[FFmpeg-devel] [PATCH] avfilter/cropdetect: add option for initial skip

[Gyan Doshi]

Thanks. Pushed as 7777e5119ad3377e2c4cb20a7aff56448d035b55

On 08-12-2020 07:02 pm, Paul B Mahol wrote:
> lgtm
>
> On Tue, Dec 8, 2020 at 2:29 PM Gyan Doshi <ffmpeg at gyani.pro> wrote:
>
>> 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.
>> ---
>>   doc/filters.texi            |  4 ++++
>>   libavfilter/vf_cropdetect.c | 10 ++++++----
>>   2 files changed, 10 insertions(+), 4 deletions(-)
>>
>> diff --git a/doc/filters.texi b/doc/filters.texi
>> index 62d6e26a02..d9f606604e 100644
>> --- a/doc/filters.texi
>> +++ b/doc/filters.texi
>> @@ -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.
>>
>> + at 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
>> diff --git a/libavfilter/vf_cropdetect.c b/libavfilter/vf_cropdetect.c
>> index 7c7d0b953a..5ae87cad2d 100644
>> --- a/libavfilter/vf_cropdetect.c
>> +++ b/libavfilter/vf_cropdetect.c
>> @@ -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 }
>> --
>> 2.27.0
>>
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