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avcodec/movtextdec: Fix immediately adjacent styles 

The checks for whether a style should be opened/closed at the current
character position are as follows: A variable entry contained the index
of the currently active or potentially next active style. If the current
character position coincided with the start of style[entry], the style
was activated; this was followed by a check whether the current
character position coincided with the end of style[entry]; if so, the
style was deactivated and entry incremented. Afterwards the char was
processed.

The order of the checks leads to problems in case the endChar of style A
coincides with the startChar of the next style (say B): Style B was never
opened. When we are at said common position, the currently active style
is A and so the start pos check does not succeed; but the end pos check
does and it closes the currently active style A and increments entry.
At the next iteration of the loop, the current character position is
bigger than the start position of style B (which is style[entry]) and
therefore the style is not activated.

The solution is of course to first check for whether a style needs to be
closed (and increment entry if it does) before checking whether the next
style needs to be opened.

Reviewed-by: Philip Langdale <philipl@overt.org>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
This commit is contained in:
Andreas Rheinhardt 2020-10-17 18:42:54 +02:00
parent 40c16907bb
commit dd80066c97
1 changed files with 10 additions and 9 deletions
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19
libavcodec/movtextdec.c
View File

@ -373,7 +373,16 @@ static int text_to_ass(AVBPrint *buf, const char *text, const char *text_end,
if ((m->box_flags & STYL_BOX) && entry < m->style_entries) {
const StyleBox *style = &m->s[entry];
if (text_pos == style->style_start) {
if (text_pos == style->style_end) {
if (style_active) {
av_bprintf(buf, "{\\r}");
style_active = 0;
color = m->d.color;
}
entry++;
style++;
}
if (entry < m->style_entries && text_pos == style->style_start) {
style_active = 1;
if (style->bold ^ m->d.bold)
av_bprintf(buf, "{\\b%d}", style->bold);
@ -395,14 +404,6 @@ static int text_to_ass(AVBPrint *buf, const char *text, const char *text_end,
if (m->d.alpha != style->alpha)
av_bprintf(buf, "{\\1a&H%02X&}", 255 - style->alpha);
}
if (text_pos == style->style_end) {
if (style_active) {
av_bprintf(buf, "{\\r}");
style_active = 0;
color = m->d.color;
}
entry++;
}
}
if (m->box_flags & HLIT_BOX) {
if (text_pos == m->h.hlit_start) {