avfilter/vf_cropdetect: extend limit to cover 16bit pixel formats

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavfilter/vf_cropdetect.c

@@ -238,7 +238,7 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
 #define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
 
 static const AVOption cropdetect_options[] = {
-    { "limit", "Threshold below which the pixel is considered black", OFFSET(limit),       AV_OPT_TYPE_INT, { .i64 = 24 }, 0, 255, FLAGS },
+    { "limit", "Threshold below which the pixel is considered black", OFFSET(limit),       AV_OPT_TYPE_INT, { .i64 = 24 }, 0, 65535, FLAGS },
     { "round", "Value by which the width/height should be divisible", OFFSET(round),       AV_OPT_TYPE_INT, { .i64 = 16 }, 0, INT_MAX, FLAGS },
     { "reset", "Recalculate the crop area after this many frames",    OFFSET(reset_count), AV_OPT_TYPE_INT, { .i64 = 0 },  0, INT_MAX, FLAGS },
     { "reset_count", "Recalculate the crop area after this many frames",OFFSET(reset_count),AV_OPT_TYPE_INT,{ .i64 = 0 },  0, INT_MAX, FLAGS },