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commit 0e7427498cb1131671f6fe9d054245ae7e5a36f5
Author: popcornmix <popcornmix@gmail.com>
Date: Tue Mar 25 19:43:07 2014 +0000
[ffmpeg] Speed up wtv index creation
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
diff --git a/libavformat/wtvdec.c b/libavformat/wtvdec.c
index e423370..70898bd 100644
--- a/libavformat/wtvdec.c
+++ b/libavformat/wtvdec.c
@@ -980,21 +980,23 @@ 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;
}
}
}
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