lavfi: adding dejudder filter to remove judder produced by partially telecined material.

Signed-off-by: Nicholas Robbins <nickrobbins@yahoo.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Changelog

@@ -27,6 +27,7 @@ version <next>
 - Mirillis FIC video decoder
 - Support DNx444
 - libx265 encoder
+- dejudder filter
 
 
 version 2.1:

doc/filters.texi

@@ -3215,6 +3215,38 @@ Set whether or not chroma is considered in the metric calculations. Default is
 @code{1}.
 @end table
 
+@section dejudder
+
+Remove judder produced by partially interlaced telecined content.
+
+Judder can be introduced, for instance, by @ref{pullup} filter. If the original
+source was partially telecined content then the output of @code{pullup,dejudder}
+will have a variable frame rate. May change the recorded frame rate of the
+container. Aside from that change, this filter will not affect constant frame
+rate video.
+
+The option available in this filter is:
+@table @option
+
+@item cycle
+Specify the length of the window over which the judder repeats.
+
+Accepts any interger greater than 1. Useful values are:
+@table @samp
+
+@item 4
+If the original was telecined from 24 to 30 fps (Film to NTSC).
+
+@item 5
+If the original was telecined from 25 to 30 fps (PAL to NTSC).
+
+@item 20
+If a mixture of the two.
+@end table
+
+The default is @samp{4}.
+@end table
+
 @section delogo
 
 Suppress a TV station logo by a simple interpolation of the surrounding
@@ -6633,6 +6665,7 @@ On this example the input file being processed is compared with the
 reference file @file{ref_movie.mpg}. The PSNR of each individual frame
 is stored in @file{stats.log}.
 
+@anchor{pullup}
 @section pullup
 
 Pulldown reversal (inverse telecine) filter, capable of handling mixed

libavfilter/Makefile

@@ -127,6 +127,7 @@ OBJS-$(CONFIG_CROPDETECT_FILTER)             += vf_cropdetect.o
 OBJS-$(CONFIG_CURVES_FILTER)                 += vf_curves.o
 OBJS-$(CONFIG_DCTDNOIZ_FILTER)               += vf_dctdnoiz.o
 OBJS-$(CONFIG_DECIMATE_FILTER)               += vf_decimate.o
+OBJS-$(CONFIG_DEJUDDER_FILTER)               += vf_dejudder.o
 OBJS-$(CONFIG_DELOGO_FILTER)                 += vf_delogo.o
 OBJS-$(CONFIG_DESHAKE_FILTER)                += vf_deshake.o
 OBJS-$(CONFIG_DRAWBOX_FILTER)                += vf_drawbox.o

libavfilter/allfilters.c

@@ -122,6 +122,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER(CURVES,         curves,         vf);
     REGISTER_FILTER(DCTDNOIZ,       dctdnoiz,       vf);
     REGISTER_FILTER(DECIMATE,       decimate,       vf);
+    REGISTER_FILTER(DEJUDDER,       dejudder,       vf);
     REGISTER_FILTER(DELOGO,         delogo,         vf);
     REGISTER_FILTER(DESHAKE,        deshake,        vf);
     REGISTER_FILTER(DRAWBOX,        drawbox,        vf);

libavfilter/vf_dejudder.c

@@ -0,0 +1,187 @@
+/*
+ * Copyright (c) 2014 Nicholas Robbins
+ *
+ * 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
+ * remove judder in video stream
+ *
+ * Algorithm:
+ *    - If the old packets had PTS of old_pts[i]. Replace these with new
+ *      value based on the running average of the last n=cycle frames. So
+ *
+ *      new_pts[i] = Sum(k=i-n+1, i, old_pts[k])/n
+ *                        + (old_pts[i]-old_pts[i-n])*(n-1)/2n
+ *
+ *      For any repeating pattern of length n of judder this will produce
+ *      an even progression of PTS's.
+ *
+ *    - In order to avoid calculating this sum ever frame, a running tally
+ *      is maintained in ctx->new_pts. Each frame the new term at the start
+ *      of the sum is added, the one and the end is removed, and the offset
+ *      terms (second line in formula above) are recalculated.
+ *
+ *    - To aid in this a ringbuffer of the last n-2 PTS's is maintained in
+ *      ctx->ringbuff. With the indices of the first two and last two entries
+ *      stored in i1, i2, i3, & i4.
+ *
+ *    - To ensure that the new PTS's are integers, time_base is divided
+ *      by 2n. This removes the division in the new_pts calculation.
+ *
+ *    - frame_rate is also multiplied by 2n to allow the frames to fall
+ *      where they may in what may now be a VFR output. This produces more
+ *      even output then setting frame_rate=1/0 in practice.
+ */
+
+#include "libavutil/opt.h"
+#include "libavutil/mathematics.h"
+#include "avfilter.h"
+#include "internal.h"
+#include "video.h"
+
+typedef struct {
+    const AVClass *class;
+    int64_t *ringbuff;
+    int i1, i2, i3, i4;
+    int64_t new_pts;
+    int start_count;
+
+    /* options */
+    int cycle;
+} DejudderContext;
+
+#define OFFSET(x) offsetof(DejudderContext, x)
+#define FLAGS AV_OPT_FLAG_FILTERING_PARAM | AV_OPT_FLAG_VIDEO_PARAM
+
+static const AVOption dejudder_options[] = {
+    {"cycle", "set the length of the cycle to use for dejuddering",
+        OFFSET(cycle), AV_OPT_TYPE_INT, {.i64 = 4}, 2, 240, .flags = FLAGS},
+    {NULL}
+};
+
+AVFILTER_DEFINE_CLASS(dejudder);
+
+static int config_out_props(AVFilterLink *outlink)
+{
+    AVFilterContext *ctx = outlink->src;
+    DejudderContext *dj = ctx->priv;
+    AVFilterLink *inlink = outlink->src->inputs[0];
+
+    outlink->time_base = av_mul_q(inlink->time_base, av_make_q(1, 2 * dj->cycle));
+    outlink->frame_rate = av_mul_q(inlink->frame_rate, av_make_q(2 * dj->cycle, 1));
+
+    av_log(ctx, AV_LOG_VERBOSE, "cycle:%d\n", dj->cycle);
+
+    return 0;
+}
+
+static av_cold int dejudder_init(AVFilterContext *ctx)
+{
+    DejudderContext *dj = ctx->priv;
+
+    dj->ringbuff = av_mallocz(sizeof(*dj->ringbuff) * (dj->cycle+2));
+    if (!dj->ringbuff)
+        return AVERROR(ENOMEM);
+
+    dj->new_pts = 0;
+    dj->i1 = 0;
+    dj->i2 = 1;
+    dj->i3 = 2;
+    dj->i4 = 3;
+    dj->start_count = dj->cycle + 2;
+
+    return 0;
+}
+
+static av_cold void dejudder_uninit(AVFilterContext *ctx)
+{
+    DejudderContext *dj = ctx->priv;
+
+    av_freep(&(dj->ringbuff));
+}
+
+static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
+{
+    int k;
+    AVFilterContext *ctx  = inlink->dst;
+    AVFilterLink *outlink = ctx->outputs[0];
+    DejudderContext *dj   = ctx->priv;
+    int64_t *judbuff      = dj->ringbuff;
+    int64_t next_pts      = frame->pts;
+    int64_t offset;
+
+    if (next_pts == AV_NOPTS_VALUE)
+        return ff_filter_frame(outlink, frame);
+
+    if (dj->start_count) {
+        dj->start_count--;
+        dj->new_pts = next_pts * 2 * dj->cycle;
+    } else {
+        if (next_pts < judbuff[dj->i2]) {
+            offset = next_pts + judbuff[dj->i3] - judbuff[dj->i4] - judbuff[dj->i1];
+            for (k = 0; k < dj->cycle + 2; k++)
+                judbuff[k] += offset;
+        }
+        dj->new_pts += (dj->cycle - 1) * (judbuff[dj->i3] - judbuff[dj->i1])
+                    + (dj->cycle + 1) * (next_pts - judbuff[dj->i4]);
+    }
+
+    judbuff[dj->i2] = next_pts;
+    dj->i1 = dj->i2;
+    dj->i2 = dj->i3;
+    dj->i3 = dj->i4;
+    dj->i4 = (dj->i4 + 1) % (dj->cycle + 2);
+
+    frame->pts = dj->new_pts;
+
+    for (k = 0; k < dj->cycle + 2; k++)
+        av_log(ctx, AV_LOG_DEBUG, "%"PRId64"\t", judbuff[k]);
+    av_log(ctx, AV_LOG_DEBUG, "next=%"PRId64", new=%"PRId64"\n", next_pts, frame->pts);
+
+    return ff_filter_frame(outlink, frame);
+}
+
+static const AVFilterPad dejudder_inputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_VIDEO,
+        .filter_frame = filter_frame,
+    },
+    { NULL }
+};
+
+static const AVFilterPad dejudder_outputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_VIDEO,
+        .config_props = config_out_props,
+    },
+    { NULL }
+};
+
+AVFilter ff_vf_dejudder = {
+    .name        = "dejudder",
+    .description = NULL_IF_CONFIG_SMALL("Remove judder produced by pullup."),
+    .priv_size   = sizeof(DejudderContext),
+    .priv_class  = &dejudder_class,
+    .inputs      = dejudder_inputs,
+    .outputs     = dejudder_outputs,
+    .init        = dejudder_init,
+    .uninit      = dejudder_uninit,
+};