avfilter/blend: clip expression output to pixel depth

Clip integer expression results in the double domain before storing them. This keeps high-bit-depth samples within their declared range and gives NaN and infinities defined behavior while preserving float formats.

Fixes issue #24121.

libavfilter/blend.h

@@ -78,6 +78,7 @@ typedef struct SliceParams {
 typedef struct FilterParams {
     enum BlendMode mode;
     double opacity;
+    unsigned max_value;
     AVExpr **e;
     char *expr_str;
     void (*blend)(const uint8_t *top, ptrdiff_t top_linesize,

libavfilter/vf_blend.c

@@ -129,7 +129,7 @@ static const AVOption blend_options[] = {
 
 FRAMESYNC_DEFINE_CLASS(blend, BlendContext, fs);
 
-#define DEFINE_BLEND_EXPR(type, name, div)                                     \
+#define DEFINE_BLEND_EXPR(type, name, div, clip)                               \
 static void blend_expr_## name(const uint8_t *_top, ptrdiff_t top_linesize,          \
                                const uint8_t *_bottom, ptrdiff_t bottom_linesize,    \
                                uint8_t *_dst, ptrdiff_t dst_linesize,                \
@@ -153,7 +153,8 @@ static void blend_expr_## name(const uint8_t *_top, ptrdiff_t top_linesize,
             values[VAR_X]      = x;                                            \
             values[VAR_TOP]    = values[VAR_A] = top[x];                       \
             values[VAR_BOTTOM] = values[VAR_B] = bottom[x];                    \
-            dst[x] = av_expr_eval(e, values, NULL);                            \
+            double value = av_expr_eval(e, values, NULL);                     \
+            dst[x] = clip ? av_clipd(value, 0, param->max_value) : value;      \
         }                                                                      \
         dst    += dst_linesize;                                                \
         top    += top_linesize;                                                \
@@ -161,9 +162,9 @@ static void blend_expr_## name(const uint8_t *_top, ptrdiff_t top_linesize,
     }                                                                          \
 }
 
-DEFINE_BLEND_EXPR(uint8_t, 8bit, 1)
-DEFINE_BLEND_EXPR(uint16_t, 16bit, 2)
-DEFINE_BLEND_EXPR(float, 32bit, 4)
+DEFINE_BLEND_EXPR(uint8_t, 8bit, 1, 1)
+DEFINE_BLEND_EXPR(uint16_t, 16bit, 2, 1)
+DEFINE_BLEND_EXPR(float, 32bit, 4, 0)
 
 static int filter_slice(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs)
 {
@@ -306,6 +307,8 @@ static int config_params(AVFilterContext *ctx)
     for (int plane = 0; plane < FF_ARRAY_ELEMS(s->params); plane++) {
         FilterParams *param = &s->params[plane];
 
+        param->max_value = UINT32_MAX >> (32 - s->depth);
+
         if (s->all_mode >= 0)
             param->mode = s->all_mode;
         if (s->all_opacity < 1)

tests/fate/filter-video.mak

@@ -382,6 +382,9 @@ FATE_FILTER_VSYNTH_PGMYUV-$(CONFIG_SWAPRECT_FILTER) += $(FATE_SWAPRECT)
 FATE_FILTER_VSYNTH_PGMYUV-$(CONFIG_TBLEND_FILTER) += fate-filter-tblend
 fate-filter-tblend: CMD = framecrc -c:v pgmyuv -i $(SRC) -vf tblend=all_mode=difference128
 
+FATE_FILTER-$(call FILTERFRAMECRC, BLEND FORMAT NULLSRC SCALE SPLIT) += fate-filter-blend-expr-clipping
+fate-filter-blend-expr-clipping: CMD = framecrc -lavfi "nullsrc=s=1x1:d=1:r=1,format=gray10,split[a][b];[a][b]blend=c0_expr=1024,scale" -pix_fmt gray10le
+
 FATE_FILTER_VSYNTH_PGMYUV-$(CONFIG_TELECINE_FILTER) += fate-filter-telecine
 fate-filter-telecine: CMD = framecrc -c:v pgmyuv -i $(SRC) -vf telecine
 

tests/ref/fate/filter-blend-expr-clipping

@@ -0,0 +1,6 @@
+#tb 0: 1/1
+#media_type 0: video
+#codec_id 0: rawvideo
+#dimensions 0: 1x1
+#sar 0: 1/1
+0,          0,          0,        1,        2, 0x02010102