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https://github.com/mpv-player/mpv
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b9d351f02a
See manpage additions. This is a huge hack. You can bet there are shit
tons of bugs. It's literally forcing square pegs into round holes.
Hopefully, the manpage wall of text makes it clear enough that the whole
shit can easily crash and burn. (Although it shouldn't literally crash.
That would be a bug. It possibly _could_ start a fire by entering some
sort of endless loop, not a literal one, just something where it tries
to do work without making progress.)
(Some obvious bugs I simply ignored for this initial version, but
there's a number of potential bugs I can't even imagine. Normal playback
should remain completely unaffected, though.)
How this works is also described in the manpage. Basically, we demux in
reverse, then we decode in reverse, then we render in reverse.
The decoding part is the simplest: just reorder the decoder output. This
weirdly integrates with the timeline/ordered chapter code, which also
has special requirements on feeding the packets to the decoder in a
non-straightforward way (it doesn't conflict, although a bugmessmass
breaks correct slicing of segments, so EDL/ordered chapter playback is
broken in backward direction).
Backward demuxing is pretty involved. In theory, it could be much
easier: simply iterating the usual demuxer output backward. But this
just doesn't fit into our code, so there's a cthulhu nightmare of shit.
To be specific, each stream (audio, video) is reversed separately. At
least this means we can do backward playback within cached content (for
example, you could play backwards in a live stream; on that note, it
disables prefetching, which would lead to losing new live video, but
this could be avoided).
The fuckmess also meant that I didn't bother trying to support
subtitles. Subtitles are a problem because they're "sparse" streams.
They need to be "passively" demuxed: you don't try to read a subtitle
packet, you demux audio and video, and then look whether there was a
subtitle packet. This means to get subtitles for a time range, you need
to know that you demuxed video and audio over this range, which becomes
pretty messy when you demux audio and video backwards separately.
Backward display is the most weird (and potentially buggy) part. To
avoid that we need to touch a LOT of timing code, we negate all
timestamps. The basic idea is that due to the navigation, all
comparisons and subtractions of timestamps keep working, and you don't
need to touch every single of them to "reverse" them.
E.g.:
bool before = pts_a < pts_b;
would need to be:
bool before = forward
? pts_a < pts_b
: pts_a > pts_b;
or:
bool before = pts_a * dir < pts_b * dir;
or if you, as it's implemented now, just do this after decoding:
pts_a *= dir;
pts_b *= dir;
and then in the normal timing/renderer code:
bool before = pts_a < pts_b;
Consequently, we don't need many changes in the latter code. But some
assumptions inhererently true for forward playback may have been broken
anyway. What is mainly needed is fixing places where values are passed
between positive and negative "domains". For example, seeking and
timestamp user display always uses positive timestamps. The main mess is
that it's not obvious which domain a given variable should or does use.
Well, in my tests with a single file, it suddenly started to work when I
did this. I'm honestly surprised that it did, and that I didn't have to
change a single line in the timing code past decoder (just something
minor to make external/cached text subtitles display). I committed it
immediately while avoiding thinking about it. But there really likely
are subtle problems of all sorts.
As far as I'm aware, gstreamer also supports backward playback. When I
looked at this years ago, I couldn't find a way to actually try this,
and I didn't revisit it now. Back then I also read talk slides from the
person who implemented it, and I'm not sure if and which ideas I might
have taken from it. It's possible that the timestamp reversal is
inspired by it, but I didn't check. (I think it claimed that it could
avoid large changes by changing a sign?)
VapourSynth has some sort of reverse function, which provides a backward
view on a video. The function itself is trivial to implement, as
VapourSynth aims to provide random access to video by frame numbers (so
you just request decreasing frame numbers). From what I remember, it
wasn't exactly fluid, but it worked. It's implemented by creating an
index, and seeking to the target on demand, and a bunch of caching. mpv
could use it, but it would either require using VapourSynth as demuxer
and decoder for everything, or replacing the current file every time
something is supposed to be played backwards.
FFmpeg's libavfilter has reversal filters for audio and video. These
require buffering the entire media data of the file, and don't really
fit into mpv's architecture. It could be used by playing a libavfilter
graph that also demuxes, but that's like VapourSynth but worse.
359 lines
8.3 KiB
C
359 lines
8.3 KiB
C
#ifndef MPLAYER_OPTIONS_H
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#define MPLAYER_OPTIONS_H
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#include <stdbool.h>
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#include <stdint.h>
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#include "m_option.h"
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#include "common/common.h"
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typedef struct mp_vo_opts {
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struct m_obj_settings *video_driver_list;
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int taskbar_progress;
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int snap_window;
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int ontop;
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int ontop_level;
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int fullscreen;
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int border;
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int fit_border;
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int all_workspaces;
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int screen_id;
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int fsscreen_id;
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char *winname;
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int x11_netwm;
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int x11_bypass_compositor;
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int native_keyrepeat;
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float panscan;
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float zoom;
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float pan_x, pan_y;
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float align_x, align_y;
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int unscaled;
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struct m_geometry geometry;
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struct m_geometry autofit;
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struct m_geometry autofit_larger;
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struct m_geometry autofit_smaller;
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double window_scale;
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int keepaspect;
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int keepaspect_window;
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int hidpi_window_scale;
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int native_fs;
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int64_t WinID;
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float force_monitor_aspect;
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float monitor_pixel_aspect;
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int force_window_position;
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char *mmcss_profile;
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double override_display_fps;
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double timing_offset;
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// vo_drm
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struct sws_opts *sws_opts;
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// vo_drm
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struct drm_opts *drm_opts;
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} mp_vo_opts;
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// Subtitle options needed by the subtitle decoders/renderers.
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struct mp_subtitle_opts {
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int sub_visibility;
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int sub_pos;
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float sub_delay;
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float sub_fps;
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float sub_speed;
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int forced_subs_only;
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int stretch_dvd_subs;
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int stretch_image_subs;
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int image_subs_video_res;
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int sub_fix_timing;
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int sub_scale_by_window;
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int sub_scale_with_window;
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int ass_scale_with_window;
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struct osd_style_opts *sub_style;
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float sub_scale;
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float sub_gauss;
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int sub_gray;
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int sub_filter_SDH;
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int sub_filter_SDH_harder;
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int ass_enabled;
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float ass_line_spacing;
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int ass_use_margins;
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int sub_use_margins;
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int ass_vsfilter_aspect_compat;
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int ass_vsfilter_color_compat;
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int ass_vsfilter_blur_compat;
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int use_embedded_fonts;
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char **ass_force_style_list;
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char *ass_styles_file;
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int ass_style_override;
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int ass_hinting;
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int ass_shaper;
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int ass_justify;
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int sub_clear_on_seek;
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int teletext_page;
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};
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struct mp_osd_render_opts {
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float osd_bar_align_x;
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float osd_bar_align_y;
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float osd_bar_w;
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float osd_bar_h;
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float osd_scale;
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int osd_scale_by_window;
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struct osd_style_opts *osd_style;
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int force_rgba_osd;
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};
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typedef struct MPOpts {
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int property_print_help;
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int use_terminal;
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char *dump_stats;
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int verbose;
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int msg_really_quiet;
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char **msg_levels;
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int msg_color;
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int msg_module;
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int msg_time;
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char *log_file;
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int operation_mode;
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char **reset_options;
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char **script_files;
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char **script_opts;
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int lua_load_osc;
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int lua_load_ytdl;
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char *lua_ytdl_format;
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char **lua_ytdl_raw_options;
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int lua_load_stats;
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int auto_load_scripts;
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int audio_exclusive;
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int ao_null_fallback;
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int audio_stream_silence;
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float audio_wait_open;
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int force_vo;
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float softvol_volume;
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int rgain_mode;
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float rgain_preamp; // Set replaygain pre-amplification
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int rgain_clip; // Enable/disable clipping prevention
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float rgain_fallback;
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int softvol_mute;
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float softvol_max;
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int gapless_audio;
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mp_vo_opts *vo;
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struct ao_opts *ao_opts;
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char *wintitle;
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char *media_title;
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struct mp_csp_equalizer_opts *video_equalizer;
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int stop_screensaver;
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int cursor_autohide_delay;
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int cursor_autohide_fs;
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int video_rotate;
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char *audio_decoders;
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char *video_decoders;
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char *audio_spdif;
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struct mp_subtitle_opts *subs_rend;
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struct mp_osd_render_opts *osd_rend;
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int osd_level;
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int osd_duration;
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int osd_fractions;
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int osd_on_seek;
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int video_osd;
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int untimed;
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char *stream_dump;
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char *record_file;
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int stop_playback_on_init_failure;
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int loop_times;
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int loop_file;
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int shuffle;
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int ordered_chapters;
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char *ordered_chapters_files;
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int chapter_merge_threshold;
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double chapter_seek_threshold;
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char *chapter_file;
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int load_unsafe_playlists;
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int merge_files;
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int quiet;
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int load_config;
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char *force_configdir;
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int use_filedir_conf;
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int hls_bitrate;
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int chapterrange[2];
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int edition_id;
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int correct_pts;
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int initial_audio_sync;
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int video_sync;
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double sync_max_video_change;
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double sync_max_audio_change;
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double sync_audio_drop_size;
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int hr_seek;
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float hr_seek_demuxer_offset;
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int hr_seek_framedrop;
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float audio_delay;
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float default_max_pts_correction;
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int autosync;
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int frame_dropping;
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int video_latency_hacks;
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int term_osd;
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int term_osd_bar;
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char *term_osd_bar_chars;
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char *playing_msg;
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char *osd_playing_msg;
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char *status_msg;
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char *osd_status_msg;
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char *osd_msg[3];
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int player_idle_mode;
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int consolecontrols;
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int playlist_pos;
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struct m_rel_time play_start;
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struct m_rel_time play_end;
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struct m_rel_time play_length;
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int play_dir;
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int rebase_start_time;
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int play_frames;
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double ab_loop[2];
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double step_sec;
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int position_resume;
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int position_save_on_quit;
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int write_filename_in_watch_later_config;
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int ignore_path_in_watch_later_config;
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char *watch_later_directory;
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int pause;
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int keep_open;
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int keep_open_pause;
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double image_display_duration;
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char *lavfi_complex;
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int stream_id[2][STREAM_TYPE_COUNT];
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char **stream_lang[STREAM_TYPE_COUNT];
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int stream_auto_sel;
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int audio_display;
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char **display_tags;
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char **audio_files;
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char *demuxer_name;
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int demuxer_thread;
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double demux_termination_timeout;
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int demuxer_cache_wait;
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int prefetch_open;
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char *audio_demuxer_name;
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char *sub_demuxer_name;
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int64_t video_reverse_size;
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int64_t audio_reverse_size;
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int cache_pause;
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int cache_pause_initial;
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float cache_pause_wait;
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struct image_writer_opts *screenshot_image_opts;
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char *screenshot_template;
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char *screenshot_directory;
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double force_fps;
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int index_mode;
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struct m_channels audio_output_channels;
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int audio_output_format;
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int force_srate;
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double playback_speed;
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int pitch_correction;
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struct m_obj_settings *vf_settings, *vf_defs;
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struct m_obj_settings *af_settings, *af_defs;
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struct filter_opts *filter_opts;
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float movie_aspect;
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int aspect_method;
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char **sub_name;
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char **sub_paths;
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char **audiofile_paths;
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char **external_files;
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int autoload_files;
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int sub_auto;
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int audiofile_auto;
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int osd_bar_visible;
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int w32_priority;
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struct cdda_params *stream_cdda_opts;
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struct dvb_params *stream_dvb_opts;
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struct stream_lavf_params *stream_lavf_opts;
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char *cdrom_device;
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char *bluray_device;
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double mf_fps;
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char *mf_type;
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struct demux_rawaudio_opts *demux_rawaudio;
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struct demux_rawvideo_opts *demux_rawvideo;
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struct demux_lavf_opts *demux_lavf;
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struct demux_mkv_opts *demux_mkv;
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struct demux_opts *demux_opts;
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struct vd_lavc_params *vd_lavc_params;
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struct ad_lavc_params *ad_lavc_params;
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struct input_opts *input_opts;
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// may be NULL if encoding is not compiled-in
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struct encode_opts *encode_opts;
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char *ipc_path;
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char *input_file;
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int wingl_dwm_flush;
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struct mp_resample_opts *resample_opts;
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struct gl_video_opts *gl_video_opts;
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struct angle_opts *angle_opts;
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struct opengl_opts *opengl_opts;
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struct vulkan_opts *vulkan_opts;
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struct spirv_opts *spirv_opts;
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struct d3d11_opts *d3d11_opts;
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struct d3d11va_opts *d3d11va_opts;
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struct cocoa_opts *cocoa_opts;
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struct macos_opts *macos_opts;
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struct android_opts *android_opts;
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struct dvd_opts *dvd_opts;
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struct vaapi_opts *vaapi_opts;
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int cuda_device;
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} MPOpts;
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struct dvd_opts {
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int angle;
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int speed;
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char *device;
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};
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struct filter_opts {
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int deinterlace;
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};
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extern const m_option_t mp_opts[];
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extern const struct MPOpts mp_default_opts;
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extern const struct m_sub_options vo_sub_opts;
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extern const struct m_sub_options dvd_conf;
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extern const struct m_sub_options mp_subtitle_sub_opts;
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extern const struct m_sub_options mp_osd_render_sub_opts;
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extern const struct m_sub_options filter_conf;
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extern const struct m_sub_options resample_conf;
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#endif
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