[FFmpeg-devel] [PATCH v1] avfilter/vf_freezedetect: add force_discard option to force discard freeze/non-freeze frame

[Marton Balint]

On Mon, 30 Sep 2019, lance.lmwang at gmail.com wrote:

> From: Limin Wang <lance.lmwang at gmail.com>
>
> How to tested it, please try with the following command:
> ./ffmpeg  -f lavfi -i "smptebars=duration=5:size=1280x720:rate=30,freezedetect=d=1:f=0"  -f null -
> frame=  150 fps=0.0 q=-0.0 Lsize=N/A time=00:00:05.00 bitrate=N/A speed= 232x
>
> ./ffmpeg  -f lavfi -i "smptebars=duration=5:size=1280x720:rate=30,freezedetect=d=1:f=-1"  -f null -
> frame=  120 fps=0.0 q=-0.0 Lsize=N/A time=00:00:04.00 bitrate=N/A speed= 211x
>
> ./ffmpeg  -f lavfi -i "smptebars=duration=5:size=1280x720:rate=30,freezedetect=d=1:f=1"  -f null -
> frame=   30 fps=0.0 q=-0.0 Lsize=N/A time=00:00:01.00 bitrate=N/A speed=93.9x
>
> Signed-off-by: Limin Wang <lance.lmwang at gmail.com>
> ---
> doc/filters.texi              | 10 ++++++++++
> libavfilter/vf_freezedetect.c | 23 ++++++++++++++++++++++-
> 2 files changed, 32 insertions(+), 1 deletion(-)
>
> diff --git a/doc/filters.texi b/doc/filters.texi
> index 6ed1c8fa75..2be8b93c53 100644
> --- a/doc/filters.texi
> +++ b/doc/filters.texi
> @@ -10678,6 +10678,8 @@ timestamp of the first frame of the freeze. The
> @code{lavfi.freezedetect.freeze_duration} and
> @code{lavfi.freezedetect.freeze_end} metadata keys are set on the first frame
> after the freeze.
> +In addition, you can choose to discard the freeze/non-freezee frames instead of
> +report by metadata.
> 
> The filter accepts the following options:
> 
> @@ -10689,6 +10691,14 @@ specified value) or as a difference ratio between 0 and 1. Default is -60dB, or
> 
> @item duration, d
> Set freeze duration until notification (default is 2 seconds).
> +
> + at item force_discard, f
> +Set force to discard or keep freeze frame.
> + 0:  do nothing
> +-1:  discard non-freeze frame
> + 1:  discard freeze frame

I don't see how discarding non-frozen frames is useful in any way, so that 
option should be removed unless you have something sensible in mind.

I would also like to point out that freezedetect does not buffer any 
frames, so the first few frames (the detection interval) of a freeze won't 
be dropped, which is not what the user might expect when it wants to drop 
frozen frames. At least you should document this.

> +
> +Default is 0
> @end table
> 
> @anchor{frei0r}
> diff --git a/libavfilter/vf_freezedetect.c b/libavfilter/vf_freezedetect.c
> index cc086afee6..fc08c235f7 100644
> --- a/libavfilter/vf_freezedetect.c
> +++ b/libavfilter/vf_freezedetect.c
> @@ -45,6 +45,9 @@ typedef struct FreezeDetectContext {
>
>     double noise;
>     int64_t duration;            ///< minimum duration of frozen frame until notification
> +
> +    int force_discard;           ///< 0: no discard, -1: discard non-freeze frame, 1: discard freeze frame
> +    int drop_count;

Why don't you simply use s->frozen to see if the current frame needs to be 
dropped or not? That would be much easier to follow.

> } FreezeDetectContext;
> 
> #define OFFSET(x) offsetof(FreezeDetectContext, x)
> @@ -56,6 +59,8 @@ static const AVOption freezedetect_options[] = {
>     { "noise",               "set noise tolerance",                       OFFSET(noise),  AV_OPT_TYPE_DOUBLE,   {.dbl=0.001},     0,       1.0, V|F },
>     { "d",                   "set minimum duration in seconds",        OFFSET(duration),  AV_OPT_TYPE_DURATION, {.i64=2000000},   0, INT64_MAX, V|F },
>     { "duration",            "set minimum duration in seconds",        OFFSET(duration),  AV_OPT_TYPE_DURATION, {.i64=2000000},   0, INT64_MAX, V|F },
> +    { "f",                   "set frame discard",                      OFFSET(force_discard), AV_OPT_TYPE_INT,  {.i64=0},         -1,        1, V|F },
> +    { "force_discard",       "set frame discard",                      OFFSET(force_discard), AV_OPT_TYPE_INT,  {.i64=0},         -1,        1, V|F },

A name like "discard" should be enough, no need for short version, it is 
only used for consistency with silencedetect.

>
>     {NULL}
> };
> @@ -115,6 +120,7 @@ static int config_input(AVFilterLink *inlink)
>     if (!s->sad)
>         return AVERROR(EINVAL);
> 
> +    s->drop_count = 0;
>     return 0;
> }
> 
> @@ -184,10 +190,22 @@ static int activate(AVFilterContext *ctx)
>                     set_meta(s, frame, "lavfi.freezedetect.freeze_end", av_ts2timestr(frame->pts, &inlink->time_base));
>                 }
>                 s->frozen = frozen;
> +                if ( s->force_discard > 0 && frozen)
> +                    s->drop_count++;
> +                else if ( s->force_discard < 0 && frozen && s->drop_count < 0) {
> +                    s->drop_count = 0;
> +                }
> +            } else {
> +                if ( s->force_discard < 0)
> +                    s->drop_count--;
>             }
>         }
>
>         if (!frozen) {
> +            if (s->force_discard > 0) {
> +                s->drop_count = 0;
> +            } else if ( s->force_discard < 0)
> +                s->drop_count--;
>             av_frame_free(&s->reference_frame);
>             s->reference_frame = av_frame_clone(frame);
>             s->reference_n = s->n;
> @@ -196,7 +214,10 @@ static int activate(AVFilterContext *ctx)
>                 return AVERROR(ENOMEM);
>             }
>         }
> -        return ff_filter_frame(outlink, frame);
> +        if (s->drop_count > 0 || s->drop_count < 0) {
> +            av_frame_free(&frame);
> +        } else
> +            return ff_filter_frame(outlink, frame);
>     }
>
>     FF_FILTER_FORWARD_STATUS(inlink, outlink);
> -- 
> 2.21.0
>

Regards,
Marton