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demux_mkv: don't add too many subtitle packets during seeking

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In insane files with a very huge number of subtitle events, and if the
--demuxer-mkv-subtitle-preroll option is given, seeking can still
overflow the packet queue. Normally, the subtitle_preroll variable
specifies the maximum number of packets that can be added. But once this
number is reached, the normal seeking behavior is enabled, which will
add all subtitle packets with the right timestamps to the packet queue.
At this point the next video keyframe can still be quite far away, with
enough subtitle packets on the way to overflow the packet queue.

Fix this by always setting an upper limit of subtitle packets read
during seeking. This should provide additional robustness even if the
preroll option is not used.

This means that even with normal seeking, at most 500 subtitle packets
are demuxed. Packets after that are discarded.

One slightly questionable aspect of this commit is that subtitle_preroll
is never reset in audio-only mode, but that is probably ok.
This commit is contained in:
wm4 2013-09-16 00:20:19 +02:00
parent 4f400d2b85
commit 4a3ceac2b5
1 changed files with 19 additions and 14 deletions
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33
demux/demux_mkv.c
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@ -197,7 +197,8 @@ typedef struct mkv_demuxer {
#define RAPROPERTIES5_SIZE 70
// Maximum number of subtitle packets that are accepted for pre-roll.
#define NUM_SUB_PREROLL_PACKETS 100
// (Subtitle packets added before first A/V keyframe packet is found with seek.)
#define NUM_SUB_PREROLL_PACKETS 500
/**
* \brief ensures there is space for at least one additional element
@ -2292,9 +2293,16 @@ static int handle_block(demuxer_t *demuxer, struct block_info *block_info)
if (mkv_d->v_skip_to_keyframe)
use_this_block = 0;
} else if (track->type == MATROSKA_TRACK_SUBTITLE) {
if (!use_this_block && mkv_d->subtitle_preroll) {
mkv_d->subtitle_preroll--;
if (!use_this_block && mkv_d->subtitle_preroll)
use_this_block = 1;
if (use_this_block) {
if (mkv_d->subtitle_preroll) {
mkv_d->subtitle_preroll--;
} else {
// This could overflow the demuxer queue.
if (mkv_d->a_skip_to_keyframe || mkv_d->v_skip_to_keyframe)
use_this_block = 0;
}
}
if (use_this_block) {
if (laces > 1) {
@ -2586,7 +2594,7 @@ static struct mkv_index *seek_with_cues(struct demuxer *demuxer, int seek_id,
if (index) { /* We've found an entry. */
uint64_t seek_pos = index->filepos;
if (mkv_d->subtitle_preroll) {
if (flags & SEEK_SUBPREROLL) {
uint64_t prev_target = 0;
for (int i = 0; i < mkv_d->num_indexes; i++) {
if (seek_id < 0 || mkv_d->indexes[i].tnum == seek_id) {
@ -2622,10 +2630,9 @@ static void demux_mkv_seek(demuxer_t *demuxer, float rel_seek_secs, int flags)
a_tnum = track->tnum;
}
}
mkv_d->subtitle_preroll = 0;
if ((flags & SEEK_SUBPREROLL) && st_active[STREAM_SUB] &&
st_active[STREAM_VIDEO])
mkv_d->subtitle_preroll = NUM_SUB_PREROLL_PACKETS;
mkv_d->subtitle_preroll = NUM_SUB_PREROLL_PACKETS;
if (!st_active[STREAM_SUB] || !st_active[STREAM_VIDEO])
flags &= ~SEEK_SUBPREROLL;
if (!(flags & (SEEK_BACKWARD | SEEK_FORWARD))) {
if (flags & SEEK_ABSOLUTE || rel_seek_secs < 0)
flags |= SEEK_BACKWARD;
@ -2654,14 +2661,13 @@ static void demux_mkv_seek(demuxer_t *demuxer, float rel_seek_secs, int flags)
if (!index)
stream_seek(demuxer->stream, old_pos);
if (st_active[STREAM_VIDEO])
mkv_d->v_skip_to_keyframe = 1;
mkv_d->v_skip_to_keyframe = st_active[STREAM_VIDEO];
mkv_d->a_skip_to_keyframe = st_active[STREAM_AUDIO];
if (flags & SEEK_FORWARD)
mkv_d->skip_to_timecode = target_timecode;
else
mkv_d->skip_to_timecode = index ? index->timecode * mkv_d->tc_scale
: 0;
mkv_d->a_skip_to_keyframe = 1;
demux_mkv_fill_buffer(demuxer);
} else if ((demuxer->movi_end <= 0) || !(flags & SEEK_ABSOLUTE))
@ -2697,10 +2703,9 @@ static void demux_mkv_seek(demuxer_t *demuxer, float rel_seek_secs, int flags)
mkv_d->cluster_end = 0;
stream_seek(s, index->filepos);
if (st_active[STREAM_VIDEO])
mkv_d->v_skip_to_keyframe = 1;
mkv_d->v_skip_to_keyframe = st_active[STREAM_VIDEO];
mkv_d->a_skip_to_keyframe = st_active[STREAM_AUDIO];
mkv_d->skip_to_timecode = index->timecode * mkv_d->tc_scale;
mkv_d->a_skip_to_keyframe = 1;
demux_mkv_fill_buffer(demuxer);
}