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  1. /*
  2.  * Copyright (c) 2002 Michael Niedermayer <michaelni@gmx.at>
  3.  * Copyright (c) 2013 Paul B Mahol
  4.  *
  5.  * This file is part of FFmpeg.
  6.  *
  7.  * FFmpeg is free software; you can redistribute it and/or
  8.  * modify it under the terms of the GNU General Public
  9.  * License as published by the Free Software Foundation; either
  10.  * version 2 of the License, or (at your option) any later version.
  11.  *
  12.  * FFmpeg is distributed in the hope that it will be useful,
  13.  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14.  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15.  * GNU General Public License for more details.
  16.  *
  17.  * You should have received a copy of the GNU General Public License along
  18.  * with FFmpeg; if not, write to the Free Software
  19.  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20.  */
  21.  
  22. #include "libavutil/avassert.h"
  23. #include "libavutil/eval.h"
  24. #include "libavutil/imgutils.h"
  25. #include "libavutil/pixdesc.h"
  26. #include "libavutil/opt.h"
  27. #include "avfilter.h"
  28. #include "formats.h"
  29. #include "internal.h"
  30. #include "video.h"
  31.  
  32. #define SUB_PIXEL_BITS  8
  33. #define SUB_PIXELS      (1 << SUB_PIXEL_BITS)
  34. #define COEFF_BITS      11
  35.  
  36. #define LINEAR 0
  37. #define CUBIC  1
  38.  
  39. typedef struct PerspectiveContext {
  40.     const AVClass *class;
  41.     char *expr_str[4][2];
  42.     double ref[4][2];
  43.     int32_t (*pv)[2];
  44.     int32_t coeff[SUB_PIXELS][4];
  45.     int interpolation;
  46.     int linesize[4];
  47.     int height[4];
  48.     int hsub, vsub;
  49.     int nb_planes;
  50.     int sense;
  51.  
  52.     int (*perspective)(AVFilterContext *ctx,
  53.                        void *arg, int job, int nb_jobs);
  54. } PerspectiveContext;
  55.  
  56. #define OFFSET(x) offsetof(PerspectiveContext, x)
  57. #define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
  58.  
  59. enum PERSPECTIVESense {
  60.     PERSPECTIVE_SENSE_SOURCE      = 0, ///< coordinates give locations in source of corners of destination.
  61.     PERSPECTIVE_SENSE_DESTINATION = 1, ///< coordinates give locations in destination of corners of source.
  62. };
  63.  
  64. static const AVOption perspective_options[] = {
  65.     { "x0", "set top left x coordinate",     OFFSET(expr_str[0][0]), AV_OPT_TYPE_STRING, {.str="0"}, 0, 0, FLAGS },
  66.     { "y0", "set top left y coordinate",     OFFSET(expr_str[0][1]), AV_OPT_TYPE_STRING, {.str="0"}, 0, 0, FLAGS },
  67.     { "x1", "set top right x coordinate",    OFFSET(expr_str[1][0]), AV_OPT_TYPE_STRING, {.str="W"}, 0, 0, FLAGS },
  68.     { "y1", "set top right y coordinate",    OFFSET(expr_str[1][1]), AV_OPT_TYPE_STRING, {.str="0"}, 0, 0, FLAGS },
  69.     { "x2", "set bottom left x coordinate",  OFFSET(expr_str[2][0]), AV_OPT_TYPE_STRING, {.str="0"}, 0, 0, FLAGS },
  70.     { "y2", "set bottom left y coordinate",  OFFSET(expr_str[2][1]), AV_OPT_TYPE_STRING, {.str="H"}, 0, 0, FLAGS },
  71.     { "x3", "set bottom right x coordinate", OFFSET(expr_str[3][0]), AV_OPT_TYPE_STRING, {.str="W"}, 0, 0, FLAGS },
  72.     { "y3", "set bottom right y coordinate", OFFSET(expr_str[3][1]), AV_OPT_TYPE_STRING, {.str="H"}, 0, 0, FLAGS },
  73.     { "interpolation", "set interpolation", OFFSET(interpolation), AV_OPT_TYPE_INT, {.i64=LINEAR}, 0, 1, FLAGS, "interpolation" },
  74.     {      "linear", "", 0, AV_OPT_TYPE_CONST, {.i64=LINEAR}, 0, 0, FLAGS, "interpolation" },
  75.     {       "cubic", "", 0, AV_OPT_TYPE_CONST, {.i64=CUBIC},  0, 0, FLAGS, "interpolation" },
  76.     { "sense",   "specify the sense of the coordinates", OFFSET(sense), AV_OPT_TYPE_INT, {.i64=PERSPECTIVE_SENSE_SOURCE}, 0, 1, FLAGS, "sense"},
  77.     {       "source", "specify locations in source to send to corners in destination",
  78.                 0, AV_OPT_TYPE_CONST, {.i64=PERSPECTIVE_SENSE_SOURCE}, 0, 0, FLAGS, "sense"},
  79.     {       "destination", "specify locations in destination to send corners of source",
  80.                 0, AV_OPT_TYPE_CONST, {.i64=PERSPECTIVE_SENSE_DESTINATION}, 0, 0, FLAGS, "sense"},
  81.  
  82.     { NULL }
  83. };
  84.  
  85. AVFILTER_DEFINE_CLASS(perspective);
  86.  
  87. static int query_formats(AVFilterContext *ctx)
  88. {
  89.     static const enum AVPixelFormat pix_fmts[] = {
  90.         AV_PIX_FMT_YUVA444P, AV_PIX_FMT_YUVA422P, AV_PIX_FMT_YUVA420P,
  91.         AV_PIX_FMT_YUVJ444P, AV_PIX_FMT_YUVJ440P, AV_PIX_FMT_YUVJ422P,AV_PIX_FMT_YUVJ420P, AV_PIX_FMT_YUVJ411P,
  92.         AV_PIX_FMT_YUV444P, AV_PIX_FMT_YUV440P, AV_PIX_FMT_YUV422P, AV_PIX_FMT_YUV420P, AV_PIX_FMT_YUV411P, AV_PIX_FMT_YUV410P,
  93.         AV_PIX_FMT_GBRP, AV_PIX_FMT_GBRAP, AV_PIX_FMT_GRAY8, AV_PIX_FMT_NONE
  94.     };
  95.  
  96.     AVFilterFormats *fmts_list = ff_make_format_list(pix_fmts);
  97.     if (!fmts_list)
  98.         return AVERROR(ENOMEM);
  99.     return ff_set_common_formats(ctx, fmts_list);
  100. }
  101.  
  102. static inline double get_coeff(double d)
  103. {
  104.     double coeff, A = -0.60;
  105.  
  106.     d = fabs(d);
  107.  
  108.     if (d < 1.0)
  109.         coeff = (1.0 - (A + 3.0) * d * d + (A + 2.0) * d * d * d);
  110.     else if (d < 2.0)
  111.         coeff = (-4.0 * A + 8.0 * A * d - 5.0 * A * d * d + A * d * d * d);
  112.     else
  113.         coeff = 0.0;
  114.  
  115.     return coeff;
  116. }
  117.  
  118. static const char *const var_names[] = {   "W",   "H",        NULL };
  119. enum                                   { VAR_W, VAR_H, VAR_VARS_NB };
  120.  
  121. static int config_input(AVFilterLink *inlink)
  122. {
  123.     double x0, x1, x2, x3, x4, x5, x6, x7, x8, q;
  124.     double t0, t1, t2, t3;
  125.     AVFilterContext *ctx = inlink->dst;
  126.     PerspectiveContext *s = ctx->priv;
  127.     double (*ref)[2] = s->ref;
  128.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
  129.     double values[VAR_VARS_NB] = { [VAR_W] = inlink->w, [VAR_H] = inlink->h };
  130.     int h = inlink->h;
  131.     int w = inlink->w;
  132.     int x, y, i, j, ret;
  133.  
  134.     for (i = 0; i < 4; i++) {
  135.         for (j = 0; j < 2; j++) {
  136.             if (!s->expr_str[i][j])
  137.                 return AVERROR(EINVAL);
  138.             ret = av_expr_parse_and_eval(&s->ref[i][j], s->expr_str[i][j],
  139.                                          var_names, &values[0],
  140.                                          NULL, NULL, NULL, NULL,
  141.                                          0, 0, ctx);
  142.             if (ret < 0)
  143.                 return ret;
  144.         }
  145.     }
  146.  
  147.     s->hsub = desc->log2_chroma_w;
  148.     s->vsub = desc->log2_chroma_h;
  149.     s->nb_planes = av_pix_fmt_count_planes(inlink->format);
  150.     if ((ret = av_image_fill_linesizes(s->linesize, inlink->format, inlink->w)) < 0)
  151.         return ret;
  152.  
  153.     s->height[1] = s->height[2] = FF_CEIL_RSHIFT(inlink->h, desc->log2_chroma_h);
  154.     s->height[0] = s->height[3] = inlink->h;
  155.  
  156.     s->pv = av_realloc_f(s->pv, w * h, 2 * sizeof(*s->pv));
  157.     if (!s->pv)
  158.         return AVERROR(ENOMEM);
  159.  
  160.     switch (s->sense) {
  161.     case PERSPECTIVE_SENSE_SOURCE:
  162.         x6 = ((ref[0][0] - ref[1][0] - ref[2][0] + ref[3][0]) *
  163.               (ref[2][1] - ref[3][1]) -
  164.              ( ref[0][1] - ref[1][1] - ref[2][1] + ref[3][1]) *
  165.               (ref[2][0] - ref[3][0])) * h;
  166.         x7 = ((ref[0][1] - ref[1][1] - ref[2][1] + ref[3][1]) *
  167.               (ref[1][0] - ref[3][0]) -
  168.              ( ref[0][0] - ref[1][0] - ref[2][0] + ref[3][0]) *
  169.               (ref[1][1] - ref[3][1])) * w;
  170.         q =  ( ref[1][0] - ref[3][0]) * (ref[2][1] - ref[3][1]) -
  171.              ( ref[2][0] - ref[3][0]) * (ref[1][1] - ref[3][1]);
  172.  
  173.         x0 = q * (ref[1][0] - ref[0][0]) * h + x6 * ref[1][0];
  174.         x1 = q * (ref[2][0] - ref[0][0]) * w + x7 * ref[2][0];
  175.         x2 = q *  ref[0][0] * w * h;
  176.         x3 = q * (ref[1][1] - ref[0][1]) * h + x6 * ref[1][1];
  177.         x4 = q * (ref[2][1] - ref[0][1]) * w + x7 * ref[2][1];
  178.         x5 = q *  ref[0][1] * w * h;
  179.         x8 = q * w * h;
  180.         break;
  181.     case PERSPECTIVE_SENSE_DESTINATION:
  182.         t0 = ref[0][0] * (ref[3][1] - ref[1][1]) +
  183.              ref[1][0] * (ref[0][1] - ref[3][1]) +
  184.              ref[3][0] * (ref[1][1] - ref[0][1]);
  185.         t1 = ref[1][0] * (ref[2][1] - ref[3][1]) +
  186.              ref[2][0] * (ref[3][1] - ref[1][1]) +
  187.              ref[3][0] * (ref[1][1] - ref[2][1]);
  188.         t2 = ref[0][0] * (ref[3][1] - ref[2][1]) +
  189.              ref[2][0] * (ref[0][1] - ref[3][1]) +
  190.              ref[3][0] * (ref[2][1] - ref[0][1]);
  191.         t3 = ref[0][0] * (ref[1][1] - ref[2][1]) +
  192.              ref[1][0] * (ref[2][1] - ref[0][1]) +
  193.              ref[2][0] * (ref[0][1] - ref[1][1]);
  194.  
  195.         x0 = t0 * t1 * w * (ref[2][1] - ref[0][1]);
  196.         x1 = t0 * t1 * w * (ref[0][0] - ref[2][0]);
  197.         x2 = t0 * t1 * w * (ref[0][1] * ref[2][0] - ref[0][0] * ref[2][1]);
  198.         x3 = t1 * t2 * h * (ref[1][1] - ref[0][1]);
  199.         x4 = t1 * t2 * h * (ref[0][0] - ref[1][0]);
  200.         x5 = t1 * t2 * h * (ref[0][1] * ref[1][0] - ref[0][0] * ref[1][1]);
  201.         x6 = t1 * t2 * (ref[1][1] - ref[0][1]) +
  202.              t0 * t3 * (ref[2][1] - ref[3][1]);
  203.         x7 = t1 * t2 * (ref[0][0] - ref[1][0]) +
  204.              t0 * t3 * (ref[3][0] - ref[2][0]);
  205.         x8 = t1 * t2 * (ref[0][1] * ref[1][0] - ref[0][0] * ref[1][1]) +
  206.              t0 * t3 * (ref[2][0] * ref[3][1] - ref[2][1] * ref[3][0]);
  207.         break;
  208.     default:
  209.         av_assert0(0);
  210.     }
  211.  
  212.     for (y = 0; y < h; y++){
  213.         for (x = 0; x < w; x++){
  214.             int u, v;
  215.  
  216.             u = (int)floor(SUB_PIXELS * (x0 * x + x1 * y + x2) /
  217.                                         (x6 * x + x7 * y + x8) + 0.5);
  218.             v = (int)floor(SUB_PIXELS * (x3 * x + x4 * y + x5) /
  219.                                         (x6 * x + x7 * y + x8) + 0.5);
  220.  
  221.             s->pv[x + y * w][0] = u;
  222.             s->pv[x + y * w][1] = v;
  223.         }
  224.     }
  225.  
  226.     for (i = 0; i < SUB_PIXELS; i++){
  227.         double d = i / (double)SUB_PIXELS;
  228.         double temp[4];
  229.         double sum = 0;
  230.  
  231.         for (j = 0; j < 4; j++)
  232.             temp[j] = get_coeff(j - d - 1);
  233.  
  234.         for (j = 0; j < 4; j++)
  235.             sum += temp[j];
  236.  
  237.         for (j = 0; j < 4; j++)
  238.             s->coeff[i][j] = (int)floor((1 << COEFF_BITS) * temp[j] / sum + 0.5);
  239.     }
  240.  
  241.     return 0;
  242. }
  243.  
  244. typedef struct ThreadData {
  245.     uint8_t *dst;
  246.     int dst_linesize;
  247.     uint8_t *src;
  248.     int src_linesize;
  249.     int w, h;
  250.     int hsub, vsub;
  251. } ThreadData;
  252.  
  253. static int resample_cubic(AVFilterContext *ctx, void *arg,
  254.                           int job, int nb_jobs)
  255. {
  256.     PerspectiveContext *s = ctx->priv;
  257.     ThreadData *td = arg;
  258.     uint8_t *dst = td->dst;
  259.     int dst_linesize = td->dst_linesize;
  260.     uint8_t *src = td->src;
  261.     int src_linesize = td->src_linesize;
  262.     int w = td->w;
  263.     int h = td->h;
  264.     int hsub = td->hsub;
  265.     int vsub = td->vsub;
  266.     int start = (h * job) / nb_jobs;
  267.     int end   = (h * (job+1)) / nb_jobs;
  268.     const int linesize = s->linesize[0];
  269.     int x, y;
  270.  
  271.     for (y = start; y < end; y++) {
  272.         int sy = y << vsub;
  273.         for (x = 0; x < w; x++) {
  274.             int u, v, subU, subV, sum, sx;
  275.  
  276.             sx   = x << hsub;
  277.             u    = s->pv[sx + sy * linesize][0] >> hsub;
  278.             v    = s->pv[sx + sy * linesize][1] >> vsub;
  279.             subU = u & (SUB_PIXELS - 1);
  280.             subV = v & (SUB_PIXELS - 1);
  281.             u  >>= SUB_PIXEL_BITS;
  282.             v  >>= SUB_PIXEL_BITS;
  283.  
  284.             if (u > 0 && v > 0 && u < w - 2 && v < h - 2){
  285.                 const int index = u + v*src_linesize;
  286.                 const int a = s->coeff[subU][0];
  287.                 const int b = s->coeff[subU][1];
  288.                 const int c = s->coeff[subU][2];
  289.                 const int d = s->coeff[subU][3];
  290.  
  291.                 sum = s->coeff[subV][0] * (a * src[index - 1 -     src_linesize] + b * src[index - 0 -     src_linesize]  +
  292.                                       c *      src[index + 1 -     src_linesize] + d * src[index + 2 -     src_linesize]) +
  293.                       s->coeff[subV][1] * (a * src[index - 1                   ] + b * src[index - 0                   ]  +
  294.                                       c *      src[index + 1                   ] + d * src[index + 2                   ]) +
  295.                       s->coeff[subV][2] * (a * src[index - 1 +     src_linesize] + b * src[index - 0 +     src_linesize]  +
  296.                                       c *      src[index + 1 +     src_linesize] + d * src[index + 2 +     src_linesize]) +
  297.                       s->coeff[subV][3] * (a * src[index - 1 + 2 * src_linesize] + b * src[index - 0 + 2 * src_linesize]  +
  298.                                       c *      src[index + 1 + 2 * src_linesize] + d * src[index + 2 + 2 * src_linesize]);
  299.             } else {
  300.                 int dx, dy;
  301.  
  302.                 sum = 0;
  303.  
  304.                 for (dy = 0; dy < 4; dy++) {
  305.                     int iy = v + dy - 1;
  306.  
  307.                     if (iy < 0)
  308.                         iy = 0;
  309.                     else if (iy >= h)
  310.                         iy = h-1;
  311.                     for (dx = 0; dx < 4; dx++) {
  312.                         int ix = u + dx - 1;
  313.  
  314.                         if (ix < 0)
  315.                             ix = 0;
  316.                         else if (ix >= w)
  317.                             ix = w - 1;
  318.  
  319.                         sum += s->coeff[subU][dx] * s->coeff[subV][dy] * src[ ix + iy * src_linesize];
  320.                     }
  321.                 }
  322.             }
  323.  
  324.             sum = (sum + (1<<(COEFF_BITS * 2 - 1))) >> (COEFF_BITS * 2);
  325.             sum = av_clip_uint8(sum);
  326.             dst[x + y * dst_linesize] = sum;
  327.         }
  328.     }
  329.     return 0;
  330. }
  331.  
  332. static int resample_linear(AVFilterContext *ctx, void *arg,
  333.                            int job, int nb_jobs)
  334. {
  335.     PerspectiveContext *s = ctx->priv;
  336.     ThreadData *td = arg;
  337.     uint8_t *dst = td->dst;
  338.     int dst_linesize = td->dst_linesize;
  339.     uint8_t *src = td->src;
  340.     int src_linesize = td->src_linesize;
  341.     int w = td->w;
  342.     int h = td->h;
  343.     int hsub = td->hsub;
  344.     int vsub = td->vsub;
  345.     int start = (h * job) / nb_jobs;
  346.     int end   = (h * (job+1)) / nb_jobs;
  347.     const int linesize = s->linesize[0];
  348.     int x, y;
  349.  
  350.     for (y = start; y < end; y++){
  351.         int sy = y << vsub;
  352.         for (x = 0; x < w; x++){
  353.             int u, v, subU, subV, sum, sx, index, subUI, subVI;
  354.  
  355.             sx   = x << hsub;
  356.             u    = s->pv[sx + sy * linesize][0] >> hsub;
  357.             v    = s->pv[sx + sy * linesize][1] >> vsub;
  358.             subU = u & (SUB_PIXELS - 1);
  359.             subV = v & (SUB_PIXELS - 1);
  360.             u  >>= SUB_PIXEL_BITS;
  361.             v  >>= SUB_PIXEL_BITS;
  362.  
  363.             index = u + v * src_linesize;
  364.             subUI = SUB_PIXELS - subU;
  365.             subVI = SUB_PIXELS - subV;
  366.  
  367.             if ((unsigned)u < (unsigned)(w - 1)){
  368.                 if((unsigned)v < (unsigned)(h - 1)){
  369.                     sum = subVI * (subUI * src[index] + subU * src[index + 1]) +
  370.                           subV  * (subUI * src[index + src_linesize] + subU * src[index + src_linesize + 1]);
  371.                     sum = (sum + (1 << (SUB_PIXEL_BITS * 2 - 1)))>> (SUB_PIXEL_BITS * 2);
  372.                 } else {
  373.                     if (v < 0)
  374.                         v = 0;
  375.                     else
  376.                         v = h - 1;
  377.                     index = u + v * src_linesize;
  378.                     sum   = subUI * src[index] + subU * src[index + 1];
  379.                     sum   = (sum + (1 << (SUB_PIXEL_BITS - 1))) >> SUB_PIXEL_BITS;
  380.                 }
  381.             } else {
  382.                 if (u < 0)
  383.                     u = 0;
  384.                 else
  385.                     u = w - 1;
  386.                 if ((unsigned)v < (unsigned)(h - 1)){
  387.                     index = u + v * src_linesize;
  388.                     sum   = subVI * src[index] + subV * src[index + src_linesize];
  389.                     sum   = (sum + (1 << (SUB_PIXEL_BITS - 1))) >> SUB_PIXEL_BITS;
  390.                 } else {
  391.                     if (v < 0)
  392.                         v = 0;
  393.                     else
  394.                         v = h - 1;
  395.                     index = u + v * src_linesize;
  396.                     sum   = src[index];
  397.                 }
  398.             }
  399.  
  400.             sum = av_clip_uint8(sum);
  401.             dst[x + y * dst_linesize] = sum;
  402.         }
  403.     }
  404.     return 0;
  405. }
  406.  
  407. static av_cold int init(AVFilterContext *ctx)
  408. {
  409.     PerspectiveContext *s = ctx->priv;
  410.  
  411.     switch (s->interpolation) {
  412.     case LINEAR: s->perspective = resample_linear; break;
  413.     case CUBIC:  s->perspective = resample_cubic;  break;
  414.     }
  415.  
  416.     return 0;
  417. }
  418.  
  419. static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
  420. {
  421.     AVFilterContext *ctx = inlink->dst;
  422.     AVFilterLink *outlink = ctx->outputs[0];
  423.     PerspectiveContext *s = ctx->priv;
  424.     AVFrame *out;
  425.     int plane;
  426.  
  427.     out = ff_get_video_buffer(outlink, outlink->w, outlink->h);
  428.     if (!out) {
  429.         av_frame_free(&frame);
  430.         return AVERROR(ENOMEM);
  431.     }
  432.     av_frame_copy_props(out, frame);
  433.  
  434.     for (plane = 0; plane < s->nb_planes; plane++) {
  435.         int hsub = plane == 1 || plane == 2 ? s->hsub : 0;
  436.         int vsub = plane == 1 || plane == 2 ? s->vsub : 0;
  437.         ThreadData td = {.dst = out->data[plane],
  438.                          .dst_linesize = out->linesize[plane],
  439.                          .src = frame->data[plane],
  440.                          .src_linesize = frame->linesize[plane],
  441.                          .w = s->linesize[plane],
  442.                          .h = s->height[plane],
  443.                          .hsub = hsub,
  444.                          .vsub = vsub };
  445.         ctx->internal->execute(ctx, s->perspective, &td, NULL, FFMIN(td.h, ctx->graph->nb_threads));
  446.     }
  447.  
  448.     av_frame_free(&frame);
  449.     return ff_filter_frame(outlink, out);
  450. }
  451.  
  452. static av_cold void uninit(AVFilterContext *ctx)
  453. {
  454.     PerspectiveContext *s = ctx->priv;
  455.  
  456.     av_freep(&s->pv);
  457. }
  458.  
  459. static const AVFilterPad perspective_inputs[] = {
  460.     {
  461.         .name         = "default",
  462.         .type         = AVMEDIA_TYPE_VIDEO,
  463.         .filter_frame = filter_frame,
  464.         .config_props = config_input,
  465.     },
  466.     { NULL }
  467. };
  468.  
  469. static const AVFilterPad perspective_outputs[] = {
  470.     {
  471.         .name = "default",
  472.         .type = AVMEDIA_TYPE_VIDEO,
  473.     },
  474.     { NULL }
  475. };
  476.  
  477. AVFilter ff_vf_perspective = {
  478.     .name          = "perspective",
  479.     .description   = NULL_IF_CONFIG_SMALL("Correct the perspective of video."),
  480.     .priv_size     = sizeof(PerspectiveContext),
  481.     .init          = init,
  482.     .uninit        = uninit,
  483.     .query_formats = query_formats,
  484.     .inputs        = perspective_inputs,
  485.     .outputs       = perspective_outputs,
  486.     .priv_class    = &perspective_class,
  487.     .flags         = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC | AVFILTER_FLAG_SLICE_THREADS,
  488. };
  489.