lavfi: new interlace filter

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

Changelog

@@ -10,6 +10,7 @@ version 10:
 - new avconv options -filter_script and -filter_complex_script, which allow a
   filtergraph description to be read from a file
 - uniform options syntax across all filters
+- new interlace filter
 
 
 version 9:

configure

@@ -1881,6 +1881,7 @@ frei0r_filter_extralibs='$ldl'
 frei0r_src_filter_deps="frei0r dlopen strtok_r"
 frei0r_src_filter_extralibs='$ldl'
 hqdn3d_filter_deps="gpl"
+interlace_filter_deps="gpl"
 resample_filter_deps="avresample"
 ocv_filter_deps="libopencv"
 scale_filter_deps="swscale"

doc/filters.texi

@@ -1235,6 +1235,36 @@ a float number which specifies chroma temporal strength, defaults to
 @var{luma_tmp}*@var{chroma_spatial}/@var{luma_spatial}
 @end table
 
+@section interlace
+
+Simple interlacing filter from progressive contents. This interleaves upper (or
+lower) lines from odd frames with lower (or upper) lines from even frames,
+halving the frame rate and preserving image height.
+
+@example
+   Original        Original             New Frame
+   Frame 'j'      Frame 'j+1'             (tff)
+  ==========      ===========       ==================
+    Line 0  -------------------->    Frame 'j' Line 0
+    Line 1          Line 1  ---->   Frame 'j+1' Line 1
+    Line 2 --------------------->    Frame 'j' Line 2
+    Line 3          Line 3  ---->   Frame 'j+1' Line 3
+     ...             ...                   ...
+New Frame + 1 will be generated by Frame 'j+2' and Frame 'j+3' and so on
+@end example
+
+It accepts the following optional parameters:
+
+@table @option
+@item scan
+determines whether the interlaced frame is taken from the even (tff - default)
+or odd (bff) lines of the progressive frame.
+
+@item lowpass
+Enable (default) or disable the vertical lowpass filter to avoid twitter
+interlacing and reduce moire patterns.
+@end table
+
 @section lut, lutrgb, lutyuv
 
 Compute a look-up table for binding each pixel component input value

libavfilter/Makefile

@@ -56,6 +56,7 @@ OBJS-$(CONFIG_FREI0R_FILTER)                 += vf_frei0r.o
 OBJS-$(CONFIG_GRADFUN_FILTER)                += vf_gradfun.o
 OBJS-$(CONFIG_HFLIP_FILTER)                  += vf_hflip.o
 OBJS-$(CONFIG_HQDN3D_FILTER)                 += vf_hqdn3d.o
+OBJS-$(CONFIG_INTERLACE_FILTER)              += vf_interlace.o
 OBJS-$(CONFIG_LUT_FILTER)                    += vf_lut.o
 OBJS-$(CONFIG_LUTRGB_FILTER)                 += vf_lut.o
 OBJS-$(CONFIG_LUTYUV_FILTER)                 += vf_lut.o

libavfilter/allfilters.c

@@ -76,6 +76,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER(GRADFUN,        gradfun,        vf);
     REGISTER_FILTER(HFLIP,          hflip,          vf);
     REGISTER_FILTER(HQDN3D,         hqdn3d,         vf);
+    REGISTER_FILTER(INTERLACE,      interlace,      vf);
     REGISTER_FILTER(LUT,            lut,            vf);
     REGISTER_FILTER(LUTRGB,         lutrgb,         vf);
     REGISTER_FILTER(LUTYUV,         lutyuv,         vf);

libavfilter/vf_interlace.c

@@ -0,0 +1,252 @@
+/*
+ * 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
+ * progressive to interlaced content filter, inspired by heavy debugging of tinterlace filter
+ */
+
+#include "libavutil/common.h"
+#include "libavutil/opt.h"
+#include "libavutil/imgutils.h"
+#include "libavutil/avassert.h"
+
+#include "formats.h"
+#include "avfilter.h"
+#include "internal.h"
+#include "video.h"
+
+enum ScanMode {
+    MODE_TFF = 0,
+    MODE_BFF = 1,
+};
+
+enum FieldType {
+    FIELD_UPPER = 0,
+    FIELD_LOWER = 1,
+};
+
+typedef struct {
+    const AVClass *class;
+    enum ScanMode scan;    // top or bottom field first scanning
+    int lowpass;           // enable or disable low pass filterning
+    AVFrame *cur, *next;   // the two frames from which the new one is obtained
+    int got_output;        // signal an output frame is reday to request_frame()
+} InterlaceContext;
+
+#define OFFSET(x) offsetof(InterlaceContext, x)
+#define V AV_OPT_FLAG_VIDEO_PARAM
+static const AVOption options[] = {
+    { "scan", "scanning mode", OFFSET(scan),
+        AV_OPT_TYPE_INT,   {.i64 = MODE_TFF }, 0, 1, .flags = V, .unit = "scan" },
+    { "tff", "top field first", 0,
+        AV_OPT_TYPE_CONST, {.i64 = MODE_TFF }, INT_MIN, INT_MAX, .flags = V, .unit = "scan" },
+    { "bff", "bottom field first", 0,
+        AV_OPT_TYPE_CONST, {.i64 = MODE_BFF }, INT_MIN, INT_MAX, .flags = V, .unit = "scan" },
+    { "lowpass", "enable vertical low-pass filter", OFFSET(lowpass),
+        AV_OPT_TYPE_INT,   {.i64 = 1 },        0, 1, .flags = V },
+    { NULL }
+};
+
+static const AVClass class = {
+    .class_name = "interlace filter",
+    .item_name  = av_default_item_name,
+    .option     = options,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+
+
+static const enum AVPixelFormat formats_supported[] = {
+    AV_PIX_FMT_YUV420P,  AV_PIX_FMT_YUV422P,  AV_PIX_FMT_YUV444P,
+    AV_PIX_FMT_YUV444P,  AV_PIX_FMT_YUV410P,  AV_PIX_FMT_YUVA420P,
+    AV_PIX_FMT_GRAY8,    AV_PIX_FMT_YUVJ420P, AV_PIX_FMT_YUVJ422P,
+    AV_PIX_FMT_YUVJ444P, AV_PIX_FMT_YUVJ440P, AV_PIX_FMT_NONE
+};
+
+static int query_formats(AVFilterContext *ctx)
+{
+    ff_set_common_formats(ctx, ff_make_format_list(formats_supported));
+    return 0;
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    InterlaceContext *s = ctx->priv;
+
+    av_frame_free(&s->cur);
+    av_frame_free(&s->next);
+
+    av_opt_free(s);
+}
+
+static int config_out_props(AVFilterLink *outlink)
+{
+    AVFilterContext *ctx = outlink->src;
+    AVFilterLink *inlink = outlink->src->inputs[0];
+    InterlaceContext *s = ctx->priv;
+
+    if (inlink->h < 2) {
+        av_log(ctx, AV_LOG_ERROR, "input video height is too small\n");
+        return AVERROR_INVALIDDATA;
+    }
+    // same input size
+    outlink->w = inlink->w;
+    outlink->h = inlink->h;
+    outlink->time_base = inlink->time_base;
+    // half framerate
+    outlink->time_base.num *= 2;
+
+    av_log(ctx, AV_LOG_VERBOSE, "%s interlacing %s lowpass filter\n",
+           s->scan == MODE_TFF ? "tff" : "bff", (s->lowpass) ? "with" : "without");
+
+    return 0;
+}
+
+static void copy_picture_field(AVFrame *src_frame, AVFrame *dst_frame,
+                               AVFilterLink *inlink, enum FieldType field_type,
+                               int lowpass)
+{
+    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
+    int vsub = desc->log2_chroma_h;
+    int plane, i, j;
+
+    for (plane = 0; plane < desc->nb_components; plane++) {
+        int lines = (plane == 1 || plane == 2) ? inlink->h >> vsub : inlink->h;
+        int linesize = av_image_get_linesize(inlink->format, inlink->w, plane);
+        uint8_t *dstp = dst_frame->data[plane];
+        const uint8_t *srcp = src_frame->data[plane];
+
+        av_assert0(linesize >= 0);
+
+        lines /= 2;
+        if (field_type == FIELD_LOWER)
+            srcp += src_frame->linesize[plane];
+        if (field_type == FIELD_LOWER)
+            dstp += dst_frame->linesize[plane];
+        if (lowpass) {
+            int srcp_linesize = src_frame->linesize[plane] * 2;
+            int dstp_linesize = dst_frame->linesize[plane] * 2;
+            for (j = lines; j > 0; j--) {
+                const uint8_t *srcp_above = srcp - src_frame->linesize[plane];
+                const uint8_t *srcp_below = srcp + src_frame->linesize[plane];
+                if (j == lines)
+                    srcp_above = srcp; // there is no line above
+                if (j == 1)
+                    srcp_below = srcp; // there is no line below
+                for (i = 0; i < linesize; i++) {
+                    // this calculation is an integer representation of
+                    // '0.5 * current + 0.25 * above + 0.25 + below'
+                    // '1 +' is for rounding.
+                    dstp[i] = (1 + srcp[i] + srcp[i] + srcp_above[i] + srcp_below[i]) >> 2;
+                }
+                dstp += dstp_linesize;
+                srcp += srcp_linesize;
+            }
+        } else {
+            av_image_copy_plane(dstp, dst_frame->linesize[plane] * 2,
+                                srcp, src_frame->linesize[plane] * 2,
+                                linesize, lines);
+        }
+    }
+}
+
+static int filter_frame(AVFilterLink *inlink, AVFrame *buf)
+{
+    AVFilterContext *ctx = inlink->dst;
+    AVFilterLink *outlink = ctx->outputs[0];
+    InterlaceContext *s = ctx->priv;
+    AVFrame *out;
+    int tff, ret;
+
+    av_frame_free(&s->cur);
+    s->cur  = s->next;
+    s->next = buf;
+
+    /* we need at least two frames */
+    if (!s->cur || !s->next)
+        return 0;
+
+    tff = (s->scan == MODE_TFF);
+    out = ff_get_video_buffer(outlink, outlink->w, outlink->h);
+    if (!out)
+        return AVERROR(ENOMEM);
+
+    av_frame_copy_props(out, s->cur);
+    out->interlaced_frame = 1;
+    out->top_field_first  = tff;
+    out->pts             /= 2;  // adjust pts to new framerate
+
+    /* copy upper/lower field from cur */
+    copy_picture_field(s->cur, out, inlink, tff ? FIELD_UPPER : FIELD_LOWER, s->lowpass);
+    av_frame_free(&s->cur);
+
+    /* copy lower/upper field from next */
+    copy_picture_field(s->next, out, inlink, tff ? FIELD_LOWER : FIELD_UPPER, s->lowpass);
+    av_frame_free(&s->next);
+
+    ret = ff_filter_frame(outlink, out);
+    s->got_output = 1;
+
+    return ret;
+}
+
+static int request_frame(AVFilterLink *outlink)
+{
+    AVFilterContext *ctx = outlink->src;
+    InterlaceContext *s  = ctx->priv;
+    int ret = 0;
+
+    s->got_output = 0;
+    while (ret >= 0 && !s->got_output)
+        ret = ff_request_frame(ctx->inputs[0]);
+
+    return ret;
+}
+
+static const AVFilterPad inputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_VIDEO,
+        .filter_frame = filter_frame,
+    },
+    { NULL }
+};
+
+static const AVFilterPad outputs[] = {
+    {
+        .name          = "default",
+        .type          = AVMEDIA_TYPE_VIDEO,
+        .config_props  = config_out_props,
+        .request_frame = request_frame,
+    },
+    { NULL }
+};
+
+AVFilter avfilter_vf_interlace = {
+    .name          = "interlace",
+    .description   = NULL_IF_CONFIG_SMALL("Convert progressive video into interlaced."),
+    .uninit        = uninit,
+
+    .priv_class    = &class,
+    .priv_size     = sizeof(InterlaceContext),
+    .query_formats = query_formats,
+
+    .inputs        = inputs,
+    .outputs       = outputs,
+};
+