From a6f0e641bcde6d8475c5d5473ac9b4de89618fc5 Mon Sep 17 00:00:00 2001 From: Marton Balint Date: Thu, 7 Jul 2022 21:43:20 +0200 Subject: [PATCH] avfilter/vf_zscale: simplify and fix slice_params calculations Do not insist on a fixed slice height, because that can still cause overflows in corner cases as described in this comment: https://github.com/sekrit-twc/zimg/issues/177#issuecomment-1157734233 Signed-off-by: Marton Balint --- libavfilter/vf_zscale.c | 18 ++++-------------- 1 file changed, 4 insertions(+), 14 deletions(-) diff --git a/libavfilter/vf_zscale.c b/libavfilter/vf_zscale.c index 6861eef278..8e50457c6b 100644 --- a/libavfilter/vf_zscale.c +++ b/libavfilter/vf_zscale.c @@ -227,22 +227,12 @@ static int query_formats(AVFilterContext *ctx) static void slice_params(ZScaleContext *s, int out_h, int in_h) { - int slice_size; - - slice_size = (out_h + (s->nb_threads / 2)) / s->nb_threads; - if (slice_size % 2) - slice_size += 1; s->out_slice_start[0] = 0; - s->out_slice_end[0] = FFMIN(out_h, slice_size); - for (int i = 1; i < s->nb_threads - 1; i++) { - s->out_slice_start[i] = s->out_slice_end[i-1]; - s->out_slice_end[i] = s->out_slice_start[i] + slice_size; - } - - if (s->nb_threads > 1) { - s->out_slice_start[s->nb_threads - 1] = s->out_slice_end[s->nb_threads - 2]; - s->out_slice_end[s->nb_threads - 1] = out_h; + for (int i = 1; i < s->nb_threads; i++) { + int slice_end = out_h * i / s->nb_threads; + s->out_slice_end[i - 1] = s->out_slice_start[i] = FFALIGN(slice_end, 2); } + s->out_slice_end[s->nb_threads - 1] = out_h; for (int i = 0; i < s->nb_threads; i++) { s->in_slice_start[i] = s->out_slice_start[i] * in_h / (double)out_h;