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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 <cus@passwd.hu>
This commit is contained in:
Marton Balint 2022-07-07 21:43:20 +02:00
parent 68fdc9de84
commit a6f0e641bc
1 changed files with 4 additions and 14 deletions
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18
libavfilter/vf_zscale.c
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@ -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;