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avformat/matroskadec: Improve check for level 1 duplicates

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If a file uses unknown-length level 1 elements besides clusters and such
elements are after the first cluster, then these elements will usually
be parsed twice: Once during parsing of the file header and once when
reading the file reaches the position where these elements are located.
The second time the element is parsed leads to a "Duplicate element"
error message. Known-length elements are not affected by this as they
are skipped except during parsing the header.

This commit fixes this by explicitly adding a check for whether the
position of the element to be parsed is the same as the position of the
already known level 1 element.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
This commit is contained in:
Andreas Rheinhardt 2019-05-17 00:30:21 +02:00 committed by James Almer
parent 730ac1ae80
commit 806ac7da69
1 changed files with 4 additions and 1 deletions
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5
libavformat/matroskadec.c
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@ -1390,7 +1390,10 @@ static int ebml_parse(MatroskaDemuxContext *matroska,
matroska->cues_parsing_deferred = 0;
if (syntax->type == EBML_LEVEL1 &&
(level1_elem = matroska_find_level1_elem(matroska, syntax->id))) {
if (level1_elem->parsed)
if (!level1_elem->pos) {
// Zero is not a valid position for a level 1 element.
level1_elem->pos = pos;
} else if (level1_elem->pos != pos)
av_log(matroska->ctx, AV_LOG_ERROR, "Duplicate element\n");
level1_elem->parsed = 1;
}