+
+    if (e < 4) {
+        boxblur->chroma_param.power = boxblur->luma_param.power;
+        av_strlcpy(boxblur->chroma_radius_expr, boxblur->luma_radius_expr,
+                   sizeof(boxblur->chroma_radius_expr));
+    }
+    if (e < 6) {
+        boxblur->alpha_param.power = boxblur->luma_param.power;
+        av_strlcpy(boxblur->alpha_radius_expr, boxblur->luma_radius_expr,
+                   sizeof(boxblur->alpha_radius_expr));
+    }
+
+    return 0;
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    BoxBlurContext *boxblur = ctx->priv;
+
+    av_freep(&boxblur->temp[0]);
+    av_freep(&boxblur->temp[1]);
+}
+
+static int query_formats(AVFilterContext *ctx)
+{
+    enum PixelFormat pix_fmts[] = {
+        PIX_FMT_YUV444P,  PIX_FMT_YUV422P,  PIX_FMT_YUV420P,
+        PIX_FMT_YUV411P,  PIX_FMT_YUV410P,  PIX_FMT_YUVA420P,
+        PIX_FMT_YUV440P,  PIX_FMT_GRAY8,
+        PIX_FMT_YUVJ444P, PIX_FMT_YUVJ422P, PIX_FMT_YUVJ420P,
+        PIX_FMT_YUVJ440P,
+        PIX_FMT_NONE
+    };
+
+    avfilter_set_common_formats(ctx, avfilter_make_format_list(pix_fmts));
+    return 0;
+}
+
+static int config_input(AVFilterLink *inlink)
+{
+    const AVPixFmtDescriptor *desc = &av_pix_fmt_descriptors[inlink->format];
+    AVFilterContext    *ctx = inlink->dst;
+    BoxBlurContext *boxblur = ctx->priv;
+    int w = inlink->w, h = inlink->h;
+    int cw, ch;
+    double var_values[VARS_NB], res;
+    char *expr;
+    int ret;
+
+    av_freep(&boxblur->temp[0]);
+    av_freep(&boxblur->temp[1]);
+    if (!(boxblur->temp[0] = av_malloc(FFMAX(w, h))))
+       return AVERROR(ENOMEM);
+    if (!(boxblur->temp[1] = av_malloc(FFMAX(w, h)))) {
+        av_freep(&boxblur->temp[0]);
+        return AVERROR(ENOMEM);
+    }
+
+    boxblur->hsub = desc->log2_chroma_w;
+    boxblur->vsub = desc->log2_chroma_h;
+
+    var_values[VAR_W]       = inlink->w;
+    var_values[VAR_H]       = inlink->h;
+    var_values[VAR_CW] = cw = w>>boxblur->hsub;
+    var_values[VAR_CH] = ch = h>>boxblur->vsub;
+    var_values[VAR_HSUB]    = 1<<boxblur->hsub;
+    var_values[VAR_VSUB]    = 1<<boxblur->vsub;
+
+#define EVAL_RADIUS_EXPR(comp)                                          \
+    expr = boxblur->comp##_radius_expr;                                 \
+    ret = av_expr_parse_and_eval(&res, expr, var_names, var_values,     \
+                                 NULL, NULL, NULL, NULL, NULL, 0, ctx); \
+    boxblur->comp##_param.radius = res;                                 \
+    if (ret < 0) {                                                      \
+        av_log(NULL, AV_LOG_ERROR,                                      \
+               "Error when evaluating " #comp " radius expression '%s'\n", expr); \
+        return ret;                                                     \
+    }
+    EVAL_RADIUS_EXPR(luma);
+    EVAL_RADIUS_EXPR(chroma);
+    EVAL_RADIUS_EXPR(alpha);
+
+    av_log(ctx, AV_LOG_DEBUG,
+           "luma_radius:%d luma_power:%d "
+           "chroma_radius:%d chroma_power:%d "
+           "alpha_radius:%d alpha_power:%d "
+           "w:%d chroma_w:%d h:%d chroma_h:%d\n",
+           boxblur->luma_param  .radius, boxblur->luma_param  .power,
+           boxblur->chroma_param.radius, boxblur->chroma_param.power,
+           boxblur->alpha_param .radius, boxblur->alpha_param .power,
+           w, cw, h, ch);
+
+#define CHECK_RADIUS_VAL(w_, h_, comp)                                  \
+    if (boxblur->comp##_param.radius < 0 ||                             \
+        2*boxblur->comp##_param.radius > FFMIN(w_, h_)) {               \
+        av_log(ctx, AV_LOG_ERROR,                                       \
+               "Invalid " #comp " radius value %d, must be >= 0 and <= %d\n", \
+               boxblur->comp##_param.radius, FFMIN(w_, h_)/2);          \
+        return AVERROR(EINVAL);                                         \
+    }
+    CHECK_RADIUS_VAL(w,  h,  luma);
+    CHECK_RADIUS_VAL(cw, ch, chroma);
+    CHECK_RADIUS_VAL(w,  h,  alpha);
+
+    boxblur->radius[Y] = boxblur->luma_param.radius;
+    boxblur->radius[U] = boxblur->radius[V] = boxblur->chroma_param.radius;
+    boxblur->radius[A] = boxblur->alpha_param.radius;
+
+    boxblur->power[Y] = boxblur->luma_param.power;
+    boxblur->power[U] = boxblur->power[V] = boxblur->chroma_param.power;
+    boxblur->power[A] = boxblur->alpha_param.power;
+
+    return 0;
+}
+
+static inline void blur(uint8_t *dst, int dst_step, const uint8_t *src, int src_step,
+                        int len, int radius)
+{
+    /* Naive boxblur would sum source pixels from x-radius .. x+radius
+     * for destination pixel x. That would be O(radius*width).
+     * If you now look at what source pixels represent 2 consecutive
+     * output pixels, then you see they are almost identical and only
+     * differ by 2 pixels, like:
+     * src0       111111111
+     * dst0           1
+     * src1        111111111
+     * dst1            1
+     * src0-src1  1       -1
+     * so when you know one output pixel you can find the next by just adding
+     * and subtracting 1 input pixel.
+     * The following code adopts this faster variant.
+     */
+    const int length = radius*2 + 1;
+    const int inv = ((1<<16) + length/2)/length;
+    int x, sum = 0;
+
+    for (x = 0; x < radius; x++)
+        sum += src[x*src_step]<<1;
+    sum += src[radius*src_step];
+
+    for (x = 0; x <= radius; x++) {
+        sum += src[(radius+x)*src_step] - src[(radius-x)*src_step];
+        dst[x*dst_step] = (sum*inv + (1<<15))>>16;
+    }
+
+    for (; x < len-radius; x++) {
+        sum += src[(radius+x)*src_step] - src[(x-radius-1)*src_step];
+        dst[x*dst_step] = (sum*inv + (1<<15))>>16;
+    }
+
+    for (; x < len; x++) {
+        sum += src[(2*len-radius-x-1)*src_step] - src[(x-radius-1)*src_step];
+        dst[x*dst_step] = (sum*inv + (1<<15))>>16;
+    }
+}
+
+static inline void blur_power(uint8_t *dst, int dst_step, const uint8_t *src, int src_step,
+                              int len, int radius, int power, uint8_t *temp[2])
+{
+    uint8_t *a = temp[0], *b = temp[1];
+
+    if (radius && power) {
+        blur(a, 1, src, src_step, len, radius);
+        for (; power > 2; power--) {
+            uint8_t *c;
+            blur(b, 1, a, 1, len, radius);
+            c = a; a = b; b = c;
+        }
+        if (power > 1) {
+            blur(dst, dst_step, a, 1, len, radius);
+        } else {
+            int i;
+            for (i = 0; i < len; i++)
+                dst[i*dst_step] = a[i];
+        }
+    } else {
+        int i;
+        for (i = 0; i < len; i++)
+            dst[i*dst_step] = src[i*src_step];
+    }
+}
+
+static void hblur(uint8_t *dst, int dst_linesize, const uint8_t *src, int src_linesize,
+                  int w, int h, int radius, int power, uint8_t *temp[2])
+{
+    int y;
+
+    if (radius == 0 && dst == src)
+        return;
+
+    for (y = 0; y < h; y++)
+        blur_power(dst + y*dst_linesize, 1, src + y*src_linesize, 1,
+                   w, radius, power, temp);
+}
+
+static void vblur(uint8_t *dst, int dst_linesize, const uint8_t *src, int src_linesize,
+                  int w, int h, int radius, int power, uint8_t *temp[2])
+{
+    int x;
+
+    if (radius == 0 && dst == src)
+        return;
+
+    for (x = 0; x < w; x++)
+        blur_power(dst + x, dst_linesize, src + x, src_linesize,
+                   h, radius, power, temp);
+}
+
+static void draw_slice(AVFilterLink *inlink, int y0, int h0, int slice_dir)
+{
+    AVFilterContext *ctx = inlink->dst;
+    BoxBlurContext *boxblur = ctx->priv;
+    AVFilterLink *outlink = inlink->dst->outputs[0];
+    AVFilterBufferRef *inpicref  = inlink ->cur_buf;
+    AVFilterBufferRef *outpicref = outlink->out_buf;
+    int plane;
+    int cw = inlink->w >> boxblur->hsub, ch = h0 >> boxblur->vsub;
+    int w[4] = { inlink->w, cw, cw, inlink->w };
+    int h[4] = { h0, ch, ch, h0 };
+
+    for (plane = 0; inpicref->data[plane] && plane < 4; plane++)
+        hblur(outpicref->data[plane], outpicref->linesize[plane],
+              inpicref ->data[plane], inpicref ->linesize[plane],
+              w[plane], h[plane], boxblur->radius[plane], boxblur->power[plane],
+              boxblur->temp);
+
+    for (plane = 0; inpicref->data[plane] && plane < 4; plane++)
+        vblur(outpicref->data[plane], outpicref->linesize[plane],
+              outpicref->data[plane], outpicref->linesize[plane],
+              w[plane], h[plane], boxblur->radius[plane], boxblur->power[plane],
+              boxblur->temp);
+
+    avfilter_draw_slice(outlink, y0, h0, slice_dir);
+}
+
+AVFilter avfilter_vf_boxblur = {
+    .name          = "boxblur",
+    .description   = NULL_IF_CONFIG_SMALL("Blur the input."),
+    .priv_size     = sizeof(BoxBlurContext),
+    .init          = init,
+    .uninit        = uninit,
+    .query_formats = query_formats,
+
+    .inputs    = (AVFilterPad[]) {{ .name             = "default",
+                                    .type             = AVMEDIA_TYPE_VIDEO,
+                                    .config_props     = config_input,
+                                    .draw_slice       = draw_slice,
+                                    .min_perms        = AV_PERM_READ },
+                                  { .name = NULL}},
+    .outputs   = (AVFilterPad[]) {{ .name             = "default",
+                                    .type             = AVMEDIA_TYPE_VIDEO, },
+                                  { .name = NULL}},
+};