vf_interlace: deprecate lowpass option

doc/filters.texi

@@ -1426,7 +1426,8 @@ a float number which specifies chroma temporal strength, defaults to
 
 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.
+halving the frame rate and preserving image height. A vertical lowpass filter
+is always applied in order to avoid twitter effects and reduce moire patterns.
 
 @example
    Original        Original             New Frame
@@ -1446,10 +1447,6 @@ It accepts the following optional parameters:
 @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

libavfilter/version.h

@@ -31,7 +31,7 @@
 
 #define LIBAVFILTER_VERSION_MAJOR  4
 #define LIBAVFILTER_VERSION_MINOR  1
-#define LIBAVFILTER_VERSION_MICRO  0
+#define LIBAVFILTER_VERSION_MICRO  1
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
                                                LIBAVFILTER_VERSION_MINOR, \
@@ -71,5 +71,8 @@
 #ifndef FF_API_NOCONST_GET_NAME
 #define FF_API_NOCONST_GET_NAME             (LIBAVFILTER_VERSION_MAJOR < 5)
 #endif
+#ifndef FF_API_INTERLACE_LOWPASS_SET
+#define FF_API_INTERLACE_LOWPASS_SET        (LIBAVFILTER_VERSION_MAJOR < 5)
+#endif
 
 #endif /* AVFILTER_VERSION_H */

libavfilter/vf_interlace.c

@@ -29,6 +29,7 @@
 #include "formats.h"
 #include "avfilter.h"
 #include "internal.h"
+#include "version.h"
 #include "video.h"
 
 enum ScanMode {
@@ -44,7 +45,9 @@ enum FieldType {
 typedef struct {
     const AVClass *class;
     enum ScanMode scan;    // top or bottom field first scanning
+#if FF_API_INTERLACE_LOWPASS_SET
     int lowpass;           // enable or disable low pass filterning
+#endif
     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;
@@ -58,8 +61,10 @@ static const AVOption options[] = {
         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),
+#if FF_API_INTERLACE_LOWPASS_SET
+    { "lowpass", "(deprecated, this option is always set)", OFFSET(lowpass),
         AV_OPT_TYPE_INT,   {.i64 = 1 },        0, 1, .flags = V },
+#endif
     { NULL }
 };
 
@@ -100,6 +105,11 @@ static int config_out_props(AVFilterLink *outlink)
     AVFilterLink *inlink = outlink->src->inputs[0];
     InterlaceContext *s = ctx->priv;
 
+#if FF_API_INTERLACE_LOWPASS_SET
+    if (!s->lowpass)
+        av_log(ctx, AV_LOG_WARNING, "This option is deprecated and always set.\n");
+#endif
+
     if (inlink->h < 2) {
         av_log(ctx, AV_LOG_ERROR, "input video height is too small\n");
         return AVERROR_INVALIDDATA;
@@ -111,15 +121,14 @@ static int config_out_props(AVFilterLink *outlink)
     // 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");
+    av_log(ctx, AV_LOG_VERBOSE, "%s interlacing\n",
+           s->scan == MODE_TFF ? "tff" : "bff");
 
     return 0;
 }
 
 static void copy_picture_field(AVFrame *src_frame, AVFrame *dst_frame,
-                               AVFilterLink *inlink, enum FieldType field_type,
-                               int lowpass)
+                               AVFilterLink *inlink, enum FieldType field_type)
 {
     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
     int vsub = desc->log2_chroma_h;
@@ -130,6 +139,8 @@ static void copy_picture_field(AVFrame *src_frame, AVFrame *dst_frame,
         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];
+        int srcp_linesize;
+        int dstp_linesize;
 
         av_assert0(linesize >= 0);
 
@@ -138,29 +149,24 @@ static void copy_picture_field(AVFrame *src_frame, AVFrame *dst_frame,
             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;
+
+        srcp_linesize = src_frame->linesize[plane] * 2;
+        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;
             }
-        } else {
-            av_image_copy_plane(dstp, dst_frame->linesize[plane] * 2,
-                                srcp, src_frame->linesize[plane] * 2,
-                                linesize, lines);
+            dstp += dstp_linesize;
+            srcp += srcp_linesize;
         }
     }
 }
@@ -204,11 +210,11 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *buf)
     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);
+    copy_picture_field(s->cur, out, inlink, tff ? FIELD_UPPER : FIELD_LOWER);
     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);
+    copy_picture_field(s->next, out, inlink, tff ? FIELD_LOWER : FIELD_UPPER);
     av_frame_free(&s->next);
 
     ret = ff_filter_frame(outlink, out);