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mirror of https://github.com/mpv-player/mpv synced 2025-01-14 02:51:26 +00:00
mpv/player/main.c
wm4 b9d351f02a Implement backwards playback
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.
2019-09-19 20:37:04 +02:00

486 lines
15 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 <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <math.h>
#include <assert.h>
#include <string.h>
#include <pthread.h>
#include <locale.h>
#include "config.h"
#include "mpv_talloc.h"
#include "misc/dispatch.h"
#include "misc/thread_pool.h"
#include "osdep/io.h"
#include "osdep/terminal.h"
#include "osdep/timer.h"
#include "osdep/main-fn.h"
#include "common/av_log.h"
#include "common/codecs.h"
#include "common/encode.h"
#include "options/m_config.h"
#include "options/m_option.h"
#include "options/m_property.h"
#include "common/common.h"
#include "common/msg.h"
#include "common/msg_control.h"
#include "common/global.h"
#include "filters/f_decoder_wrapper.h"
#include "options/parse_configfile.h"
#include "options/parse_commandline.h"
#include "common/playlist.h"
#include "options/options.h"
#include "options/path.h"
#include "input/input.h"
#include "audio/out/ao.h"
#include "demux/demux.h"
#include "misc/thread_tools.h"
#include "sub/osd.h"
#include "video/out/vo.h"
#include "core.h"
#include "client.h"
#include "command.h"
#include "screenshot.h"
static const char def_config[] =
#include "player/builtin_conf.inc"
;
#if HAVE_COCOA
#include "osdep/macosx_events.h"
#endif
#ifndef FULLCONFIG
#define FULLCONFIG "(missing)\n"
#endif
#if !HAVE_STDATOMIC
pthread_mutex_t mp_atomic_mutex = PTHREAD_MUTEX_INITIALIZER;
#endif
enum exit_reason {
EXIT_NONE,
EXIT_NORMAL,
EXIT_ERROR,
};
const char mp_help_text[] =
"Usage: mpv [options] [url|path/]filename\n"
"\n"
"Basic options:\n"
" --start=<time> seek to given (percent, seconds, or hh:mm:ss) position\n"
" --no-audio do not play sound\n"
" --no-video do not play video\n"
" --fs fullscreen playback\n"
" --sub-file=<file> specify subtitle file to use\n"
" --playlist=<file> specify playlist file\n"
"\n"
" --list-options list all mpv options\n"
" --h=<string> print options which contain the given string in their name\n"
"\n";
static pthread_mutex_t terminal_owner_lock = PTHREAD_MUTEX_INITIALIZER;
static struct MPContext *terminal_owner;
static bool cas_terminal_owner(struct MPContext *old, struct MPContext *new)
{
pthread_mutex_lock(&terminal_owner_lock);
bool r = terminal_owner == old;
if (r)
terminal_owner = new;
pthread_mutex_unlock(&terminal_owner_lock);
return r;
}
void mp_update_logging(struct MPContext *mpctx, bool preinit)
{
bool had_log_file = mp_msg_has_log_file(mpctx->global);
mp_msg_update_msglevels(mpctx->global, mpctx->opts);
bool enable = mpctx->opts->use_terminal;
bool enabled = cas_terminal_owner(mpctx, mpctx);
if (enable != enabled) {
if (enable && cas_terminal_owner(NULL, mpctx)) {
terminal_init();
enabled = true;
} else if (!enable) {
terminal_uninit();
cas_terminal_owner(mpctx, NULL);
}
}
if (mp_msg_has_log_file(mpctx->global) && !had_log_file)
mp_print_version(mpctx->log, false); // for log-file=... in config files
if (enabled && !preinit && mpctx->opts->consolecontrols)
terminal_setup_getch(mpctx->input);
}
void mp_print_version(struct mp_log *log, int always)
{
int v = always ? MSGL_INFO : MSGL_V;
mp_msg(log, v, "%s %s\n built on %s\n",
mpv_version, mpv_copyright, mpv_builddate);
print_libav_versions(log, v);
mp_msg(log, v, "\n");
// Only in verbose mode.
if (!always) {
mp_msg(log, MSGL_V, "Configuration: " CONFIGURATION "\n");
mp_msg(log, MSGL_V, "List of enabled features: %s\n", FULLCONFIG);
#ifdef NDEBUG
mp_msg(log, MSGL_V, "Built with NDEBUG.\n");
#endif
}
}
void mp_destroy(struct MPContext *mpctx)
{
mp_shutdown_clients(mpctx);
mp_uninit_ipc(mpctx->ipc_ctx);
mpctx->ipc_ctx = NULL;
uninit_audio_out(mpctx);
uninit_video_out(mpctx);
// If it's still set here, it's an error.
encode_lavc_free(mpctx->encode_lavc_ctx);
mpctx->encode_lavc_ctx = NULL;
command_uninit(mpctx);
mp_clients_destroy(mpctx);
osd_free(mpctx->osd);
#if HAVE_COCOA
cocoa_set_input_context(NULL);
#endif
if (cas_terminal_owner(mpctx, mpctx)) {
terminal_uninit();
cas_terminal_owner(mpctx, NULL);
}
mp_input_uninit(mpctx->input);
uninit_libav(mpctx->global);
mp_msg_uninit(mpctx->global);
assert(!mpctx->num_abort_list);
talloc_free(mpctx->abort_list);
pthread_mutex_destroy(&mpctx->abort_lock);
talloc_free(mpctx);
}
static bool handle_help_options(struct MPContext *mpctx)
{
struct MPOpts *opts = mpctx->opts;
struct mp_log *log = mpctx->log;
if (opts->audio_decoders && strcmp(opts->audio_decoders, "help") == 0) {
struct mp_decoder_list *list = audio_decoder_list();
mp_print_decoders(log, MSGL_INFO, "Audio decoders:", list);
talloc_free(list);
return true;
}
if (opts->audio_spdif && strcmp(opts->audio_spdif, "help") == 0) {
MP_INFO(mpctx, "Choices: ac3,dts-hd,dts (and possibly more)\n");
return true;
}
if (opts->video_decoders && strcmp(opts->video_decoders, "help") == 0) {
struct mp_decoder_list *list = video_decoder_list();
mp_print_decoders(log, MSGL_INFO, "Video decoders:", list);
talloc_free(list);
return true;
}
if ((opts->demuxer_name && strcmp(opts->demuxer_name, "help") == 0) ||
(opts->audio_demuxer_name && strcmp(opts->audio_demuxer_name, "help") == 0) ||
(opts->sub_demuxer_name && strcmp(opts->sub_demuxer_name, "help") == 0)) {
demuxer_help(log);
MP_INFO(mpctx, "\n");
return true;
}
if (opts->ao_opts->audio_device &&
strcmp(opts->ao_opts->audio_device, "help") == 0)
{
ao_print_devices(mpctx->global, log);
return true;
}
if (opts->property_print_help) {
property_print_help(mpctx);
return true;
}
if (encode_lavc_showhelp(log, opts->encode_opts))
return true;
return false;
}
static int cfg_include(void *ctx, char *filename, int flags)
{
struct MPContext *mpctx = ctx;
char *fname = mp_get_user_path(NULL, mpctx->global, filename);
int r = m_config_parse_config_file(mpctx->mconfig, fname, NULL, flags);
talloc_free(fname);
return r;
}
// We mostly care about LC_NUMERIC, and how "." vs. "," is treated,
// Other locale stuff might break too, but probably isn't too bad.
static bool check_locale(void)
{
char *name = setlocale(LC_NUMERIC, NULL);
return !name || strcmp(name, "C") == 0 || strcmp(name, "C.UTF-8") == 0;
}
struct MPContext *mp_create(void)
{
if (!check_locale()) {
// Normally, we never print anything (except if the "terminal" option
// is enabled), so this is an exception.
fprintf(stderr, "Non-C locale detected. This is not supported.\n"
"Call 'setlocale(LC_NUMERIC, \"C\");' in your code.\n");
return NULL;
}
char *enable_talloc = getenv("MPV_LEAK_REPORT");
if (enable_talloc && strcmp(enable_talloc, "1") == 0)
talloc_enable_leak_report();
mp_time_init();
struct MPContext *mpctx = talloc(NULL, MPContext);
*mpctx = (struct MPContext){
.last_chapter = -2,
.term_osd_contents = talloc_strdup(mpctx, ""),
.osd_progbar = { .type = -1 },
.playlist = talloc_struct(mpctx, struct playlist, {0}),
.dispatch = mp_dispatch_create(mpctx),
.playback_abort = mp_cancel_new(mpctx),
.thread_pool = mp_thread_pool_create(mpctx, 0, 1, 30),
.stop_play = PT_STOP,
.play_dir = 1,
};
pthread_mutex_init(&mpctx->abort_lock, NULL);
mpctx->global = talloc_zero(mpctx, struct mpv_global);
// Nothing must call mp_msg*() and related before this
mp_msg_init(mpctx->global);
mpctx->log = mp_log_new(mpctx, mpctx->global->log, "!cplayer");
mpctx->statusline = mp_log_new(mpctx, mpctx->log, "!statusline");
// Create the config context and register the options
mpctx->mconfig = m_config_new(mpctx, mpctx->log, sizeof(struct MPOpts),
&mp_default_opts, mp_opts);
mpctx->opts = mpctx->mconfig->optstruct;
mpctx->mconfig->includefunc = cfg_include;
mpctx->mconfig->includefunc_ctx = mpctx;
mpctx->mconfig->use_profiles = true;
mpctx->mconfig->is_toplevel = true;
mpctx->mconfig->global = mpctx->global;
m_config_parse(mpctx->mconfig, "", bstr0(def_config), NULL, 0);
m_config_create_shadow(mpctx->mconfig);
mpctx->input = mp_input_init(mpctx->global, mp_wakeup_core_cb, mpctx);
screenshot_init(mpctx);
command_init(mpctx);
init_libav(mpctx->global);
mp_clients_init(mpctx);
mpctx->osd = osd_create(mpctx->global);
#if HAVE_COCOA
cocoa_set_input_context(mpctx->input);
#endif
char *verbose_env = getenv("MPV_VERBOSE");
if (verbose_env)
mpctx->opts->verbose = atoi(verbose_env);
return mpctx;
}
// Finish mpctx initialization. This must be done after setting up all options.
// Some of the initializations depend on the options, and can't be changed or
// undone later.
// If options is not NULL, apply them as command line player arguments.
// Returns: 0 on success, -1 on error, 1 if exiting normally (e.g. help).
int mp_initialize(struct MPContext *mpctx, char **options)
{
struct MPOpts *opts = mpctx->opts;
assert(!mpctx->initialized);
// Preparse the command line, so we can init the terminal early.
if (options) {
m_config_preparse_command_line(mpctx->mconfig, mpctx->global,
&opts->verbose, options);
}
mp_init_paths(mpctx->global, opts);
mp_update_logging(mpctx, true);
if (options) {
MP_VERBOSE(mpctx, "Command line options:");
for (int i = 0; options[i]; i++)
MP_VERBOSE(mpctx, " '%s'", options[i]);
MP_VERBOSE(mpctx, "\n");
}
mp_print_version(mpctx->log, false);
mp_parse_cfgfiles(mpctx);
if (options) {
int r = m_config_parse_mp_command_line(mpctx->mconfig, mpctx->playlist,
mpctx->global, options);
if (r < 0)
return r == M_OPT_EXIT ? 1 : -1;
}
if (opts->operation_mode == 1) {
m_config_set_profile(mpctx->mconfig, "builtin-pseudo-gui",
M_SETOPT_NO_OVERWRITE);
m_config_set_profile(mpctx->mconfig, "pseudo-gui", 0);
}
mp_get_resume_defaults(mpctx);
mp_input_load_config(mpctx->input);
// From this point on, all mpctx members are initialized.
mpctx->initialized = true;
mpctx->mconfig->option_set_callback = mp_on_set_option;
mpctx->mconfig->option_set_callback_cb = mpctx;
mpctx->mconfig->option_change_callback = mp_option_change_callback;
mpctx->mconfig->option_change_callback_ctx = mpctx;
// Run all update handlers.
mp_option_change_callback(mpctx, NULL, UPDATE_OPTS_MASK);
if (handle_help_options(mpctx))
return 1; // help
if (!print_libav_versions(mp_null_log, 0)) {
// Using mismatched libraries can be legitimate, but even then it's
// a bad idea. We don't acknowledge its usefulness and stability.
// Distro maintainers who patch this out should be aware that mpv
// intentionally ignores ABI in some places where it's not possible to
// get by without violating it.
print_libav_versions(mpctx->log, MSGL_FATAL);
MP_FATAL(mpctx, "\nmpv was compiled against a different version of "
"FFmpeg/Libav than the shared\nlibrary it is linked against. "
"This is most likely a broken build and could\nresult in "
"misbehavior and crashes.\n\nmpv does not support this "
"configuration and will not run - rebuild mpv instead.\n");
return -1;
}
if (!mpctx->playlist->first && !opts->player_idle_mode) {
// nothing to play
mp_print_version(mpctx->log, true);
MP_INFO(mpctx, "%s", mp_help_text);
return 1;
}
MP_STATS(mpctx, "start init");
#if HAVE_COCOA
mpv_handle *ctx = mp_new_client(mpctx->clients, "osx");
cocoa_set_mpv_handle(ctx);
#endif
if (opts->encode_opts->file && opts->encode_opts->file[0]) {
mpctx->encode_lavc_ctx = encode_lavc_init(mpctx->global);
if(!mpctx->encode_lavc_ctx) {
MP_INFO(mpctx, "Encoding initialization failed.\n");
return -1;
}
m_config_set_profile(mpctx->mconfig, "encoding", 0);
mp_input_enable_section(mpctx->input, "encode", MP_INPUT_EXCLUSIVE);
}
#if !HAVE_LIBASS
MP_WARN(mpctx, "Compiled without libass.\n");
MP_WARN(mpctx, "There will be no OSD and no text subtitles.\n");
#endif
mp_load_scripts(mpctx);
if (opts->force_vo == 2 && handle_force_window(mpctx, false) < 0)
return -1;
MP_STATS(mpctx, "end init");
return 0;
}
int mpv_main(int argc, char *argv[])
{
struct MPContext *mpctx = mp_create();
if (!mpctx)
return 1;
mpctx->is_cli = true;
char **options = argv && argv[0] ? argv + 1 : NULL; // skips program name
int r = mp_initialize(mpctx, options);
if (r == 0)
mp_play_files(mpctx);
int rc = 0;
const char *reason = NULL;
if (r < 0) {
reason = "Fatal error";
rc = 1;
} else if (r > 0) {
// nothing
} else if (mpctx->stop_play == PT_QUIT) {
reason = "Quit";
} else if (mpctx->files_played) {
if (mpctx->files_errored || mpctx->files_broken) {
reason = "Some errors happened";
rc = 3;
} else {
reason = "End of file";
}
} else if (mpctx->files_broken && !mpctx->files_errored) {
reason = "Errors when loading file";
rc = 2;
} else if (mpctx->files_errored) {
reason = "Interrupted by error";
rc = 2;
} else {
reason = "No files played";
}
if (reason)
MP_INFO(mpctx, "\nExiting... (%s)\n", reason);
if (mpctx->has_quit_custom_rc)
rc = mpctx->quit_custom_rc;
mp_destroy(mpctx);
return rc;
}