lavfi: port decimate libmpcodecs filter

This filter is based on the MPlayer decimate filter by Rich Felker.

Changelog

@@ -58,6 +58,7 @@ version next:
   instead of AV_CODEC_ID_TEXT
 - smartblur filter ported from MPlayer
 - CPiA decoder
+- decimate filter ported from MPlayer
 
 
 version 0.11:

configure

@@ -1889,6 +1889,7 @@ blackframe_filter_deps="gpl"
 boxblur_filter_deps="gpl"
 colormatrix_filter_deps="gpl"
 cropdetect_filter_deps="gpl"
+decimate_filter_deps="gpl"
 delogo_filter_deps="gpl"
 deshake_filter_deps="avcodec"
 drawtext_filter_deps="libfreetype"

doc/filters.texi

@@ -1539,6 +1539,43 @@ indicates never reset and return the largest area encountered during
 playback.
 @end table
 
+@section decimate
+
+This filter drops frames that do not differ greatly from the previous
+frame in order to reduce framerate.  The main use of this filter is
+for very-low-bitrate encoding (e.g. streaming over dialup modem), but
+it could in theory be used for fixing movies that were
+inverse-telecined incorrectly.
+
+It accepts the following parameters:
+@var{max}:@var{hi}:@var{lo}:@var{frac}.
+
+@table @option
+
+@item max
+Set the maximum number of consecutive frames which can be dropped (if
+positive), or the minimum interval between dropped frames (if
+negative). If the value is 0, the frame is dropped unregarding the
+number of previous sequentially dropped frames.
+
+Default value is 0.
+
+@item hi, lo, frac
+Set the dropping threshold values.
+
+Values for @var{hi} and @var{lo} are for 8x8 pixel blocks and
+represent actual pixel value differences, so a threshold of 64
+corresponds to 1 unit of difference for each pixel, or the same spread
+out differently over the block.
+
+A frame is a candidate for dropping if no 8x8 blocks differ by more
+than a threshold of @var{hi}, and if no more than @var{frac} blocks (1
+meaning the whole image) differ by more than a threshold of @var{lo}.
+
+Default value for @var{hi} is 64*12, default value for @var{lo} is
+64*5, and default value for @var{frac} is 0.33.
+@end table
+
 @section delogo
 
 Suppress a TV station logo by a simple interpolation of the surrounding

libavfilter/Makefile

@@ -10,6 +10,7 @@ FFLIBS-$(CONFIG_ACONVERT_FILTER)             += swresample
 FFLIBS-$(CONFIG_AMOVIE_FILTER)               += avformat avcodec
 FFLIBS-$(CONFIG_ARESAMPLE_FILTER)            += swresample
 FFLIBS-$(CONFIG_ATEMPO_FILTER)               += avcodec
+FFLIBS-$(CONFIG_DECIMATE_FILTER)             += avcodec
 FFLIBS-$(CONFIG_MOVIE_FILTER)                += avformat avcodec
 FFLIBS-$(CONFIG_PAN_FILTER)                  += swresample
 FFLIBS-$(CONFIG_REMOVELOGO_FILTER)           += avformat avcodec
@@ -88,6 +89,7 @@ OBJS-$(CONFIG_COLORMATRIX_FILTER)            += vf_colormatrix.o
 OBJS-$(CONFIG_COPY_FILTER)                   += vf_copy.o
 OBJS-$(CONFIG_CROP_FILTER)                   += vf_crop.o
 OBJS-$(CONFIG_CROPDETECT_FILTER)             += vf_cropdetect.o
+OBJS-$(CONFIG_DECIMATE_FILTER)               += vf_decimate.o
 OBJS-$(CONFIG_DELOGO_FILTER)                 += vf_delogo.o
 OBJS-$(CONFIG_DESHAKE_FILTER)                += vf_deshake.o
 OBJS-$(CONFIG_DRAWBOX_FILTER)                += vf_drawbox.o

libavfilter/allfilters.c

@@ -78,6 +78,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER (COPY,        copy,        vf);
     REGISTER_FILTER (CROP,        crop,        vf);
     REGISTER_FILTER (CROPDETECT,  cropdetect,  vf);
+    REGISTER_FILTER (DECIMATE,    decimate,    vf);
     REGISTER_FILTER (DELOGO,      delogo,      vf);
     REGISTER_FILTER (DESHAKE,     deshake,     vf);
     REGISTER_FILTER (DRAWBOX,     drawbox,     vf);

libavfilter/version.h

@@ -29,8 +29,8 @@
 #include "libavutil/avutil.h"
 
 #define LIBAVFILTER_VERSION_MAJOR  3
-#define LIBAVFILTER_VERSION_MINOR  14
+#define LIBAVFILTER_VERSION_MINOR  15
-#define LIBAVFILTER_VERSION_MICRO 101
+#define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
                                                LIBAVFILTER_VERSION_MINOR, \

libavfilter/vf_decimate.c

@@ -0,0 +1,268 @@
+/*
+ * Copyright (c) 2003 Rich Felker
+ * Copyright (c) 2012 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 General Public License as published by
+ * the Free Software Foundation; either version 2 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU 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 decimate filter, ported from libmpcodecs/vf_decimate.c by
+ * Rich Felker.
+ */
+
+#include "libavutil/pixdesc.h"
+#include "libavutil/timestamp.h"
+#include "libavcodec/dsputil.h"
+#include "avfilter.h"
+#include "internal.h"
+#include "formats.h"
+#include "video.h"
+
+typedef struct {
+    int lo, hi;                    ///< lower and higher threshold number of differences
+                                   ///< values for 8x8 blocks
+
+    float frac;                    ///< threshold of changed pixels over the total fraction
+
+    int max_drop_count;            ///< if positive: maximum number of sequential frames to drop
+                                   ///< if negative: minimum number of frames between two drops
+
+    int drop_count;                ///< if positive: number of frames sequentially dropped
+                                   ///< if negative: number of sequential frames which were not dropped
+
+    int hsub, vsub;                ///< chroma subsampling values
+    AVFilterBufferRef *ref;        ///< reference picture
+    DSPContext dspctx;             ///< context providing optimized diff routines
+    AVCodecContext *avctx;         ///< codec context required for the DSPContext
+} DecimateContext;
+
+/**
+ * Return 1 if the two planes are different, 0 otherwise.
+ */
+static int diff_planes(AVFilterContext *ctx,
+                       uint8_t *cur, uint8_t *ref, int linesize,
+                       int w, int h)
+{
+    DecimateContext *decimate = ctx->priv;
+    DSPContext *dspctx = &decimate->dspctx;
+
+    int x, y;
+    int d, c = 0;
+    int t = (w/16)*(h/16)*decimate->frac;
+    DCTELEM block[8*8];
+
+    /* compute difference for blocks of 8x8 bytes */
+    for (y = 0; y < h-7; y += 4) {
+        for (x = 8; x < w-7; x += 4) {
+            dspctx->diff_pixels(block,
+                                cur+x+y*linesize,
+                                ref+x+y*linesize, linesize);
+            d = dspctx->sum_abs_dctelem(block);
+            if (d > decimate->hi)
+                return 1;
+            if (d > decimate->lo) {
+                c++;
+                if (c > t)
+                    return 1;
+            }
+        }
+    }
+    return 0;
+}
+
+/**
+ * Tell if the frame should be decimated, for example if it is no much
+ * different with respect to the reference frame ref.
+ */
+static int decimate_frame(AVFilterContext *ctx,
+                          AVFilterBufferRef *cur, AVFilterBufferRef *ref)
+{
+    DecimateContext *decimate = ctx->priv;
+    int plane;
+
+    if (decimate->max_drop_count > 0 &&
+        decimate->drop_count >= decimate->max_drop_count)
+        return 0;
+    if (decimate->max_drop_count < 0 &&
+        (decimate->drop_count-1) > decimate->max_drop_count)
+        return 0;
+
+    for (plane = 0; ref->data[plane] && ref->linesize[plane]; plane++) {
+        int vsub = plane == 1 || plane == 2 ? decimate->vsub : 0;
+        int hsub = plane == 1 || plane == 2 ? decimate->hsub : 0;
+        if (diff_planes(ctx,
+                        cur->data[plane], ref->data[plane], ref->linesize[plane],
+                        ref->video->w>>hsub, ref->video->h>>vsub))
+            return 0;
+    }
+
+    return 1;
+}
+
+static av_cold int init(AVFilterContext *ctx, const char *args)
+{
+    DecimateContext *decimate = ctx->priv;
+
+    /* set default values */
+    decimate->drop_count = decimate->max_drop_count = 0;
+    decimate->lo = 64*5;
+    decimate->hi = 64*12;
+    decimate->frac = 0.33;
+
+    if (args) {
+        char c1, c2, c3, c4;
+        int n = sscanf(args, "%d%c%d%c%d%c%f%c",
+                       &decimate->max_drop_count, &c1,
+                       &decimate->hi, &c2, &decimate->lo, &c3,
+                       &decimate->frac, &c4);
+        if (n != 1 &&
+            (n != 3 || c1 != ':') &&
+            (n != 5 || c1 != ':' || c2 != ':') &&
+            (n != 7 || c1 != ':' || c2 != ':' || c3 != ':')) {
+            av_log(ctx, AV_LOG_ERROR,
+                   "Invalid syntax for argument '%s': "
+                   "must be in the form 'max:hi:lo:frac'\n", args);
+            return AVERROR(EINVAL);
+        }
+    }
+
+    av_log(ctx, AV_LOG_VERBOSE, "max_drop_count:%d hi:%d lo:%d frac:%f\n",
+           decimate->max_drop_count, decimate->hi, decimate->lo, decimate->frac);
+
+    decimate->avctx = avcodec_alloc_context3(NULL);
+    if (!decimate->avctx)
+        return AVERROR(ENOMEM);
+    dsputil_init(&decimate->dspctx, decimate->avctx);
+
+    return 0;
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    DecimateContext *decimate = ctx->priv;
+    avfilter_unref_bufferp(&decimate->ref);
+    avcodec_close(decimate->avctx);
+    av_freep(&decimate->avctx);
+}
+
+static int query_formats(AVFilterContext *ctx)
+{
+    static const enum PixelFormat pix_fmts[] = {
+        PIX_FMT_YUV444P,      PIX_FMT_YUV422P,
+        PIX_FMT_YUV420P,      PIX_FMT_YUV411P,
+        PIX_FMT_YUV410P,      PIX_FMT_YUV440P,
+        PIX_FMT_YUVJ444P,     PIX_FMT_YUVJ422P,
+        PIX_FMT_YUVJ420P,     PIX_FMT_YUVJ440P,
+        PIX_FMT_YUVA420P,
+        PIX_FMT_NONE
+    };
+
+    ff_set_common_formats(ctx, ff_make_format_list(pix_fmts));
+
+    return 0;
+}
+
+static int config_input(AVFilterLink *inlink)
+{
+    AVFilterContext *ctx = inlink->dst;
+    DecimateContext *decimate = ctx->priv;
+    const AVPixFmtDescriptor *pix_desc = &av_pix_fmt_descriptors[inlink->format];
+    decimate->hsub = pix_desc->log2_chroma_w;
+    decimate->vsub = pix_desc->log2_chroma_h;
+
+    return 0;
+}
+
+static int start_frame(AVFilterLink *inlink, AVFilterBufferRef *picref) { return 0; }
+
+static int draw_slice(AVFilterLink *inlink, int y, int h, int slice_dir) { return 0; }
+
+static int end_frame(AVFilterLink *inlink)
+{
+    DecimateContext *decimate = inlink->dst->priv;
+    AVFilterBufferRef *cur = inlink->cur_buf;
+    AVFilterLink *outlink = inlink->dst->outputs[0];
+    int ret;
+
+    if (decimate->ref && decimate_frame(inlink->dst, cur, decimate->ref)) {
+        decimate->drop_count = FFMAX(1, decimate->drop_count+1);
+    } else {
+        avfilter_unref_buffer(decimate->ref);
+        decimate->ref = cur;
+        inlink->cur_buf = NULL;
+        decimate->drop_count = FFMIN(-1, decimate->drop_count-1);
+
+        if ((ret = ff_start_frame(outlink,
+                                  avfilter_ref_buffer(cur, ~AV_PERM_WRITE)) < 0) ||
+            (ret = ff_draw_slice(outlink, 0, inlink->h, 1)) < 0 ||
+            (ret = ff_end_frame(outlink)) < 0)
+            return ret;
+    }
+
+    av_log(inlink->dst, AV_LOG_DEBUG,
+           "%s pts:%s pts_time:%s drop_count:%d\n",
+           decimate->drop_count > 0 ? "drop" : "keep",
+           av_ts2str(cur->pts), av_ts2timestr(cur->pts, &inlink->time_base),
+           decimate->drop_count);
+
+    return 0;
+}
+
+static int request_frame(AVFilterLink *outlink)
+{
+    DecimateContext *decimate = outlink->src->priv;
+    AVFilterLink *inlink = outlink->src->inputs[0];
+    int ret;
+
+    do {
+        ret = ff_request_frame(inlink);
+    } while (decimate->drop_count > 0 && ret >= 0);
+
+    return ret;
+}
+
+AVFilter avfilter_vf_decimate = {
+    .name        = "decimate",
+    .description = NULL_IF_CONFIG_SMALL("Remove near-duplicate frames."),
+    .init        = init,
+    .uninit      = uninit,
+
+    .priv_size = sizeof(DecimateContext),
+    .query_formats = query_formats,
+
+    .inputs = (const AVFilterPad[]) {
+        {
+            .name             = "default",
+            .type             = AVMEDIA_TYPE_VIDEO,
+            .get_video_buffer = ff_null_get_video_buffer,
+            .config_props     = config_input,
+            .start_frame      = start_frame,
+            .draw_slice       = draw_slice,
+            .end_frame        = end_frame,
+            .min_perms        = AV_PERM_READ | AV_PERM_PRESERVE,
+        },
+        { .name = NULL }
+    },
+    .outputs = (const AVFilterPad[]) {
+        {
+            .name          = "default",
+            .type          = AVMEDIA_TYPE_VIDEO,
+            .request_frame = request_frame,
+        },
+        { .name = NULL }
+    },
+};