@@ -5760,6 +5760,13 @@ Number of frames after which a given frame's contribution to the

 statistics is halved (i.e., it contributes only 0.5 to it's

 classification). The default of 0 means that all frames seen are given

 full weight of 1.0 forever.

+@item analyze_interlaced_flag

+When this is not 0 then idet will use the specified number of frames to determine

+if the interlaced flag is accurate, it will not count undetermined frames.

+If the flag is found to be accurate it will be used without any further

+computations, if it is found to be inaccuarte it will be cleared without any

+further computations. This allows inserting the idet filter as a low computational

+method to clean up the interlaced flag

 @end table

 @section il

@@ -34,6 +34,7 @@ static const AVOption idet_options[] = {

     { "prog_thres", "set progressive threshold", OFFSET(progressive_threshold), AV_OPT_TYPE_FLOAT, {.dbl = 1.5},  -1, FLT_MAX, FLAGS },

     { "rep_thres",  "set repeat threshold",      OFFSET(repeat_threshold),      AV_OPT_TYPE_FLOAT, {.dbl = 3.0},  -1, FLT_MAX, FLAGS },

     { "half_life", "half life of cumulative statistics", OFFSET(half_life),     AV_OPT_TYPE_FLOAT, {.dbl = 0.0},  -1, INT_MAX, FLAGS },

+    { "analyze_interlaced_flag", "set number of frames to use to determine if the interlace flag is accurate", OFFSET(analyze_interlaced_flag), AV_OPT_TYPE_INT, {.i64 = 0 }, 0, INT_MAX, FLAGS },

     { NULL }

 };

@@ -235,6 +236,19 @@ static int filter_frame(AVFilterLink *link, AVFrame *picref)

     AVFilterContext *ctx = link->dst;

     IDETContext *idet = ctx->priv;

+    // initial frame(s) and not interlaced, just pass through for

+    // the analyze_interlaced_flag mode

+    if (idet->analyze_interlaced_flag &&

+        !picref->interlaced_frame &&

+        !idet->next) {

+        return ff_filter_frame(ctx->outputs[0], picref);

+    }

+    if (idet->analyze_interlaced_flag_done) {

+        if (picref->interlaced_frame && idet->interlaced_flag_accuracy < 0)

+            picref->interlaced_frame = 0;

+        return ff_filter_frame(ctx->outputs[0], picref);

+    }

+

     if (idet->prev)

         av_frame_free(&idet->prev);

     idet->prev = idet->cur;

@@ -256,7 +270,30 @@ static int filter_frame(AVFilterLink *link, AVFrame *picref)

             ff_idet_init_x86(idet, 1);

     }

-    filter(ctx);

+    if (idet->analyze_interlaced_flag) {

+        if (idet->cur->interlaced_frame) {

+            idet->cur->interlaced_frame = 0;

+            filter(ctx);

+            if (idet->last_type == PROGRESSIVE) {

+                idet->interlaced_flag_accuracy --;

+                idet->analyze_interlaced_flag --;

+            } else if (idet->last_type != UNDETERMINED) {

+                idet->interlaced_flag_accuracy ++;

+                idet->analyze_interlaced_flag --;

+            }

+            if (idet->analyze_interlaced_flag == 1) {

+                ff_filter_frame(ctx->outputs[0], av_frame_clone(idet->cur));

+

+                if (idet->next->interlaced_frame && idet->interlaced_flag_accuracy < 0)

+                    idet->next->interlaced_frame = 0;

+                idet->analyze_interlaced_flag_done = 1;

+                av_log(ctx, AV_LOG_INFO, "Final flag accuracy %d\n", idet->interlaced_flag_accuracy);

+                return ff_filter_frame(ctx->outputs[0], av_frame_clone(idet->next));

+            }

+        }

+    } else {

+        filter(ctx);

+    }

     return ff_filter_frame(ctx->outputs[0], av_frame_clone(idet->cur));

 }

@@ -274,7 +311,7 @@ static int request_frame(AVFilterLink *link)

         ret = ff_request_frame(link->src->inputs[0]);

-        if (ret == AVERROR_EOF && idet->cur) {

+        if (ret == AVERROR_EOF && idet->cur && !idet->analyze_interlaced_flag_done) {

             AVFrame *next = av_frame_clone(idet->next);

             if (!next)

@@ -63,6 +63,10 @@ typedef struct {

     AVFrame *prev;

     ff_idet_filter_func filter_line;

+    int interlaced_flag_accuracy;

+    int analyze_interlaced_flag;

+    int analyze_interlaced_flag_done;

+

     const AVPixFmtDescriptor *csp;

     int eof;

 } IDETContext;