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mpv/sub/dec_sub.c
wm4 4a8647b6b8 sub: don't potentially discard too many subtitles on seek
The accepts_packet packet callback is supposed to deal with subtitle
decoders which have only a small queue of current subtitle events (i.e.
sd_lavc.c), in case feeding it too many packets would discard events
that are still needed.

Normally, the number of subtitles that need to be preserved is estimated
by the rendering pts (get_bitmaps() argument). Rendering lags behind
decoding, so normally the rendering pts is smaller than the next video
frame pts, and we simply discard all subtitle events until the rendering
pts.

This breaks down in some annoying corner cases. One of them is seeking
backwards: the VO will still try to render the old PTS during seeks,
which passes a high PTS to the subtitle renderer, which in turn would
discard more subtitles than it should. There is a similar issue with
forward seeks. Add hacks to deal with those issues.

There should be a better way to deal with the essentially unknown
"rendering position", which is made worse by screenshots or rendering
with vf_sub. At the very least, we could handle seeks better, and e.g.
either force the VO not to re-render subs after seeks (ugly), or
introduce seek sequence numbers to distinguish attempts to render
earlier subtitles when a seek is done.
2016-08-14 20:27:37 +02:00

321 lines
9.0 KiB
C

/*
* This file is part of mpv.
*
* mpv is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* mpv is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with mpv. If not, see <http://www.gnu.org/licenses/>.
*/
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <math.h>
#include <assert.h>
#include <pthread.h>
#include "config.h"
#include "demux/demux.h"
#include "sd.h"
#include "dec_sub.h"
#include "options/options.h"
#include "common/global.h"
#include "common/msg.h"
#include "osdep/threads.h"
extern const struct sd_functions sd_ass;
extern const struct sd_functions sd_lavc;
static const struct sd_functions *const sd_list[] = {
&sd_lavc,
#if HAVE_LIBASS
&sd_ass,
#endif
NULL
};
struct dec_sub {
pthread_mutex_t lock;
struct mp_log *log;
struct mpv_global *global;
struct MPOpts *opts;
struct attachment_list *attachments;
struct sh_stream *sh;
double last_pkt_pts;
bool preload_attempted;
struct mp_codec_params *codec;
double start, end;
double last_vo_pts;
struct sd *sd;
struct demux_packet *new_segment;
};
void sub_lock(struct dec_sub *sub)
{
pthread_mutex_lock(&sub->lock);
}
void sub_unlock(struct dec_sub *sub)
{
pthread_mutex_unlock(&sub->lock);
}
void sub_destroy(struct dec_sub *sub)
{
if (!sub)
return;
sub_reset(sub);
sub->sd->driver->uninit(sub->sd);
talloc_free(sub->sd);
pthread_mutex_destroy(&sub->lock);
talloc_free(sub);
}
static struct sd *init_decoder(struct dec_sub *sub)
{
for (int n = 0; sd_list[n]; n++) {
const struct sd_functions *driver = sd_list[n];
struct sd *sd = talloc(NULL, struct sd);
*sd = (struct sd){
.global = sub->global,
.log = mp_log_new(sd, sub->log, driver->name),
.opts = sub->opts,
.driver = driver,
.attachments = sub->attachments,
.codec = sub->codec,
.preload_ok = true,
};
if (sd->driver->init(sd) >= 0)
return sd;
talloc_free(sd);
}
MP_ERR(sub, "Could not find subtitle decoder for format '%s'.\n",
sub->codec->codec);
return NULL;
}
// Thread-safety of the returned object: all functions are thread-safe,
// except sub_get_bitmaps() and sub_get_text(). Decoder backends (sd_*)
// do not need to acquire locks.
// Ownership of attachments goes to the caller, and is released with
// talloc_free() (even on failure).
struct dec_sub *sub_create(struct mpv_global *global, struct sh_stream *sh,
struct attachment_list *attachments)
{
assert(sh && sh->type == STREAM_SUB);
struct dec_sub *sub = talloc(NULL, struct dec_sub);
*sub = (struct dec_sub){
.log = mp_log_new(sub, global->log, "sub"),
.global = global,
.opts = global->opts,
.sh = sh,
.codec = sh->codec,
.attachments = talloc_steal(sub, attachments),
.last_pkt_pts = MP_NOPTS_VALUE,
.last_vo_pts = MP_NOPTS_VALUE,
.start = MP_NOPTS_VALUE,
.end = MP_NOPTS_VALUE,
};
mpthread_mutex_init_recursive(&sub->lock);
sub->sd = init_decoder(sub);
if (sub->sd)
return sub;
talloc_free(sub);
return NULL;
}
// Called locked.
static void update_segment(struct dec_sub *sub)
{
if (sub->new_segment && sub->last_vo_pts != MP_NOPTS_VALUE &&
sub->last_vo_pts >= sub->new_segment->start)
{
MP_VERBOSE(sub, "Switch segment: %f at %f\n", sub->new_segment->start,
sub->last_vo_pts);
sub->codec = sub->new_segment->codec;
sub->start = sub->new_segment->start;
sub->end = sub->new_segment->end;
struct sd *new = init_decoder(sub);
if (new) {
sub->sd->driver->uninit(sub->sd);
talloc_free(sub->sd);
sub->sd = new;
} else {
// We'll just keep the current decoder, and feed it possibly
// invalid data (not our fault if it crashes or something).
MP_ERR(sub, "Can't change to new codec.\n");
}
sub->sd->driver->decode(sub->sd, sub->new_segment);
talloc_free(sub->new_segment);
sub->new_segment = NULL;
}
}
bool sub_can_preload(struct dec_sub *sub)
{
bool r;
pthread_mutex_lock(&sub->lock);
r = sub->sd->driver->accept_packets_in_advance && !sub->preload_attempted;
pthread_mutex_unlock(&sub->lock);
return r;
}
void sub_preload(struct dec_sub *sub)
{
pthread_mutex_lock(&sub->lock);
sub->preload_attempted = true;
for (;;) {
struct demux_packet *pkt = demux_read_packet(sub->sh);
if (!pkt)
break;
sub->sd->driver->decode(sub->sd, pkt);
talloc_free(pkt);
}
pthread_mutex_unlock(&sub->lock);
}
// Read packets from the demuxer stream passed to sub_create(). Return true if
// enough packets were read, false if the player should wait until the demuxer
// signals new packets available (and then should retry).
bool sub_read_packets(struct dec_sub *sub, double video_pts)
{
bool r = true;
pthread_mutex_lock(&sub->lock);
while (1) {
bool read_more = true;
if (sub->sd->driver->accepts_packet)
read_more = sub->sd->driver->accepts_packet(sub->sd, video_pts);
if (!read_more)
break;
if (sub->new_segment && sub->new_segment->start < video_pts) {
sub->last_vo_pts = video_pts;
update_segment(sub);
}
if (sub->new_segment)
break;
struct demux_packet *pkt;
int st = demux_read_packet_async(sub->sh, &pkt);
// Note: "wait" (st==0) happens with non-interleaved streams only, and
// then we should stop the playloop until a new enough packet has been
// seen (or the subtitle decoder's queue is full). This does not happen
// for interleaved subtitle streams, which never return "wait" when
// reading.
if (st <= 0) {
r = st < 0 || (sub->last_pkt_pts != MP_NOPTS_VALUE &&
sub->last_pkt_pts > video_pts);
break;
}
sub->last_pkt_pts = pkt->pts;
if (pkt->new_segment) {
sub->new_segment = pkt;
// Note that this can be delayed to a much later point in time.
update_segment(sub);
break;
}
if (!(sub->preload_attempted && sub->sd->preload_ok))
sub->sd->driver->decode(sub->sd, pkt);
talloc_free(pkt);
}
pthread_mutex_unlock(&sub->lock);
return r;
}
// You must call sub_lock/sub_unlock if more than 1 thread access sub.
// The issue is that *res will contain decoder allocated data, which might
// be deallocated on the next decoder access.
void sub_get_bitmaps(struct dec_sub *sub, struct mp_osd_res dim, int format,
double pts, struct sub_bitmaps *res)
{
struct MPOpts *opts = sub->opts;
sub->last_vo_pts = pts;
update_segment(sub);
if (sub->end != MP_NOPTS_VALUE && pts >= sub->end)
return;
if (opts->sub_visibility && sub->sd->driver->get_bitmaps)
sub->sd->driver->get_bitmaps(sub->sd, dim, format, pts, res);
}
// See sub_get_bitmaps() for locking requirements.
// It can be called unlocked too, but then only 1 thread must call this function
// at a time (unless exclusive access is guaranteed).
char *sub_get_text(struct dec_sub *sub, double pts)
{
pthread_mutex_lock(&sub->lock);
struct MPOpts *opts = sub->opts;
char *text = NULL;
sub->last_vo_pts = pts;
update_segment(sub);
if (opts->sub_visibility && sub->sd->driver->get_text)
text = sub->sd->driver->get_text(sub->sd, pts);
pthread_mutex_unlock(&sub->lock);
return text;
}
void sub_reset(struct dec_sub *sub)
{
pthread_mutex_lock(&sub->lock);
if (sub->sd->driver->reset)
sub->sd->driver->reset(sub->sd);
sub->last_pkt_pts = MP_NOPTS_VALUE;
sub->start = sub->end = MP_NOPTS_VALUE;
sub->last_vo_pts = MP_NOPTS_VALUE;
talloc_free(sub->new_segment);
sub->new_segment = NULL;
pthread_mutex_unlock(&sub->lock);
}
void sub_select(struct dec_sub *sub, bool selected)
{
pthread_mutex_lock(&sub->lock);
if (sub->sd->driver->select)
sub->sd->driver->select(sub->sd, selected);
pthread_mutex_unlock(&sub->lock);
}
int sub_control(struct dec_sub *sub, enum sd_ctrl cmd, void *arg)
{
int r = CONTROL_UNKNOWN;
pthread_mutex_lock(&sub->lock);
if (sub->sd->driver->control)
r = sub->sd->driver->control(sub->sd, cmd, arg);
pthread_mutex_unlock(&sub->lock);
return r;
}