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avfilter/cropdetect: add option for initial skip

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The cropdetect filter, at present, skips the first two frames. This
behaviour is hardcoded.

New option 'skip' allows users to change this. Convenient for when
input is a single image or a trimmed video stream.

Default is kept at 2 to preserve current behaviour.
This commit is contained in:
Gyan Doshi 2020-12-08 18:52:37 +05:30
parent b9b719fedc
commit 7777e5119a
2 changed files with 10 additions and 4 deletions
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4
doc/filters.texi
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@ -8899,6 +8899,10 @@ The value which the width/height should be divisible by. It defaults to
get only even dimensions (needed for 4:2:2 video). 16 is best when
encoding to most video codecs.
@item skip
Set the number of initial frames for which evaluation is skipped.
Default is 2. Range is 0 to INT_MAX.
@item reset_count, reset
Set the counter that determines after how many frames cropdetect will
reset the previously detected largest video area and start over to

10
libavfilter/vf_cropdetect.c
View File

@ -37,6 +37,7 @@ typedef struct CropDetectContext {
int x1, y1, x2, y2;
float limit;
int round;
int skip;
int reset_count;
int frame_nb;
int max_pixsteps[4];
@ -127,10 +128,10 @@ static av_cold int init(AVFilterContext *ctx)
{
CropDetectContext *s = ctx->priv;
s->frame_nb = -2;
s->frame_nb = -1 * s->skip;
av_log(ctx, AV_LOG_VERBOSE, "limit:%f round:%d reset_count:%d\n",
s->limit, s->round, s->reset_count);
av_log(ctx, AV_LOG_VERBOSE, "limit:%f round:%d skip:%d reset_count:%d\n",
s->limit, s->round, s->skip, s->reset_count);
return 0;
}
@ -167,7 +168,7 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
int outliers, last_y;
int limit = lrint(s->limit);
// ignore first 2 frames - they may be empty
// ignore first s->skip frames
if (++s->frame_nb > 0) {
metadata = &frame->metadata;
@ -247,6 +248,7 @@ static const AVOption cropdetect_options[] = {
{ "limit", "Threshold below which the pixel is considered black", OFFSET(limit), AV_OPT_TYPE_FLOAT, { .dbl = 24.0/255 }, 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 },
{ "skip", "Number of initial frames to skip", OFFSET(skip), AV_OPT_TYPE_INT, { .i64 = 2 }, 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 },
{ "max_outliers", "Threshold count of outliers", OFFSET(max_outliers),AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, FLAGS },
{ NULL }