On date Wednesday 2015-10-07 08:54:59 +0200, Jean Delvare encoded:
> The original interpolation algorithm behaved poorly on the borders and
> did not even guarantee continuity at the borders. For this reason, a
> second interpolation/blending pass was required on the borders to make
> them seamless.
>
> However, since the interpolation algorithm was improved in June 2013,
> the border issues no longer exist. The new algorithm does guarantee
> continuity at the borders, making the second pass useless. A larger
> band always increases the cumulated interpolation error. In most cases
> it also increases the average interpolation error, even though the
> samples in the band are only partially interpolated.
>
> For this reason I would like to get rid of the "band" parameter. As a
> first step, let's change its default value from 4 to 1 and document it
> as deprecated.
>
> I have benchmarked this change on a combination of input sources and
> realistic logo areas. Lowering the band value from 4 to 1 resulted in
> 8 to 39 % less interpolation error per frame (or 1 to 34 % less
> interpolation error per luma sample.)
>
> Signed-off-by: Jean Delvare <jdelv...@suse.de>
> ---
> doc/filters.texi | 4 +++-
> libavfilter/vf_delogo.c | 11 +++++++++--
> 2 files changed, 12 insertions(+), 3 deletions(-)
>
> --- ffmpeg.orig/doc/filters.texi 2015-10-02 11:41:24.035943770 +0200
> +++ ffmpeg/doc/filters.texi 2015-10-02 12:02:08.231484828 +0200
> @@ -4590,7 +4590,9 @@ specified.
>
> @item band, t
> Specify the thickness of the fuzzy edge of the rectangle (added to
> -@var{w} and @var{h}). The default value is 4.
> +@var{w} and @var{h}). The default value is 1. This option is
> +deprecated, setting higher values should no longer be necessary and
> +is not recommended.
>
> @item show
> When set to 1, a green rectangle is drawn on the screen to simplify
> --- ffmpeg.orig/libavfilter/vf_delogo.c 2015-10-02 11:41:24.035943770
> +0200
> +++ ffmpeg/libavfilter/vf_delogo.c 2015-10-07 08:45:39.037203764 +0200
> @@ -165,8 +165,9 @@ static const AVOption delogo_options[]=
> { "y", "set logo y position", OFFSET(y), AV_OPT_TYPE_INT, {
> .i64 = -1 }, -1, INT_MAX, FLAGS },
> { "w", "set logo width", OFFSET(w), AV_OPT_TYPE_INT, {
> .i64 = -1 }, -1, INT_MAX, FLAGS },
> { "h", "set logo height", OFFSET(h), AV_OPT_TYPE_INT, {
> .i64 = -1 }, -1, INT_MAX, FLAGS },
> - { "band", "set delogo area band size", OFFSET(band), AV_OPT_TYPE_INT, {
> .i64 = 4 }, 1, INT_MAX, FLAGS },
> - { "t", "set delogo area band size", OFFSET(band), AV_OPT_TYPE_INT, {
> .i64 = 4 }, 1, INT_MAX, FLAGS },
> + /* Actual default value for band/t is 1, set in init */
> + { "band", "set delogo area band size", OFFSET(band), AV_OPT_TYPE_INT, {
> .i64 = 0 }, 0, INT_MAX, FLAGS },
> + { "t", "set delogo area band size", OFFSET(band), AV_OPT_TYPE_INT, {
> .i64 = 0 }, 0, INT_MAX, FLAGS },
> { "show", "show delogo area", OFFSET(show), AV_OPT_TYPE_BOOL,{
> .i64 = 0 }, 0, 1, FLAGS },
> { NULL }
> };
> @@ -201,6 +202,12 @@ static av_cold int init(AVFilterContext
> CHECK_UNSET_OPT(w);
> CHECK_UNSET_OPT(h);
>
> + if (s->band == 0) { /* Unset, use default */
> + av_log(ctx, AV_LOG_WARNING, "Note: default band value was changed
> from 4 to 1.\n");
> + s->band = 1;
> + } else if (s->band != 1) {
> + av_log(ctx, AV_LOG_WARNING, "Option band is deprecated.\n");
> + }
> av_log(ctx, AV_LOG_VERBOSE, "x:%d y:%d, w:%d h:%d band:%d show:%d\n",
> s->x, s->y, s->w, s->h, s->band, s->show);
LGTM. BTW, if you want to drop the band option, you could ifdef it so
that it will be dropt at the next lavfi major bump.
--
FFmpeg = Friendly and Fundamental Meaningless Programmable Enlightened God
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