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sub: adjust offsets when sub seeking/stepping

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In the sub seek code path, there was an arbitrary small offset added to
the pts before the seek. However when seeking backwards, the offset was
an additional subtraction. de6eace6e9
added this logic 10 years ago and perhaps it made sense then, but the
additional subtraction when seeking backwards causes the subtitle seek
to go too far to the previous subtitle if the durations overlap. This
should always be an addition to work correctly. Additionally, the sub
stepping code path also could use this offset for the same reason
(duration overlaps). However, it is only applicable to sd_ass not
sd_lavc. sd_lavc has step_sub support but on a sample it didn't even
work anyway. Perhaps it only works for certain kinds of subtitles
(patches welcome).

Anyways instead of keeping this offset as a magic number, we can define
it in sd.h which is handy for this. For sd_ass, we add the offset when
sub stepping, and the offset is always added for sub seeking like it was
before. Update the comment to be a little more relevant to what actually
happens today. Fixes #11445.
This commit is contained in:
Dudemanguy 2023-11-05 19:29:18 -06:00
parent 7d004bf15c
commit 953176ee42
3 changed files with 10 additions and 7 deletions
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12
player/command.c
View File

@ -49,8 +49,9 @@
#include "demux/demux.h"
#include "demux/stheader.h"
#include "common/playlist.h"
#include "sub/osd.h"
#include "sub/dec_sub.h"
#include "sub/osd.h"
#include "sub/sd.h"
#include "options/m_option.h"
#include "options/m_property.h"
#include "options/m_config_frontend.h"
@ -5410,11 +5411,10 @@ static void cmd_sub_step_seek(void *p)
&mpctx->opts->subs_rend->sub_delay);
show_property_osd(mpctx, "sub-delay", cmd->on_osd);
} else {
// We can easily get stuck by failing to seek to the video
// frame which actually shows the sub first (because video
// frame PTS and sub PTS rarely match exactly). Add some
// rounding for the mess of it.
a[0] += 0.01 * (a[1] >= 0 ? 1 : -1);
// We can easily seek/step to the wrong subtitle line (because
// video frame PTS and sub PTS rarely match exactly). Add an
// arbitrary forward offset as a workaround.
a[0] += SUB_SEEK_OFFSET;
mark_seek(mpctx);
queue_seek(mpctx, MPSEEK_ABSOLUTE, a[0], MPSEEK_EXACT,
MPSEEK_FLAG_DELAY);

2
sub/sd.h
View File

@ -9,6 +9,8 @@
#define SUB_GAP_THRESHOLD 0.210
// don't change timings if durations are smaller
#define SUB_GAP_KEEP 0.4
// slight offset when sub seeking or sub stepping
#define SUB_SEEK_OFFSET 0.01
struct sd {
struct mpv_global *global;

3
sub/sd_ass.c
View File

@ -844,7 +844,8 @@ static int control(struct sd *sd, enum sd_ctrl cmd, void *arg)
long long res = ass_step_sub(ctx->ass_track, ts, a[1]);
if (!res)
return false;
a[0] += res / 1000.0;
// Try to account for overlapping durations
a[0] += res / 1000.0 + SUB_SEEK_OFFSET;
return true;
}
case SD_CTRL_SET_VIDEO_PARAMS: