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This starts F<mpv> with the two arguments C<--> and C<$videofile>, which
it should load and play. It then waits two seconds by starting a timer and
quits. The C<trace> argument to the constructor makes F<mpv> more verbose
and also prints the commands and responses, so you can have an idea what
is going on.

In my case, the above example would output something like this:

   [uosc] Disabled because original osc is enabled!
   mpv> {"event":"start-file","playlist_entry_id":1}
   mpv> {"event":"tracks-changed"}
    (+) Video --vid=1 (*) (h264 480x480 30.000fps)
   mpv> {"event":"metadata-update"}
   mpv> {"event":"file-loaded"}
   Using hardware decoding (nvdec).
   mpv> {"event":"video-reconfig"}
   VO: [gpu] 480x480 cuda[nv12]
   mpv> {"event":"video-reconfig"}
   mpv> {"event":"playback-restart"}

This is not usually very useful (you could just run F<mpv> as a simple
shell command), so let us load the file at runtime:

   use AnyEvent;
   use AnyEvent::MPV;
   
   my $videofile = "./xyzzy.mkv";

   my $mpv = AnyEvent::MPV->new (
      trace => 1,
      args  => ["--pause", "--idle=yes"],
   );

   $mpv->start;
   $mpv->cmd_recv (loadfile => $mpv->escape_binary ($videofile));
   $mpv->cmd ("set", "pause", "no");

   my $timer = AE::timer 2, 0, my $quit = AE::cv;
   $quit->recv;

This specifies extra arguments in the constructor - these arguments are
used every time you C<< ->start >> F<mpv>, while the arguments to C<<
->start >> are only used for this specific clal to0 C<start>. The argument
F<--pause> keeps F<mpv> in pause mode (i.e. it does not play the file
after loading it), and C<--idle=yes> tells F<mpv> to not quit when it does
not have a playlist - as no files are specified on the command line.

To load a file, we then send it a C<loadfile> command, which accepts, as
first argument, the URL or path to a video file. To make sure F<mpv> does
not misinterpret the path as a URL, it was prefixed with F<./> (similarly
to "protecting" paths in perls C<open>).

Since commands send I<to> F<mpv> are send in UTF-8, we need to escape the
filename (which might be in any encoding) using the C<esscape_binary>
method - this is not needed if your filenames are just ascii, or magically
get interpreted correctly, but if you accept arbitrary filenamews (e.g.
from the user), you need to do this.

The C<cmd_recv> method then queues the command, waits for a reply and
returns the reply data (or croaks on error). F<mpv> would, at this point,
load the file and, if everything was successful, show the first frame and
pause. Note that, since F<mpv> is implement rather synchronously itself,
do not expect commands to fail in many circumstances - for example, fit
he file does not exit, you will likely get an event, but the C<loadfile>
command itself will run successfully.

To unpause, we send another command, C<set>, to set the C<pause> property
to C<no>, this time using the C<cmd> method, which queues the command, but
instead of waiting for a reply, it immediately returns a condvar that cna
be used to receive results.

This should then cause F<mpv> to start playing the video.

It then again waits two seconds and quits.

Now, just waiting two seconds is rather, eh, unuseful, so let's look at
receiving events (using a somewhat embellished example):

   use AnyEvent;
   use AnyEvent::MPV;
   
   my $videofile = "xyzzy.mkv";

   my $quit = AE::cv;

   my $mpv = AnyEvent::MPV->new (
      trace => 1,
      args  => ["--pause", "--idle=yes"],
   );

   $mpv->start;

   $mpv->register_event (start_file => sub {
      $mpv->cmd ("set", "pause", "no");
   });

   $mpv->register_event (end_file => sub {
      my ($mpv, $event, $data) = @_;

      print "end-file<$data->{reason}>\n";
      $quit->send;
   });

   $mpv->cmd (loadfile => $mpv->escape_binary ($videofile));

   $quit->recv;

This example uses a global condvar C<$quit> to wait for the file to finish
playing. Also, most of the logic is now implement in event handlers.

The two events handlers we register are C<start-file>, which is emitted by
F<mpv> once it has loaded a new file, and C<end-file>, which signals the
end of a file (underscores are internally replaced by minus signs, so you
cna speicfy event names with either).

In the C<start-file> event, we again set the C<pause> property to C<no>
so the movie starts playing. For the C<end-file> event, we tell the main
program to quit by invoking C<$quit>.

This should conclude the basics of operation. There are a few more
examples later in the documentation.

MPV.pm  view on Meta::CPAN

   $mpv->cmd ("set", "file-local-options/chapters-file", $mpv->escape_binary ("$mpv_path.chapters"));
   $mpv->cmd ("loadfile", $mpv->escape_binary ($mpv_path));
   $mpv->cmd ("script-message", "osc-visibility", "auto", "dummy");

Handling events makes the main bulk of video playback code. For example,
various ways of ending playback:

      if ($INPUT eq "mpv/quit") { # should not happen, but allows user to kill etc. without consequence
         $status = 1;
         mpv_init; # try reinit
         last;

      } elsif ($INPUT eq "mpv/idle") { # normal end-of-file
         last;

      } elsif ($INPUT eq "return") {
         $status = 1;
         last;

Or the code that actually starts playback, once the file is loaded:

   our %SAVE_PROPERTY = (aid => 1, sid => 1, "audio-delay" => 1);
   
   ...

   my $oid = 100;

      } elsif ($INPUT eq "mpv/file-loaded") { # start playing, configure video
         $mpv->cmd ("seek", $playback_start, "absolute+exact") if $playback_start > 0;

         my $target_fps = eval { $mpv->cmd_recv ("get_property", "container-fps") } || 60;
         $target_fps *= play_video_speed_mult;
         set_fps $target_fps;

         unless (eval { $mpv->cmd_recv ("get_property", "video-format") }) {
            $mpv->cmd ("set", "file-local-options/lavfi-complex", "[aid1] asplit [ao], showcqt=..., format=yuv420p [vo]");
         };

         for my $prop (keys %SAVE_PROPERTY) {
            if (exists $PLAYING_STATE->{"mpv_$prop"}) {
               $mpv->cmd ("set", "$prop", $PLAYING_STATE->{"mpv_$prop"} . "");
            }

            $mpv->cmd ("observe_property", ++$oid, $prop);
         }

         play_video_set_speed;
         $mpv->cmd ("set", "osd-level", "$OSD_LEVEL");
         $mpv->cmd ("observe_property", ++$oid, "osd-level");
         $mpv->cmd ("set", "pause", "no");

         $mpv->cmd ("set_property", "deinterlace", "yes")
            if $initial_deinterlace;

There is a lot going on here. First it seeks to the actual playback
position, if it is not at the start of the file (it would probaby be more
efficient to set the starting position before loading the file, though,
but this is good enough).

Then it plays with the display fps, to set it to something harmonious
w.r.t. the video framerate.

If the file does not have a video part, it assumes it is an audio file and
sets a visualizer.

Also, a number of properties are not global, but per-file. At the moment,
this is C<audio-delay>, and the current audio/subtitle track, which it
sets, and also creates an observer. Again, this doesn'T use the observe
functionality of this module, but handles it itself, assigning obsevrer
ids 100+ to temporary/per-file observers.

Lastly, it sets some global (or per-youtube-uploader) parameters, such as
speed, and unpauses. Property changes are handled like other input events:

      } elsif ($INPUT eq "mpv/property-change") {
         my $prop = $INPUT_DATA->{name};

         if ($prop eq "chapter-metadata") {
            if ($INPUT_DATA->{data}{TITLE} =~ /^\[SponsorBlock\]: (.*)/) {
               my $section = $1;
               my $skip;

               $skip ||= $SPONSOR_SKIP{$_}
                  for split /\s*,\s*/, $section;

               if (defined $skip) {
                  if ($skip) {
                     # delay a bit, in case we get two metadata changes in quick succession, e.g.
                     # because we have a skip at file load time.
                     $skip_delay = AE::timer 2/50, 0, sub {
                        $mpv->cmd ("no-osd", "add", "chapter", 1);
                        $mpv->cmd ("show-text", "skipped sponsorblock section \"$section\"", 3000);
                     };
                  } else {
                     undef $skip_delay;
                     $mpv->cmd ("show-text", "NOT skipping sponsorblock section \"$section\"", 3000);
                  }
               } else {
                  $mpv->cmd ("show-text", "UNRECOGNIZED sponsorblock section \"$section\"", 60000);
               }
            } else {
               # cancel a queued skip
               undef $skip_delay;
            }

         } elsif (exists $SAVE_PROPERTY{$prop}) {
            $PLAYING_STATE->{"mpv_$prop"} = $INPUT_DATA->{data};
            ::state_save;
         }

This saves back the per-file properties, and also handles chapter changes
in a hacky way.

Most of the handlers are very simple, though. For example:

      } elsif ($INPUT eq "pause") {
         $mpv->cmd ("cycle", "pause");
         $PLAYING_STATE->{curpos} = $mpv->cmd_recv ("get_property", "playback-time");
      } elsif ($INPUT eq "right") {
         $mpv->cmd ("osd-msg-bar", "seek",  30, "relative+exact");
      } elsif ($INPUT eq "left") {
         $mpv->cmd ("osd-msg-bar", "seek", -5, "relative+exact");
      } elsif ($INPUT eq "up") {
         $mpv->cmd ("osd-msg-bar", "seek", +600, "relative+exact");
      } elsif ($INPUT eq "down") {
         $mpv->cmd ("osd-msg-bar", "seek", -600, "relative+exact");
      } elsif ($INPUT eq "select") {
         $mpv->cmd ("osd-msg-bar", "add", "audio-delay", "-0.100");
      } elsif ($INPUT eq "start") {
         $mpv->cmd ("osd-msg-bar", "add", "audio-delay", "0.100");
      } elsif ($INPUT eq "intfwd") {
         $mpv->cmd ("no-osd", "frame-step");
      } elsif ($INPUT eq "audio") {
         $mpv->cmd ("osd-auto", "cycle", "audio");
      } elsif ($INPUT eq "subtitle") {
         $mpv->cmd ("osd-auto", "cycle", "sub");
      } elsif ($INPUT eq "triangle") {
         $mpv->cmd ("osd-auto", "cycle", "deinterlace");

Once a file has finished playing (or the user strops playback), it pauses,
unobserves the per-file observers, and saves the current position for to
be able to resume:

   $mpv->cmd ("set", "pause", "yes");

   while ($oid > 100) {
      $mpv->cmd ("unobserve_property", $oid--);
   }

   $PLAYING_STATE->{curpos} = $mpv->cmd_recv ("get_property", "playback-time");

And thats most of the F<mpv>-related code.

=head2 F<Gtk2::CV>

F<Gtk2::CV> is low-feature image viewer that I use many times daily
because it can handle directories with millions of files without falling
over. It also had the ability to play videos for ages, but it used an
older, crappier protocol to talk to F<mpv> and used F<ffprobe> before
playing each file instead of letting F<mpv> handle format/size detection.

After writing this module, I decided to upgprade Gtk2::CV by making use
of it, with the goal of getting rid of F<ffprobe> and being ablew to
reuse F<mpv> processes, which would have a multitude of speed benefits
(for example, fork+exec of F<mpv> caused the kernel to close all file
descriptors, which could take minutes if a large file was being copied via
NFS, as the kernel waited for thr buffers to be flushed on close - not
having to start F<mpv> gets rid of this issue).

Setting up is only complicated by the fact that F<mpv> needs to be
embedded into an existing window. To keep control of all inputs,
F<Gtk2::CV> puts an eventbox in front of F<mpv>, so F<mpv> receives no
input events:

   $self->{mpv} = AnyEvent::MPV->new (
      trace => $ENV{CV_MPV_TRACE},
   );

   # create an eventbox, so we receive all input events
   my $box = $self->{mpv_eventbox} = new Gtk2::EventBox;
   $box->set_above_child (1);
   $box->set_visible_window (0);
   $box->set_events ([]);
   $box->can_focus (0);

   # create a drawingarea that mpv can display into
   my $window = $self->{mpv_window} = new Gtk2::DrawingArea;
   $box->add ($window);

   # put the drawingarea intot he eventbox, and the eventbox into our display window
   $self->add ($box);