diff options
| -rw-r--r-- | libass/ass_parse.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/libass/ass_parse.c b/libass/ass_parse.c index b40cc33..ef5c01f 100644 --- a/libass/ass_parse.c +++ b/libass/ass_parse.c @@ -603,7 +603,12 @@ char *parse_tags(ASS_Renderer *render_priv, char *p, char *end, double pwr, if (t1 == -1 && t4 == -1) { t1 = 0; t4 = render_priv->state.event->Duration; - t3 = t4 - t3; + // The value we parsed in t3 is an offset from the event end. + // What we really want in t3 is an offset from the event start. + // To this end, set t3 to (event duration - parsed value). + // If t3 >= t4, the exact value of t3 will not matter, + // so clamp it to avoid overflow in the subtraction. + t3 = t4 - FFMAX(t3, 0); } if ((render_priv->state.parsed_tags & PARSED_FADE) == 0) { render_priv->state.fade = |