If the player is paused, switching subtitle track requires us to read
subs packets for an indefinite amount of time in order to actually
display the subtitles. The problem with this is that it puts a blocking
loop in the play thread which can be slow in cases where it takes a long
time to fetch the subtitle (e.g. over a network).
9e27b1f523 alleviates this when a pause
happens because of buffering, but it's not complete. One could encounter
this if the user pauses the video first manually and then switches the
subtitle track.
To solve this better, make it so the loop has a time out (totally
arbitrary number) so the player isn't blocked forever. If subtitles are
not fetched within that time, we flag the track and try again later in
the playloop.
This only affects two special cases: printing subtitles to the terminal
and printing subtitles on a still picture. Previously, mpv was very dumb
here and spammed this logic on every single loop. For terminal
subtitles, this isn't as big of a deal, but for the image case this is
pretty bad. The entire VO constantly redrew even when there was no need
to which can be very expensive depending on user settings.
Instead, let's rework sub_read_packets so that it also tells us whether
or not the subtitle packets update in some way in addition to telling us
whether or not to read more. Since we cache all packets thanks to the
previous commit, we can leverage this information to make a guess
whether or not the current subtitle packet is supposed to be visible on
the screen. Because the redraw now only happens when it is needed, the
mp_set_timeout_hack can be removed.
When updating subtitles while paused, mpv waits until a packet is
available. However in the case of a network stream, it is possible that
mpv will pause itself when buffering for cache reasons. This makes that
particular loop do a busy loop and can take a long time depending on
network streams. Simply just don't do the loop here if we are paused for
cache reasons. Fixes#13077.
Any track that has attached picture is also always considered an image.
Not every image is neccesarily an attached picture though. So change the
check here to capture more possible cases where we should be updating
the subtitle. With the previous commits, this fixes#12387.
The stream selection state wasn't improved. I didn't realize this messed
with caches. All in all, just not a good idea. Back to drawing board I
guess.
This reverts commit f40bbfec4f.
This replaces the previous commit and makes more sense. The internal
demux marked tracks as eager depending on their type and for subtitles
it would always lazily read them unless there happened to be no
available av stream. However, we want the sub stream to be eager if the
player is paused. The existing subtitle is still preserved on the
screen, but if the user changes tracks that's when the problem occurs.
So to handle this case, propagate the mpctx->paused down to the stream
selection logic. This modifies both demuxer_refresh_track and
demuxer_select_track to take that boolean value. A few other parts of
the player use this, but we can just assume false there (no change in
behavior from before) since they should never be related to subtitles.
The core player code is aware of its own state naturally, and can always
pass the appropriate value so go ahead and do so. When we change the
pause state, a refresh seek is done on all existing subtitle tracks to
make sure their eager state is the appropriate value (i.e. so it's not
still set to eager after a pause and a track switch). Slightly invasive
change, but it works with the existing logic instead of going around it
so ultimately it should be a better approach. We can additionally remove
the old force boolean from sub_read_packets since it is no longer
needed.
Internal subtitles were not shown when switching between tracks while
mpv was paused. The reason for this is simply because the demuxer data
isn't available yet when the track switch happens. Fixing it is
basically just retrying until the packet is actually available when the
player is paused. Fixes#8311.
29e15e6248 prefixed youtube-dl's subs url with an edl prefix to not
download them until they're selected, which is useful when there are
many sub languages. But this prefix broke the alignment of secondary
subs, which would overlap the primary subs instead of always being
placed at the top. This can be tested with
--sub-file='edl://!no_clip;!delay_open,media_type=sub;secondary_sub.srt'
When a sub is added, sub.c:reinit_sub() is called. This calls in
init_subdec() -> dec_sub.c:sub_create() -> init_decoder() ->
sd_ass:init(). Then reinit_sub() calls
sub_control(track->d_sub, SD_CTRL_SET_TOP, &(bool){!!order}) which sets
sd_ass_priv.on_top = true for secondary subs.
But for EDL subs the real sub is initialized again when in
dec_sub.c:sub_read_packets() is_new_segment() returns true and
update_segment() is called, or when sub_get_bitmaps() calls
update_segment(). update_segment() then calls init_decoder(), which
calls sd_ass:init(), so sd_ass_priv is reinitialized, and its on_top
property is left false. This commit sets it to true again.
For URLs that need to be downloaded it seems that the update_segment()
call that reinitializes sd_ass_priv is always the one in
sub_read_packets(), but with local subs sub_get_bitmaps() is usually
called earlier (though there shouldn't be a reason to use the EDL URL
for local subs), so I added the order parameter to sub_create(), rather
than adding it to all of update_segment(), sub_read_packets() and
sub_get_bitmaps().
Also removes the cast to bool in the other sub_control call, since
sub/sd_ass.c:control already casts arg to bool when cmd is
SD_CTRL_SET_TOP.
This fixes a long-standing apparent issue where mpv would display the last
frame with no subtitles at EOF. This is caused by sub rendering switching from
video timestamps to audio timestamps when the video ends, and audio streams
often running past the timestamp of the last video frame. However, authoring
tools (most notably Aegisub) don't tend to provide easy ways to add meaningful
subtitles after the end of the video, so this is rarely actually useful.
See manpage additions. This was requested, sort of. Although what has
been requested might be something completely different. So this is
speculative.
This also changes sub_get_text() to return an allocated copy, because
the buffer shit was too damn messy.
Apparently, this was a bit of a mess, which caused the bug fixed by
commit ec7f2388af. Try to improve this, and only use track selection
entries that exist.
This simply didn't set the direction flag in most situations, which
meant the timestamps used in the subtitle renderer were nonsense,
leading to invisible subtitles.
This works only for text subtitles that are cached in the ASS_Track
state. Reading new subtitles is broken because the demuxer layer has
trouble returning subtitle packets backwards, and I think for rendering
bitmap subtitles, the pruning direction would have to be adjusted. (Not
sure if reversing the timestamps before the subtitle renderer backend is
even the right thing to do. At least for sd_ass.c, it seems to make
sense, because it caches subtitles with "normal" timestamps.)
Track switching doesn't run reset_playback_state(), so a track enabled
at runtime during backward playback would lead to a messed up state.
This commit just does a bad code monkey fix to this. It feels like there
needs to be a much better way to propagate this state.
Move dec_video.c to filters/f_decoder_wrapper.c. It essentially becomes
a source filter. vd.h mostly disappears, because mp_filter takes care of
the dataflow, but its remains are in struct mp_decoder_fns.
One goal is to simplify dataflow by letting the filter framework handle
it (or more accurately, using its conventions). One result is that the
decode calls disappear from video.c, because we simply connect the
decoder wrapper and the filter chain with mp_pin_connect().
Another goal is to eventually remove the code duplication between the
audio and video paths for this. This commit prepares for this by trying
to make f_decoder_wrapper.c extensible, so it can be used for audio as
well later.
Decoder framedropping changes a bit. It doesn't seem to be worse than
before, and it's an obscure feature, so I'm content with its new state.
Some special code that was apparently meant to avoid dropping too many
frames in a row is removed, though.
I'm not sure how the source code tree should be organized. For one,
video/decode/vd_lavc.c is the only file in its directory, which is a bit
annoying.
Get rid of the old vf.c code. Replace it with a generic filtering
framework, which can potentially handle more than just --vf. At least
reimplementing --af with this code is planned.
This changes some --vf semantics (including runtime behavior and the
"vf" command). The most important ones are listed in interface-changes.
vf_convert.c is renamed to f_swscale.c. It is now an internal filter
that can not be inserted by the user manually.
f_lavfi.c is a refactor of player/lavfi.c. The latter will be removed
once --lavfi-complex is reimplemented on top of f_lavfi.c. (which is
conceptually easy, but a big mess due to the data flow changes).
The existing filters are all changed heavily. The data flow of the new
filter framework is different. Especially EOF handling changes - EOF is
now a "frame" rather than a state, and must be passed through exactly
once.
Another major thing is that all filters must support dynamic format
changes. The filter reconfig() function goes away. (This sounds complex,
but since all filters need to handle EOF draining anyway, they can use
the same code, and it removes the mess with reconfig() having to predict
the output format, which completely breaks with libavfilter anyway.)
In addition, there is no automatic format negotiation or conversion.
libavfilter's primitive and insufficient API simply doesn't allow us to
do this in a reasonable way. Instead, filters can use f_autoconvert as
sub-filter, and tell it which formats they support. This filter will in
turn add actual conversion filters, such as f_swscale, to perform
necessary format changes.
vf_vapoursynth.c uses the same basic principle of operation as before,
but with worryingly different details in data flow. Still appears to
work.
The hardware deint filters (vf_vavpp.c, vf_d3d11vpp.c, vf_vdpaupp.c) are
heavily changed. Fortunately, they all used refqueue.c, which is for
sharing the data flow logic (especially for managing future/past
surfaces and such). It turns out it can be used to factor out most of
the data flow. Some of these filters accepted software input. Instead of
having ad-hoc upload code in each filter, surface upload is now
delegated to f_autoconvert, which can use f_hwupload to perform this.
Exporting VO capabilities is still a big mess (mp_stream_info stuff).
The D3D11 code drops the redundant image formats, and all code uses the
hw_subfmt (sw_format in FFmpeg) instead. Although that too seems to be a
big mess for now.
f_async_queue is unused.
It was split at least across osd.c and sd_ass.c/sd_lavc.c. sd_lavc.c
actually ignored most of the more obscure subtitle timing things.
There's no reason for this - just move it all to dec_sub.c (mostly from
sd_ass.c, because it has some of the most complex stuff).
Now timestamps are transformed as they enter or leave dec_sub.c.
There appear to have been some subtle mismatches about how subtitle
timestamps were transformed, e.g. sd_functions.accepts_packet didn't
apply the subtitle speed to the timestamp. This patch should fix them,
although it's not clear if they caused actual misbehavior.
The semantics of SD_CTRL_SUB_STEP are slightly changed, which is the
reason for the changes in command.c and sd_lavc.c.
These files have all in common that they were fully or mostly taken from
mplayer.c. (mplayer.c was a huge file that contains almost all of the
playback core, until it was split into multiple parts.) This was
probably the hardest part to relicense, because so much code was moved
around all the time.
player/audio.c still does not compile. We'll have to redo audio
filtering. Once that is done, we can probably actually provide an
actual LGPL configure switch.
Here is a relatively detailed list of potential issues:
8d190244: author did not reply, parts were made GPL-only in a previous
commit.
7882ea9b: author could not be reached, but the code is gone. wscript
still has --datadir switch, but I don't think this is relevant to
copyright.
f197efd5: unclear origin, but I consider the code gone anyway (replaced
with generic OSD mechanisms).
8337d9c2: author did not reply, but only the option still exists (under
a different name), other code was removed.
d8fd7131: did not reply. Disabled in a previous commit.
05258251: same author as above. Both fields actually seem to have
vanished (even when tracking renames), so no action taken.
d459e644, 268b2c1a: author did not reply, but we reuse only the options
(with different names and slightly or fully different semantics, and
completely different implementations), so I don't think this is relevant
for copyright.
09e742fe, 17c39c4e: same as above.
e8a173de, bff4b3ee: author could not be reached. The commands were
reworked to properties, and the code outside of the TV code were moved
back to the TV code. So I don't think copyright applies to the current
command.c parts (mp_property_tv_color, mp_property_tv_freq,
mp_property_tv_scan). The TV parts remain GPL.
0810e427: could not be reached. Disabled in a previous commit.
43744a2d: unknown author, but this was replaced by dynamic alloc (if the
change is even copyrightable).
116ca0c7: unknown author; reasoning see input.c relicensing commit.
e7e4d1d8: these semantics still exist, but as generic code, and this
code was fully removed.
f1175cd9: the author of the cited patch is unknown, and upon inspection
it turns out that I was only using the idea to pause the player on EOF,
so I claim it's not copyright relevant.
25affdcc: author could not be reached (yet) - but it's only a function
rename, not copyrightable.
5728504c was committed by Arpi (who agreed), but hints that it might be
by a different author. In fact it seems to be mostly this patch:
http://lists.mplayerhq.hu/pipermail/mplayer-dev-eng/2001-November/002041.html
The author did not respond, but it all seems to have been removed later.
It's a terrible mess though. Arpi reverted the A-V sync code at first,
but left the RTC code for a while. The following commits remove these
changes 100%: 14b35442, 7181a091, 31482783, 614f8475, df58e822.
cehoyos did explicitly not agree to LGPL, but was involved in the
following changes:
c99d8fc8: applied a patch and didn't modify it, the original author
agreed.
40ac0d31: author could not be reached, but all code is gone anyway. The
"af" command has a similar function, but works completely different and
actually reuses a mechanism older than this patch.
54350436: applied a patch, but didn't modify it, except for adding a
German translation, which was removed later.
a2dda036: same situation as above
240b743e: this was made GPL-only in a previous commit
7b25afd7: same as above (for now)
kirijua could not be reached, but was a regular patch contributor:
c2c997fd: video equalizer code move; probably not copyrightable. Is GPL
due to Nick anyway.
be54f481: technically, this became the audio track property later. But
all what is left is the fact that you pass a track ID to it, so consider
the original coypright non-relevant.
2f376d1b: this was rewritten in b7052b43, but for now we can afford to
be careful, so this was marked as GPL only in a previous commit.
43844d09: remaining parts in main.c were reverted in a previous commit.
anders has mostly disagreed with the LGPL relicensing. Does not want
libaf to become LGPL, but made some concessions. In particular, he
granted us permission to relicense 4943e9c52c and 242aa6ebd4. We also
consider some of his changes remaining in mpv not relevant for copyright
(such as 735de602 - we won't remove the this option completely). We will
completely remove his other contributions, including the entire audio
filter chain. For now, this stuff is marked as GPL only. The remaining
question is how much code in player/audio.c (based on the former
mplayer.c and dec_audio.c) is under his copyright. I made claims about
this in a previous commit.
Nick(ols) Kurshev, svn username "nick" and "nickols_k", could not be
reached. He had a lot of changes in early MPlayer. It seems all of that
was removed, at least in mpv. His main work, like VIDIX or libswscale
work, does not exist in mpv anymore, but the changes to mplayer.c and
other core parts still deserve attention:
a4119f6b, fb927549, ad3529b8, e11b23dc, 5f2178be, 93c371d5: removed in
b43d67e0, d1628d12, 24ed01fe, df58e822.
0a83c6ec, 104c125e, 4e067f62, aec5dcc8, b587a3d6, f3de6e6b: DR, VAA, and
"tune" stuff was fully removed later on or replaced with other
mechanisms.
340183b0: screenshots were redone later (the VOCTRL was even removed,
with an independent implementation using the same VOCTRL a few years
later), so not relevant anymore. Basically only the 's' shortcut remains
(but not its implementation).
92c5c274, bffd4007, 555c6766: for now marked as GPL only in a previous
commit.
Might contain some trace amounts of "michael"'s copyright, who agreed to
LGPL only once the core is relicensed. This will still be respected, but
I don't think it matters at this in this case. (Some code touched by him
was merged into mplayer.c, and then disappeared after heavy
refactoring.)
I tried to be as careful and as complete as possible. It can't be
excluded that amends to this will be made later.
This does not make the player LGPL yet.
Coverart mode has the same issue as no-video mode, except that the video
chain is fully active. It shows only 1 frame at the start, which would
normally mean that only the subtitle at timestamp 0 is shown. Use the
no-video subtitle rendering mode in this case instead.
(This still doesn't handle subtitle display when playing cover-art
without audio, or playing a single image. This is because there's
nothing that will advance playback_pts.)
This code would just keep it busy while e.g. being paused. Even if it's
not paused, it couldn't help with anything since we obviously still lock
display to the externally updated PTS.
If a VO is created, but no video is playing (i.e. --force-window is
used), then until now no subtitles were shown. This is because VO
subtitle display normally depends on video frame timing. If there are no
video frames, there can be no subtitles.
Change this and add some code to handle this situation specifically. Set
a subtitle PTS manually and request VO redrawing manually, which gets
the subtitles rendered somehow.
This is kind of shaky. The subtitles are essentially sampled at
arbitrary times (such as when new audio data is decoded and pushed to
the AO, or on user interaction). To make a it slightly more consistent,
force a completely arbitrary minimum FPS of 10.
Other solutions (such as creating fake video) would be more intrusive or
would require VO-level API changes.
Fixes#3684.
When switching a subtitle track, the subtitle wasn't necessarily
updated, especially when playback was paused.
Some awfully subtle and complex interactions here.
First off (and not so subtle), the subtitle decoder will read packets
only on explicit update_subtitles() calls, which, if video is active, is
called only when a new video frame is shown. (A simply video frame
redraw doesn't trigger this.) So call it explicitly. But only if
playback is "initialized", i.e. not when it does initial track selection
and decoder init, during which no packets should be read.
The second issue is that the demuxer thread simply will not read new
packets just because a track was switched, especially if playback is
paused. That's fine, but if a refresh seek is to be done, it really
should do this. So if there's either 1. a refresh seek requested, or 2.
a refresh seek ongoing, then read more packets.
Note that it's entirely possible that we overflow the packet queue with
this in unpredicated weird corner cases, but the queue limit will still
be enforced, so this shouldn't make the situation worse.
No need to have them everywhere. The only exception/annoyance is
MAX_OSD_PARTS, which is now basically duplicated (and at runtime
initialization is checked with an assert()).
Subtitles can be preloaded, which means they're fully read and copied
into ASS_Track. This in turn is mainly for the sake of being able to do
subtitle seeking (when it comes down to it, subtitle seeking is the
cause for most trouble here).
Commit a714f8e92 broke preloaded subtitles which have events with
unknown duration, such as some MicroDVD samples. The event list gets
cleared on every seek, so the property of being preloaded obviously gets
lost.
Fix this by moving most of the preloading logic to dec_sub.c. If the
subtitle list gets cleared, they are not considered preloaded anymore,
and the logic for demuxed subtitles is used.
As another minor thing, preloadeding subtitles did neither disable the
demux stream, nor did it discard packets. Thus you could get queue
overflows in theory (harmless, but annoying). Fix this by explicitly
discarding packets in preloaded mode.
In summary, now the only difference between preloaded and normal
demuxing are:
1. a seek is issued, and all packets are read on start
2. during playback, discard the packets instead of feeding them to the
subtitle decoder
This is still petty annoying. It would be nice if maintaining the
subtitle index (and maybe a subtitle packet cache for instant subtitle
presentation when seeking back) could be maintained in the demuxer
instead. Half of all file formats with interleaved subtitles have
this anyway (mp4, mkv muxed with newer mkvmerge).
Commit 8d4a179c made subtitle decoders pick up fonts strictly from the
same source file (i.e. the same demuxer).
It breaks some fucked up use-case, and 2 people on this earth complained
about the change because of this. Add it back.
This copies all attached fonts on each subtitle init. I considered
converting attachments to use refcounting, but it'd probably be much
more complex.
Since it's slightly harder to get a list of active demuxers with
duplicate removed, the prev_demuxer variable serves as a hack to achieve
almost the same thing, except in weird corner cases. (In which fonts
could be added twice.)
Ever since a change in mplayer2 or so, relative seeks were translated to
absolute seeks before sending them to the demuxer in most cases. The
only exception in current mpv is DVD seeking.
Remove the SEEK_ABSOLUTE flag; it's not the implied default. SEEK_FACTOR
is kept, because it's sometimes slightly useful for seeking in things
like transport streams. (And maybe mkv files without duration set?)
DVD seeking is terrible because DVD and libdvdnav are terrible, but
mostly because libdvdnav is terrible. libdvdnav does not expose seeking
with seek tables. (Although I know xbmc/kodi use an undocumented API
that is not declared in the headers by dladdr()ing it - I think the
function is dvdnav_jump_to_sector_by_time().) With the current mpv
policy if not giving a shit about DVD, just revert our half-working seek
hacks and always use dvdnav_time_search(). Relative seeking might get
stuck sometimes; in this case --hr-seek=always is recommended.
Most text subtitles are read completely on loading (libavformat works
this way, and there are good reasons to do it on the higher levels too).
This leads to some messy problems. For example, the subtitle path is the
only one which might read packets during decoder initialization. This is
not neccessary; get rid of it.
This fixes a potential problem of seeking to position 0 for image
subtitles on init, and if the start position is not at the beginning of
the timeline.
Eventually we want the VO be driven by a A->V filter, so a decoder
doesn't even have to exist. Some features definitely require a decoder
though (like reporting the decoder in use, hardware decoding, etc.), so
for each thing which accessed d_video, it has to be redecided if and how
it can access decoder state.
At least the "framedrop" property slightly changes semantics: you can
now always set this property, even if no video is active.
Some untested changes in this commit, but our bio-based distributed
test suite has to take care of this.
Lots of noise to remove the vfilter/vo fields from dec_video.
From now on, video filtering and output will still be done together,
summarized under struct vo_chain.
There is the question where exactly the vf_chain should go in such a
decoupled architecture. The end goal is being able to place a "complex"
filter between video decoders and output (which will culminate in
natural integration of A->V filters for natural integration of
libavfilter audio visualizations). The vf_chain is still useful for
"final" processing, such as format conversions and deinterlacing. Also,
there's only 1 VO and 1 --vf option. So having 1 vf_chain for a VO seems
ideal, since otherwise there would be no natural way to handle all these
existing options and mechanisms.
There is still some work required to truly decouple decoding.
Instead of handling this on filter chain reinit, do it directly after
the decoder. This makes the code less entangled. In particular, this
gets rid of the really weird "override params" concept in the video
filter code.
The last_format/fixed_formats have some redundance with decoder_output,
but unfortunately the latter has a slightly different use.
This is mainly a refactor. I'm hoping it will make some things easier
in the future due to cleanly separating codec metadata and stream
metadata.
Also, declare that the "codec" field can not be NULL anymore. demux.c
will set it to "" if it's NULL when added. This gets rid of a corner
case everything had to handle, but which rarely happened.
Slightly change how it is decided when a new packet should be read.
Switch to demux_read_packet_async(), and let the player "wait properly"
until required subtitle packets arrive, instead of blocking everything.
Move distinguishing the cases of passive and active reading into the
demuxer, where it belongs.
Just simplify by removing parts not needed anymore. This includes
merging dec_sub allocation and initialization (since things making
initialization complicated were removed), or format support queries (it
simply tries to create a decoder, and if that fails, tries the next
one).
So that the video FPs is not required at initialization, and can be set
later.
(As for whether this MicroDVD crap is worth the trouble to handle it
"correctly": MicroDVD files are unfortunately still around, and in at
least one case using the video FPS seemed to help indeed.)
Keeping ASS_Renderers around for a potentially large number of subtitle
tracks could lead to excessive memory usage, especially since the libass
cache is broken (caches even unneeded data), and might consume up to
~500MB of memory for no reason.
This includes the case of switching ordered chapter boundaries. It will
now be recreated on each timeline part switch. This shouldn't be much of
a problem with modern libass. (Older libass versions use fontconfig for
memory fonts, and will be very slow to reinitialize memory fonts.)
Since commit 6d9cb893, subtitle state doesn't survive timeline switches
(ordered chapters etc.). So there is no point in caching the state per
sh_stream anymore (which would be required to deal with multiple
segments). Move the cache to struct track.
(Whether it's worth caching the subtitle state just for the situation
when subtitle tracks get reselected is questionable. But for now, it's
nice to have the subtitles immediately show up when reselecting a
subtitle.)
The demuxer infrastructure was originally single-threaded. To make it
suitable for multithreading (specifically, demuxing and decoding on
separate threads), some sort of tripple-buffering was introduced. There
are separate "struct demuxer" allocations. The demuxer thread sets the
state on d_thread. If anything changes, the state is copied to d_buffer
(the copy is protected by a lock), and the decoder thread is notified.
Then the decoder thread copies the state from d_buffer to d_user (again
while holding a lock). This avoids the need for locking in the
demuxer/decoder code itself (only demux.c needs an internal, "invisible"
lock.)
Remove the streams/num_streams fields from this tripple-buffering
schema. Move them to the internal struct, and protect them with the
internal lock. Use accessors for read access outside of demux.c.
Other than replacing all field accesses with accessors, this separates
allocating and adding sh_streams. This is needed to avoid race
conditions. Before this change, this was awkwardly handled by first
initializing the sh_stream, and then sending a stream change event. Now
the stream is allocated, then initialized, and then declared as
immutable and added (at which point it becomes visible to the decoder
thread immediately).
This change is useful for PR #2626. And eventually, we should probably
get entirely of the tripple buffering, and this makes a nice first step.
Apparently, this was replaced by the SD_CTRL_SET_VIDEO_PARAMS set
dimensions. But I can't find out when this happened - possibly, these
fields were never used by sd_lavc.c, and only by the (long removed)
MPlayer dvdsub decoder.
Until now, feeding packets to the decoder in advance was done for text
subtitles only. This was possible because libass buffers all subtitle
data anyway (in ASS_Track). sd_lavc, responsible for bitmap subs, does
not do this. But it can buffer a small number of subtitle frames ahead.
Enable this.
Repurpose the sub_accept_packets_in_advance(). Instead of "can take all
packets" it means "can take 1 packet" now. (The old meaning is still
needed locally in dec_sub.c; keep it there.) It asks the decoder whether
there is place for at least 1 subtitle packet. sd_lavc implements it and
returns true if its internal fixed-size subtitle queue still has a free
slot. (The implementation of this in dec_sub.c isn't entirely clean.
For one, decode_chain() ignores this mechanism, so it's implied that
bitmap subtitles do not use the subtitle filter chain in any advanced
way.)
Also fix 2 bugs in the sd_lavc queue handling. Subtitles must be checked
in reverse, because the first entry will often have endpts==NOPTS, which
would always match. alloc_sub() must cycle the queue buffer, because it
reuses memory allocations (like sub.imgs) by design.
This was used with --no-sub-ass (aka --no-ass). This option (which is
not yet removed) strips all styling from the subtitles, and renders them
as plaintext only. For some reason, it originally seemed convenient to
reuse all the OSD text rendering code (osd_libass.c). While this was
indeed simple, it had a bad influence on the rest of the code. For
example, it had to decide whether to go through the OSD code path, or
the proper subtitle renderer in sd_ass.c.
Kill the OSD subtitle renderer. Reimplement --no-sub-ass and also
"secondary" subtitles in sd_ass.c. fill_plaintext() contains some rather
minor code duplication with osd_libass.c for setting up a dummy
ASS_Event and escaping the stripped text. Since sd_ass.c already has to
handle "normal" text subtitles, and has code for stripping ASS tags,
this remains all relatively simple.
Remove all the unnecessary crap from the rest of the code.
Use the demux_set_ts_offset() added in the previous commit to base each
timeline segment to use timestamps according to its relative position
within the overall timeline. As a consequence we don't need to care
about these timestamps anymore, and everything becomes simpler.
(Another minor but delicious nugget of sanity.)
