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wtv: Speed up wtv index creation

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The index creation is O(N^2) with number of entries (typically thousands).
On a Pi this can take more than 60 seconds to execute for a recording of a few hours.

By replacing with an O(N) loop, this takes virtually zero time

Liked-by: Paul B Mahol <onemda@gmail.com>
Reviewed-by: Peter Ross <pross@xvid.org>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
popcornmix 2016-01-29 20:27:00 +00:00 committed by Michael Niedermayer
parent 014e4e4499
commit def56677e5
1 changed files with 10 additions and 8 deletions
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18
libavformat/wtvdec.c
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@ -1028,21 +1028,23 @@ static int read_header(AVFormatContext *s)
pb = wtvfile_open(s, root, root_size, ff_timeline_table_0_entries_Events_le16);
if (pb) {
int i;
AVIndexEntry *e = wtv->index_entries;
AVIndexEntry *e_end = wtv->index_entries + wtv->nb_index_entries - 1;
uint64_t last_position = 0;
while (1) {
uint64_t frame_nb = avio_rl64(pb);
uint64_t position = avio_rl64(pb);
while (frame_nb > e->size && e <= e_end) {
e->pos = last_position;
e++;
}
if (avio_feof(pb))
break;
for (i = wtv->nb_index_entries - 1; i >= 0; i--) {
AVIndexEntry *e = wtv->index_entries + i;
if (frame_nb > e->size)
break;
if (position > e->pos)
e->pos = position;
}
last_position = position;
}
e_end->pos = last_position;
wtvfile_close(pb);
st->duration = wtv->index_entries[wtv->nb_index_entries - 1].timestamp;
st->duration = e_end->timestamp;
}
}
}