fate: add mpdecimate test.

tests/fate/filter-video.mak

@@ -329,6 +329,9 @@ FATE_FILTER-$(call ALLYES, TESTSRC_FILTER SINE_FILTER CONCAT_FILTER) += fate-fil
 fate-filter-concat: tests/data/filtergraphs/concat
 fate-filter-concat: CMD = framecrc -filter_complex_script $(TARGET_PATH)/tests/data/filtergraphs/concat
 
+FATE_FILTER-$(call ALLYES, TESTSRC2_FILTER FPS_FILTER MPDECIMATE_FILTER) += fate-filter-mpdecimate
+fate-filter-mpdecimate: CMD = framecrc -lavfi testsrc2=r=2:d=10,fps=3,mpdecimate -r 3 -pix_fmt yuv420p
+
 FATE_FILTER_VSYNTH-$(call ALLYES, FORMAT_FILTER SPLIT_FILTER ALPHAEXTRACT_FILTER ALPHAMERGE_FILTER) += fate-filter-alphaextract_alphamerge_rgb
 fate-filter-alphaextract_alphamerge_rgb: tests/data/filtergraphs/alphamerge_alphaextract_rgb
 fate-filter-alphaextract_alphamerge_rgb: CMD = framecrc -c:v pgmyuv -i $(SRC) -filter_complex_script $(TARGET_PATH)/tests/data/filtergraphs/alphamerge_alphaextract_rgb

tests/ref/fate/filter-mpdecimate

+#tb 0: 1/3
+0,          0,          0,        1,   115200, 0x3744b3ed
+0,          2,          2,        1,   115200, 0x6e318ba0
+0,          3,          3,        1,   115200, 0x48d65876
+0,          5,          5,        1,   115200, 0x9087e4f1
+0,          6,          6,        1,   115200, 0xc58d5c94
+0,          8,          8,        1,   115200, 0x8c4ad4f4
+0,          9,          9,        1,   115200, 0xf96f6755
+0,         11,         11,        1,   115200, 0x90beb7ba
+0,         12,         12,        1,   115200, 0xa8f4f31b
+0,         14,         14,        1,   115200, 0x21441a03
+0,         15,         15,        1,   115200, 0x393b3494
+0,         17,         17,        1,   115200, 0xc7aeec1d
+0,         18,         18,        1,   115200, 0x2bd24a0e
+0,         20,         20,        1,   115200, 0xea66d804
+0,         21,         21,        1,   115200, 0x237953c3
+0,         23,         23,        1,   115200, 0xff98a9b1
+0,         24,         24,        1,   115200, 0x056d40ca
+0,         26,         26,        1,   115200, 0xa4374737
+0,         27,         27,        1,   115200, 0x3eaa3ae8
+0,         29,         29,        1,   115200, 0x7551e9ee