lavfi/tinterlace: support symbolic names for the parameter

Also deprecate the use of numerical values.

doc/filters.texi

@@ -2778,31 +2778,31 @@ This filter accepts a single parameter specifying the mode. Available
 modes are:
 
 @table @samp
-@item 0
+@item merge, 0
 Move odd frames into the upper field, even into the lower field,
 generating a double height frame at half framerate.
 
-@item 1
+@item drop_odd, 1
 Only output even frames, odd frames are dropped, generating a frame with
 unchanged height at half framerate.
 
-@item 2
+@item drop_even, 2
 Only output odd frames, even frames are dropped, generating a frame with
 unchanged height at half framerate.
 
-@item 3
+@item pad, 3
 Expand each frame to full height, but pad alternate lines with black,
 generating a frame with double height at the same input framerate.
 
-@item 4
+@item interleave_top, 4
 Interleave the upper field from odd frames with the lower field from
 even frames, generating a frame with unchanged height at half framerate.
 
-@item 5
+@item interleave_bottom, 5
 Interleave the lower field from odd frames with the upper field from
 even frames, generating a frame with unchanged height at half framerate.
 
-@item 6
+@item interlacex2, 6
 Double frame rate with unchanged height. Frames are inserted each
 containing the second temporal field from the previous input frame and
 the first temporal field from the next input frame. This mode relies on
@@ -2810,7 +2810,10 @@ the top_field_first flag. Useful for interlaced video displays with no
 field synchronisation.
 @end table
 
-Default mode is 0.
+Numeric values are deprecated but are accepted for backward
+compatibility reasons.
+
+Default mode is @code{merge}.
 
 @section transpose
 

libavfilter/version.h

@@ -30,7 +30,7 @@
 
 #define LIBAVFILTER_VERSION_MAJOR  2
 #define LIBAVFILTER_VERSION_MINOR 72
-#define LIBAVFILTER_VERSION_MICRO 101
+#define LIBAVFILTER_VERSION_MICRO 102
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
                                                LIBAVFILTER_VERSION_MINOR, \

libavfilter/vf_tinterlace.c

@@ -29,8 +29,29 @@
 #include "avfilter.h"
 #include "internal.h"
 
+enum TInterlaceMode {
+    MODE_MERGE = 0,
+    MODE_DROP_EVEN,
+    MODE_DROP_ODD,
+    MODE_PAD,
+    MODE_INTERLEAVE_TOP,
+    MODE_INTERLEAVE_BOTTOM,
+    MODE_INTERLACEX2,
+};
+
+static const char *tinterlace_mode_str[] = {
+    "merge",
+    "drop_even",
+    "drop_odd",
+    "pad",
+    "interleave_top",
+    "interleave_bottom",
+    "interlacex2",
+    NULL
+};
+
 typedef struct {
-    int mode;                   ///< interlace mode selected
+    enum TInterlaceMode mode;   ///< interlace mode selected
     int frame;                  ///< number of the output frame
     int vsub;                   ///< chroma vertical subsampling
     AVFilterBufferRef *cur;
@@ -62,16 +83,32 @@ static int query_formats(AVFilterContext *ctx)
 static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
 {
     TInterlaceContext *tinterlace = ctx->priv;
-    int n;
-    tinterlace->mode = 0;
+    int i;
+    char c;
 
-    if (args) {
-        n = sscanf(args, "%d", &tinterlace->mode);
+    tinterlace->mode = MODE_MERGE;
 
-        if (n != 1 || tinterlace->mode < 0 || tinterlace->mode > 6) {
-            av_log(ctx, AV_LOG_ERROR,
-                   "Invalid mode '%s', use an integer between 0 and 6\n", args);
-            return AVERROR(EINVAL);
+    if (args) {
+        if (sscanf(args, "%d%c", (int *)&tinterlace->mode, &c) == 1) {
+            if (tinterlace->mode > 6) {
+                av_log(ctx, AV_LOG_ERROR,
+                       "Invalid mode '%s', use an integer between 0 and 6\n", args);
+                return AVERROR(EINVAL);
+            }
+
+            av_log(ctx, AV_LOG_WARNING,
+                   "Using numeric constant is deprecated, use symbolic values\n");
+        } else {
+            for (i = 0; tinterlace_mode_str[i]; i++) {
+                if (!strcmp(tinterlace_mode_str[i], args)) {
+                    tinterlace->mode = i;
+                    break;
+                }
+            }
+            if (!tinterlace_mode_str[i]) {
+                av_log(ctx, AV_LOG_ERROR, "Invalid argument '%s'\n", args);
+                return AVERROR(EINVAL);
+            }
         }
     }
 
@@ -97,10 +134,10 @@ static int config_out_props(AVFilterLink *outlink)
 
     tinterlace->vsub = desc->log2_chroma_h;
     outlink->w = inlink->w;
-    outlink->h = tinterlace->mode == 0 || tinterlace->mode == 3 ?
+    outlink->h = tinterlace->mode == MODE_MERGE || tinterlace->mode == MODE_PAD ?
         inlink->h*2 : inlink->h;
 
-    if (tinterlace->mode == 3) {
+    if (tinterlace->mode == MODE_PAD) {
         uint8_t black[4] = { 16, 128, 128, 16 };
         int i, ret;
         if (ff_fmt_is_in(outlink->format, full_scale_yuvj_pix_fmts))
@@ -117,8 +154,8 @@ static int config_out_props(AVFilterLink *outlink)
                    tinterlace->black_linesize[i] * h);
         }
     }
-    av_log(ctx, AV_LOG_INFO, "mode:%d h:%d -> h:%d\n",
-           tinterlace->mode, inlink->h, outlink->h);
+    av_log(ctx, AV_LOG_INFO, "mode:%s h:%d -> h:%d\n",
+           tinterlace_mode_str[tinterlace->mode], inlink->h, outlink->h);
 
     return 0;
 }
@@ -185,7 +222,7 @@ static void end_frame(AVFilterLink *inlink)
         return;
 
     switch (tinterlace->mode) {
-    case 0: /* move the odd frame into the upper field of the new image, even into
+    case MODE_MERGE: /* move the odd frame into the upper field of the new image, even into
              * the lower field, generating a double-height video at half framerate */
         out = avfilter_get_video_buffer(outlink, AV_PERM_WRITE, outlink->w, outlink->h);
         avfilter_copy_buffer_ref_props(out, cur);
@@ -206,14 +243,14 @@ static void end_frame(AVFilterLink *inlink)
         avfilter_unref_bufferp(&tinterlace->next);
         break;
 
-    case 1: /* only output even frames, odd  frames are dropped; height unchanged, half framerate */
-    case 2: /* only output odd  frames, even frames are dropped; height unchanged, half framerate */
-        out = avfilter_ref_buffer(tinterlace->mode == 2 ? cur : next, AV_PERM_READ);
+    case MODE_DROP_ODD:  /* only output even frames, odd  frames are dropped; height unchanged, half framerate */
+    case MODE_DROP_EVEN: /* only output odd  frames, even frames are dropped; height unchanged, half framerate */
+        out = avfilter_ref_buffer(tinterlace->mode == MODE_DROP_EVEN ? cur : next, AV_PERM_READ);
         avfilter_unref_bufferp(&tinterlace->next);
         break;
 
-    case 3: /* expand each frame to double height, but pad alternate
-             * lines with black; framerate unchanged */
+    case MODE_PAD: /* expand each frame to double height, but pad alternate
+                    * lines with black; framerate unchanged */
         out = avfilter_get_video_buffer(outlink, AV_PERM_WRITE, outlink->w, outlink->h);
         avfilter_copy_buffer_ref_props(out, cur);
         out->video->h = outlink->h;
@@ -233,9 +270,9 @@ static void end_frame(AVFilterLink *inlink)
 
         /* interleave upper/lower lines from odd frames with lower/upper lines from even frames,
          * halving the frame rate and preserving image height */
-    case 4: /* top    field first */
-    case 5: /* bottom field first */
-        tff = tinterlace->mode == 4;
+    case MODE_INTERLEAVE_TOP:    /* top    field first */
+    case MODE_INTERLEAVE_BOTTOM: /* bottom field first */
+        tff = tinterlace->mode == MODE_INTERLEAVE_TOP;
         out = avfilter_get_video_buffer(outlink, AV_PERM_WRITE, outlink->w, outlink->h);
         avfilter_copy_buffer_ref_props(out, cur);
         out->video->interlaced = 1;
@@ -253,7 +290,7 @@ static void end_frame(AVFilterLink *inlink)
                            tff ? FIELD_LOWER : FIELD_UPPER, 1, tff ? FIELD_LOWER : FIELD_UPPER);
         avfilter_unref_bufferp(&tinterlace->next);
         break;
-    case 6: /* re-interlace preserving image height, double frame rate */
+    case MODE_INTERLACEX2: /* re-interlace preserving image height, double frame rate */
         /* output current frame first */
         out = avfilter_ref_buffer(cur, AV_PERM_READ);
         out->video->interlaced = 1;