[FFmpeg-devel] [PATCH] libavfilter/vf_scale: Ensure scaled video is divisible by n

[Paul B Mahol]

On Mon, Aug 5, 2019 at 1:31 PM Lars Kiesow <lkiesow at uos.de> wrote:

> Hi everyone,
> this is now open for nearly a month with no more comments or change
> requests. Anything else I should do to get this merged?
> Best regards,
>

Yes, ping it more frequently, until its merged.
Waiting for months will not help as people are busy.


> Lars
>
>
> On Mon,  8 Jul 2019 17:43:40 +0200
> Lars Kiesow <lkiesow at uos.de> wrote:
>
> > This patch adds a new option to the scale filter which ensures that
> > the output resolution is divisible by the given integer when used
> > together with `force_original_aspect_ratio`. This works similar to
> > using `-n` in the `w` and `h` options.
> >
> > This option respects the value set for `force_original_aspect_ratio`,
> > increasing or decreasing the resolution accordingly.
> >
> > The use case for this is to set a fixed target resolution using `w`
> > and `h`, to use the `force_original_aspect_ratio` option to make sure
> > that the video always fits in the defined bounding box regardless of
> > aspect ratio, but to also make sure that the calculated output
> > resolution is divisible by n so in can be encoded with certain
> > encoders/options if that is required.
> >
> > Signed-off-by: Lars Kiesow <lkiesow at uos.de>
> > ---
> >  doc/filters.texi       | 12 ++++++++++++
> >  libavfilter/vf_scale.c | 13 ++++++++++++-
> >  2 files changed, 24 insertions(+), 1 deletion(-)
> >
> > diff --git a/doc/filters.texi b/doc/filters.texi
> > index ee6a93ffbf..2de71d9820 100644
> > --- a/doc/filters.texi
> > +++ b/doc/filters.texi
> > @@ -15231,6 +15231,18 @@ Please note that this is a different thing
> > than specifying -1 for @option{w} or @option{h}, you still need to
> > specify the output resolution for this option to work.
> >
> > + at item force_divisible_by Ensures that the output resolution is
> > divisible by the +given integer when used together with
> > @option{force_original_aspect_ratio}. This +works similar to using -n
> > in the @option{w} and @option{h} options. +
> > +This option respects the value set for
> > @option{force_original_aspect_ratio}, +increasing or decreasing the
> > resolution accordingly. This may slightly modify +the video's aspect
> > ration. +
> > +This can be handy, for example, if you want to have a video fit
> > within a defined +resolution using the
> > @option{force_original_aspect_ratio} option but have +encoder
> > restrictions when it comes to width or height. +
> >  @end table
> >
> >  The values of the @option{w} and @option{h} options are expressions
> > diff --git a/libavfilter/vf_scale.c b/libavfilter/vf_scale.c
> > index 7aebf56ad8..3ce6cdd1d5 100644
> > --- a/libavfilter/vf_scale.c
> > +++ b/libavfilter/vf_scale.c
> > @@ -86,6 +86,7 @@ typedef struct ScaleContext {
> >      int in_v_chr_pos;
> >
> >      int force_original_aspect_ratio;
> > +    int force_divisible_by;
> >
> >      int nb_slices;
> >
> > @@ -237,7 +238,8 @@ static int config_props(AVFilterLink *outlink)
> >          goto fail;
> >
> >      /* Note that force_original_aspect_ratio may overwrite the
> > previous set
> > -     * dimensions so that it is not divisible by the set factors
> > anymore. */
> > +     * dimensions so that it is not divisible by the set factors
> > anymore
> > +     * unless force_divisible_by is defined as well */
> >      if (scale->force_original_aspect_ratio) {
> >          int tmp_w = av_rescale(h, inlink->w, inlink->h);
> >          int tmp_h = av_rescale(w, inlink->h, inlink->w);
> > @@ -245,9 +247,17 @@ static int config_props(AVFilterLink *outlink)
> >          if (scale->force_original_aspect_ratio == 1) {
> >               w = FFMIN(tmp_w, w);
> >               h = FFMIN(tmp_h, h);
> > +             if (scale->force_divisible_by > 1) {
> > +                 w = w / scale->force_divisible_by *
> > scale->force_divisible_by;
> > +                 h = h / scale->force_divisible_by *
> > scale->force_divisible_by;
> > +             }
> >          } else {
> >               w = FFMAX(tmp_w, w);
> >               h = FFMAX(tmp_h, h);
> > +             if (scale->force_divisible_by > 1) {
> > +                 w = ceil(w / (float)scale->force_divisible_by) *
> > scale->force_divisible_by;
> > +                 h = ceil(h / (float)scale->force_divisible_by) *
> > scale->force_divisible_by;
> > +             }
> >          }
> >      }
> >
> > @@ -600,6 +610,7 @@ static const AVOption scale_options[] = {
> >      { "disable",  NULL, 0, AV_OPT_TYPE_CONST, {.i64 = 0 }, 0, 0,
> > FLAGS, "force_oar" }, { "decrease", NULL, 0, AV_OPT_TYPE_CONST, {.i64
> > = 1 }, 0, 0, FLAGS, "force_oar" }, { "increase", NULL, 0,
> > AV_OPT_TYPE_CONST, {.i64 = 2 }, 0, 0, FLAGS, "force_oar" },
> > +    { "force_divisible_by", "enforce that the output resolution is
> > divisible by a defined integer when force_original_aspect_ratio is
> > used", OFFSET(force_divisible_by), AV_OPT_TYPE_INT, { .i64 = 1}, 1,
> > 256, FLAGS }, { "param0", "Scaler param 0",
> > OFFSET(param[0]),  AV_OPT_TYPE_DOUBLE, { .dbl = SWS_PARAM_DEFAULT  },
> > INT_MIN, INT_MAX, FLAGS }, { "param1", "Scaler param 1",
> > OFFSET(param[1]),  AV_OPT_TYPE_DOUBLE, { .dbl = SWS_PARAM_DEFAULT  },
> > INT_MIN, INT_MAX, FLAGS }, { "nb_slices", "set the number of slices
> > (debug purpose only)", OFFSET(nb_slices), AV_OPT_TYPE_INT, { .i64 =
> > 0 }, 0, INT_MAX, FLAGS },
>
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