lua.rst

LUA SCRIPTING

mpv can load Lua scripts. Scripts passed to the --script option, or found in the scripts subdirectory of the mpv configuration directory (usually ~/.config/mpv/scripts/) will be loaded on program start. mpv also appends the scripts subdirectory to the end of Lua's path so you can import scripts from there too. Since it's added to the end, don't name scripts you want to import the same as Lua libraries because they will be overshadowed by them.

mpv provides the built-in module mp, which contains functions to send commands to the mpv core and to retrieve information about playback state, user settings, file information, and so on.

These scripts can be used to control mpv in a similar way to slave mode. Technically, the Lua code uses the client API internally.

Example

A script which leaves fullscreen mode when the player is paused:

function on_pause_change(name, value)
    if value == true then
        mp.set_property("fullscreen", "no")
    end
end
mp.observe_property("pause", "bool", on_pause_change)

Details on the script initialization and lifecycle

Your script will be loaded by the player at program start from the scripts configuration subdirectory, or from a path specified with the --script option. Some scripts are loaded internally (like --osc). Each script runs in its own thread. Your script is first run "as is", and once that is done, the event loop is entered. This event loop will dispatch events received by mpv and call your own event handlers which you have registered with mp.register_event, or timers added with mp.add_timeout or similar.

When the player quits, all scripts will be asked to terminate. This happens via a shutdown event, which by default will make the event loop return. If your script got into an endless loop, mpv will probably behave fine during playback, but it won't terminate when quitting, because it's waiting on your script.

Internally, the C code will call the Lua function mp_event_loop after loading a Lua script. This function is normally defined by the default prelude loaded before your script (see player/lua/defaults.lua in the mpv sources). The event loop will wait for events and dispatch events registered with mp.register_event. It will also handle timers added with mp.add_timeout and similar (by waiting with a timeout).

Since mpv 0.6.0, the player will wait until the script is fully loaded before continuing normal operation. The player considers a script as fully loaded as soon as it starts waiting for mpv events (or it exits). In practice this means the player will more or less hang until the script returns from the main chunk (and mp_event_loop is called), or the script calls mp_event_loop or mp.dispatch_events directly. This is done to make it possible for a script to fully setup event handlers etc. before playback actually starts. In older mpv versions, this happened asynchronously.

mp functions

The mp module is preloaded, although it can be loaded manually with require 'mp'. It provides the core client API.

mp.command(string)

Run the given command. This is similar to the commands used in input.conf. See `List of Input Commands`_.

By default, this will show something on the OSD (depending on the command), as if it was used in input.conf. See `Input Command Prefixes`_ how to influence OSD usage per command.

Returns true on success, or nil, error on error.

mp.commandv(arg1, arg2, ...)

Similar to mp.command, but pass each command argument as separate parameter. This has the advantage that you don't have to care about quoting and escaping in some cases.

Example:

mp.command("loadfile " .. filename .. " append")
mp.commandv("loadfile", filename, "append")

These two commands are equivalent, except that the first version breaks if the filename contains spaces or certain special characters.

Note that properties are not expanded. You can use either mp.command, the expand-properties prefix, or the mp.get_property family of functions.

Unlike mp.command, this will not use OSD by default either (except for some OSD-specific commands).

mp.command_native(table [,def])

Similar to mp.commandv, but pass the argument list as table. This has the advantage that in at least some cases, arguments can be passed as native types.

Returns a result table on success (usually empty), or def, error on error. def is the second parameter provided to the function, and is nil if it's missing.

mp.get_property(name [,def])

Return the value of the given property as string. These are the same properties as used in input.conf. See `Properties`_ for a list of properties. The returned string is formatted similar to ${=name} (see `Property Expansion`_).

Returns the string on success, or def, error on error. def is the second parameter provided to the function, and is nil if it's missing.

mp.get_property_osd(name [,def])

Similar to mp.get_property, but return the property value formatted for OSD. This is the same string as printed with ${name} when used in input.conf.

Returns the string on success, or def, error on error. def is the second parameter provided to the function, and is an empty string if it's missing. Unlike get_property(), assigning the return value to a variable will always result in a string.

mp.get_property_bool(name [,def])

Similar to mp.get_property, but return the property value as Boolean.

Returns a Boolean on success, or def, error on error.

mp.get_property_number(name [,def])

Similar to mp.get_property, but return the property value as number.

Note that while Lua does not distinguish between integers and floats, mpv internals do. This function simply request a double float from mpv, and mpv will usually convert integer property values to float.

Returns a number on success, or def, error on error.

mp.get_property_native(name [,def])

Similar to mp.get_property, but return the property value using the best Lua type for the property. Most time, this will return a string, Boolean, or number. Some properties (for example chapter-list) are returned as tables.

Returns a value on success, or def, error on error. Note that nil might be a possible, valid value too in some corner cases.

mp.set_property(name, value)

Set the given property to the given string value. See mp.get_property and `Properties`_ for more information about properties.

Returns true on success, or nil, error on error.

mp.set_property_bool(name, value)

Similar to mp.set_property, but set the given property to the given Boolean value.

mp.set_property_number(name, value)

Similar to mp.set_property, but set the given property to the given numeric value.

Note that while Lua does not distinguish between integers and floats, mpv internals do. This function will test whether the number can be represented as integer, and if so, it will pass an integer value to mpv, otherwise a double float.

mp.set_property_native(name, value)

Similar to mp.set_property, but set the given property using its native type.

Since there are several data types which cannot represented natively in Lua, this might not always work as expected. For example, while the Lua wrapper can do some guesswork to decide whether a Lua table is an array or a map, this would fail with empty tables. Also, there are not many properties for which it makes sense to use this, instead of set_property, set_property_bool, set_property_number. For these reasons, this function should probably be avoided for now, except for properties that use tables natively.

mp.get_time()

Return the current mpv internal time in seconds as a number. This is basically the system time, with an arbitrary offset.

mp.add_key_binding(key, name|fn [,fn [,flags]])

Register callback to be run on a key binding. The binding will be mapped to the given key, which is a string describing the physical key. This uses the same key names as in input.conf, and also allows combinations (e.g. ctrl+a). If the key is empty or nil, no physical key is registered, but the user still can create own bindings (see below).

After calling this function, key presses will cause the function fn to be called (unless the user remapped the key with another binding).

The name argument should be a short symbolic string. It allows the user to remap the key binding via input.conf using the script-message command, and the name of the key binding (see below for an example). The name should be unique across other bindings in the same script - if not, the previous binding with the same name will be overwritten. You can omit the name, in which case a random name is generated internally.

The last argument is used for optional flags. This is a table, which can have the following entries:

repeatable

If set to true, enables key repeat for this specific binding.

complex

If set to true, then fn is called on both key up and down events (as well as key repeat, if enabled), with the first argument being a table. This table has an event entry, which is set to one of the strings down, repeat, up or press (the latter if key up/down can't be tracked). It further has an is_mouse entry, which tells whether the event was caused by a mouse button.

Internally, key bindings are dispatched via the script-message-to or script-binding input commands and mp.register_script_message.

Trying to map multiple commands to a key will essentially prefer a random binding, while the other bindings are not called. It is guaranteed that user defined bindings in the central input.conf are preferred over bindings added with this function (but see mp.add_forced_key_binding).

Example:

function something_handler()
    print("the key was pressed")
end
mp.add_key_binding("x", "something", something_handler)

This will print the message the key was pressed when x was pressed.

The user can remap these key bindings. Then the user has to put the following into their input.conf to remap the command to the y key:

y script-binding something

This will print the message when the key y is pressed. (x will still work, unless the user remaps it.)

You can also explicitly send a message to a named script only. Assume the above script was using the filename fooscript.lua:

y script-binding fooscript/something

mp.add_forced_key_binding(...)

This works almost the same as mp.add_key_binding, but registers the key binding in a way that will overwrite the user's custom bindings in their input.conf. (mp.add_key_binding overwrites default key bindings only, but not those by the user's input.conf.)

mp.remove_key_binding(name)

Remove a key binding added with mp.add_key_binding or mp.add_forced_key_binding. Use the same name as you used when adding the bindings. It's not possible to remove bindings for which you omitted the name.

mp.register_event(name, fn)

Call a specific function when an event happens. The event name is a string, and the function fn is a Lua function value.

Some events have associated data. This is put into a Lua table and passed as argument to fn. The Lua table by default contains a name field, which is a string containing the event name. If the event has an error associated, the error field is set to a string describing the error, on success it's not set.

If multiple functions are registered for the same event, they are run in registration order, which the first registered function running before all the other ones.

Returns true if such an event exists, false otherwise.

See Events and List of events for details.

mp.unregister_event(fn)

Undo mp.register_event(..., fn). This removes all event handlers that are equal to the fn parameter. This uses normal Lua == comparison, so be careful when dealing with closures.

mp.observe_property(name, type, fn)

Watch a property for changes. If the property name is changed, then the function fn(name) will be called. type can be nil, or be set to one of none, native, bool, string, or number. none is the same as nil. For all other values, the new value of the property will be passed as second argument to fn, using mp.get_property_<type> to retrieve it. This means if type is for example string, fn is roughly called as in fn(name, mp.get_property_string(name)).

If possible, change events are coalesced. If a property is changed a bunch of times in a row, only the last change triggers the change function. (The exact behavior depends on timing and other things.)

In some cases the function is not called even if the property changes. Whether this can happen depends on the property.

If the type is none or nil, sporadic property change events are possible. This means the change function fn can be called even if the property doesn't actually change.

mp.unobserve_property(fn)

Undo mp.observe_property(..., fn). This removes all property handlers that are equal to the fn parameter. This uses normal Lua == comparison, so be careful when dealing with closures.

mp.add_timeout(seconds, fn)

Call the given function fn when the given number of seconds has elapsed. Note that the number of seconds can be fractional. For now, the timer's resolution may be as low as 50 ms, although this will be improved in the future.

This is a one-shot timer: it will be removed when it's fired.

Returns a timer object. See mp.add_periodic_timer for details.

mp.add_periodic_timer(seconds, fn)

Call the given function periodically. This is like mp.add_timeout, but the timer is re-added after the function fn is run.

Returns a timer object. The timer object provides the following methods:

stop()

Disable the timer. Does nothing if the timer is already disabled. This will remember the current elapsed time when stopping, so that resume() essentially unpauses the timer.

kill()

Disable the timer. Resets the elapsed time. resume() will restart the timer.

resume()

Restart the timer. If the timer was disabled with stop(), this will resume at the time it was stopped. If the timer was disabled with kill(), or if it's a previously fired one-shot timer (added with add_timeout()), this starts the timer from the beginning, using the initially configured timeout.

is_enabled()

Whether the timer is currently enabled or was previously disabled (e.g. by stop() or kill()).

timeout (RW)

This field contains the current timeout period. This value is not updated as time progresses. It's only used to calculate when the timer should fire next when the timer expires.

If you write this, you can call t:kill() ; t:resume() to reset the current timeout to the new one. (t:stop() won't use the new timeout.)

oneshot (RW)

Whether the timer is periodic (false) or fires just once (true). This value is used when the timer expires (but before the timer callback function fn is run).

Note that these are method, and you have to call them using : instead of . (Refer to http://www.lua.org/manual/5.2/manual.html#3.4.9 .)

Example:

seconds = 0
timer = mp.add_periodic_timer(1, function()
    print("called every second")
    # stop it after 10 seconds
    seconds = seconds + 1
    if seconds >= 10 then
        timer:kill()
    end
end)

mp.get_opt(key)

Return a setting from the --script-opts option. It's up to the user and the script how this mechanism is used. Currently, all scripts can access this equally, so you should be careful about collisions.

mp.get_script_name()

Return the name of the current script. The name is usually made of the filename of the script, with directory and file extension removed. If there are several scripts which would have the same name, it's made unique by appending a number.

Example

The script /path/to/fooscript.lua becomes fooscript.

mp.osd_message(text [,duration])

Show an OSD message on the screen. duration is in seconds, and is optional (uses --osd-duration by default).

Advanced mp functions

These also live in the mp module, but are documented separately as they are useful only in special situations.

mp.suspend()

This function has been deprecated in mpv 0.21.0 and does nothing starting with mpv 0.23.0 (no replacement).

mp.resume()

This function has been deprecated in mpv 0.21.0 and does nothing starting with mpv 0.23.0 (no replacement).

mp.resume_all()

This function has been deprecated in mpv 0.21.0 and does nothing starting with mpv 0.23.0 (no replacement).

mp.get_wakeup_pipe()

Calls mpv_get_wakeup_pipe() and returns the read end of the wakeup pipe. (See client.h for details.)

mp.get_next_timeout()

Return the relative time in seconds when the next timer (mp.add_timeout and similar) expires. If there is no timer, return nil.

mp.dispatch_events([allow_wait])

This can be used to run custom event loops. If you want to have direct control what the Lua script does (instead of being called by the default event loop), you can set the global variable mp_event_loop to your own function running the event loop. From your event loop, you should call mp.dispatch_events() to dequeue and dispatch mpv events.

If the allow_wait parameter is set to true, the function will block until the next event is received or the next timer expires. Otherwise (and this is the default behavior), it returns as soon as the event loop is emptied. It's strongly recommended to use mp.get_next_timeout() and mp.get_wakeup_pipe() if you're interested in properly working notification of new events and working timers.

mp.register_idle(fn)

Register an event loop idle handler. Idle handlers are called before the script goes to sleep after handling all new events. This can be used for example to delay processing of property change events: if you're observing multiple properties at once, you might not want to act on each property change, but only when all change notifications have been received.

mp.unregister_idle(fn)

Undo mp.register_idle(fn). This removes all idle handlers that are equal to the fn parameter. This uses normal Lua == comparison, so be careful when dealing with closures.

mp.enable_messages(level)

Set the minimum log level of which mpv message output to receive. These messages are normally printed to the terminal. By calling this function, you can set the minimum log level of messages which should be received with the log-message event. See the description of this event for details. The level is a string, see msg.log for allowed log levels.

mp.register_script_message(name, fn)

This is a helper to dispatch script-message or script-message-to invocations to Lua functions. fn is called if script-message or script-message-to (with this script as destination) is run with name as first parameter. The other parameters are passed to fn. If a message with the given name is already registered, it's overwritten.

Used by mp.add_key_binding, so be careful about name collisions.

mp.unregister_script_message(name)

Undo a previous registration with mp.register_script_message. Does nothing if the name wasn't registered.

mp.msg functions

This module allows outputting messages to the terminal, and can be loaded with require 'mp.msg'.

msg.log(level, ...)

The level parameter is the message priority. It's a string and one of fatal, error, warn, info, v, debug. The user's settings will determine which of these messages will be visible. Normally, all messages are visible, except v and debug.

The parameters after that are all converted to strings. Spaces are inserted to separate multiple parameters.

You don't need to add newlines.

msg.fatal(...), msg.error(...), msg.warn(...), msg.info(...), msg.verbose(...), msg.debug(...)

All of these are shortcuts and equivalent to the corresponding msg.log(level, ...) call.

mp.options functions

mpv comes with a built-in module to manage options from config-files and the command-line. All you have to do is to supply a table with default options to the read_options function. The function will overwrite the default values with values found in the config-file and the command-line (in that order).

options.read_options(table [, identifier])

A table with key-value pairs. The type of the default values is important for converting the values read from the config file or command-line back. Do not use nil as a default value!

The identifier is used to identify the config-file and the command-line options. These needs to unique to avoid collisions with other scripts. Defaults to mp.get_script_name().

Example implementation:

require 'mp.options'
local options = {
    optionA = "defaultvalueA",
    optionB = -0.5,
    optionC = true,
}
read_options(options, "myscript")
print(options.optionA)

The config file will be stored in lua-settings/identifier.conf in mpv's user folder. Comment lines can be started with # and stray spaces are not removed. Boolean values will be represented with yes/no.

Example config:

# comment
optionA=Hello World
optionB=9999
optionC=no

Command-line options are read from the --script-opts parameter. To avoid collisions, all keys have to be prefixed with identifier-.

Example command-line:

--script-opts=myscript-optionA=TEST,myscript-optionB=0,myscript-optionC=yes

mp.utils functions

This built-in module provides generic helper functions for Lua, and have strictly speaking nothing to do with mpv or video/audio playback. They are provided for convenience. Most compensate for Lua's scarce standard library.

Be warned that any of these functions might disappear any time. They are not strictly part of the guaranteed API.

utils.getcwd()

Returns the directory that mpv was launched from. On error, nil, error is returned.

utils.readdir(path [, filter])

Enumerate all entries at the given path on the filesystem, and return them as array. Each entry is a directory entry (without the path). The list is unsorted (in whatever order the operating system returns it).

If the filter argument is given, it must be one of the following strings:

files

List regular files only. This excludes directories, special files (like UNIX device files or FIFOs), and dead symlinks. It includes UNIX symlinks to regular files.

dirs

List directories only, or symlinks to directories. . and .. are not included.

normal

Include the results of both files and dirs. (This is the default.)

all

List all entries, even device files, dead symlinks, FIFOs, and the . and .. entries.

On error, nil, error is returned.

utils.split_path(path)

Split a path into directory component and filename component, and return them. The first return value is always the directory. The second return value is the trailing part of the path, the directory entry.

utils.join_path(p1, p2)

Return the concatenation of the 2 paths. Tries to be clever. For example, if `p2 is an absolute path, p2 is returned without change.

utils.subprocess(t)

Runs an external process and waits until it exits. Returns process status and the captured output.

The parameter t is a table. The function reads the following entries:

args

Array of strings. The first array entry is the executable. This can be either an absolute path, or a filename with no path components, in which case the PATH environment variable is used to resolve the executable. The other array elements are passed as command line arguments.

cancellable

Optional. If set to true (default), then if the user stops playback or goes to the next file while the process is running, the process will be killed.

max_size

Optional. The maximum size in bytes of the data that can be captured from stdout. (Default: 16 MB.)

The function returns a table as result with the following entries:

status

The raw exit status of the process. It will be negative on error.

stdout

Captured output stream as string, limited to max_size.

error

nil on success. The string killed if the process was terminated in an unusual way. The string init if the process could not be started.

On Windows, killed is only returned when the process has been killed by mpv as a result of cancellable being set to true.

killed_by_us

Set to true if the process has been killed by mpv as a result of cancellable being set to true.

utils.subprocess_detached(t)

Runs an external process and detaches it from mpv's control.

The parameter t is a table. The function reads the following entries:

args

Array of strings of the same semantics as the args used in the subprocess function.

The function returns nil.

utils.parse_json(str [, trail])

Parses the given string argument as JSON, and returns it as a Lua table. On error, returns nil, error. (Currently, error is just a string reading error, because there is no fine-grained error reporting of any kind.)

The returned value uses similar conventions as mp.get_property_native() to distinguish empty objects and arrays.

If the trail parameter is true (or any value equal to true), then trailing non-whitespace text is tolerated by the function, and the trailing text is returned as 3rd return value. (The 3rd return value is always there, but with trail set, no error is raised.)

utils.format_json(v)

Format the given Lua table (or value) as a JSON string and return it. On error, returns nil, error. (Errors usually only happen on value types incompatible with JSON.)

The argument value uses similar conventions as mp.set_property_native() to distinguish empty objects and arrays.

utils.to_string(v)

Turn the given value into a string. Formats tables and their contents. This doesn't do anything special; it is only needed because Lua is terrible.

Events

Events are notifications from player core to scripts. You can register an event handler with mp.register_event.

Note that all scripts (and other parts of the player) receive events equally, and there's no such thing as blocking other scripts from receiving events.

Example:

function my_fn(event)
    print("start of playback!")
end

mp.register_event("file-loaded", my_fn)

List of events

start-file

Happens right before a new file is loaded. When you receive this, the player is loading the file (or possibly already done with it).

end-file

Happens after a file was unloaded. Typically, the player will load the next file right away, or quit if this was the last file.

The event has the reason field, which takes one of these values:

eof

The file has ended. This can (but doesn't have to) include incomplete files or broken network connections under circumstances.

stop

Playback was ended by a command.

quit

Playback was ended by sending the quit command.

error

An error happened. In this case, an error field is present with the error string.

redirect

Happens with playlists and similar. Details see MPV_END_FILE_REASON_REDIRECT in the C API.

unknown

Unknown. Normally doesn't happen, unless the Lua API is out of sync with the C API. (Likewise, it could happen that your script gets reason strings that did not exist yet at the time your script was written.)

file-loaded

Happens after a file was loaded and begins playback.

seek

Happens on seeking. (This might include cases when the player seeks internally, even without user interaction. This includes e.g. segment changes when playing ordered chapters Matroska files.)

playback-restart

Start of playback after seek or after file was loaded.

idle

Idle mode is entered. This happens when playback ended, and the player was started with --idle or --force-window. This mode is implicitly ended when the start-file or shutdown events happen.

tick

Called after a video frame was displayed. This is a hack, and you should avoid using it. Use timers instead and maybe watch pausing/unpausing events to avoid wasting CPU when the player is paused.

shutdown

Sent when the player quits, and the script should terminate. Normally handled automatically. See Details on the script initialization and lifecycle.

log-message

Receives messages enabled with mp.enable_messages. The message data is contained in the table passed as first parameter to the event handler. The table contains, in addition to the default event fields, the following fields:

prefix

The module prefix, identifies the sender of the message. This is what the terminal player puts in front of the message text when using the --v option, and is also what is used for --msg-level.

level

The log level as string. See msg.log for possible log level names. Note that later versions of mpv might add new levels or remove (undocumented) existing ones.

text

The log message. The text will end with a newline character. Sometimes it can contain multiple lines.

Keep in mind that these messages are meant to be hints for humans. You should not parse them, and prefix/level/text of messages might change any time.

get-property-reply

Undocumented (not useful for Lua scripts).

set-property-reply

Undocumented (not useful for Lua scripts).

command-reply

Undocumented (not useful for Lua scripts).

client-message

Undocumented (used internally).

video-reconfig

Happens on video output or filter reconfig.

audio-reconfig

Happens on audio output or filter reconfig.

The following events also happen, but are deprecated: tracks-changed, track-switched, pause, unpause, metadata-update, chapter-change. Use mp.observe_property() instead.

Extras

This documents experimental features, or features that are "too special" to guarantee a stable interface.

mp.add_hook(type, priority, fn)

Add a hook callback for type (a string identifying a certain kind of hook). These hooks allow the player to call script functions and wait for their result (normally, the Lua scripting interface is asynchronous from the point of view of the player core). priority is an arbitrary integer that allows ordering among hooks of the same kind. Using the value 50 is recommended as neutral default value. fn is the function that will be called during execution of the hook.

See `Hooks`_ for currently existing hooks and what they do - only the hook list is interesting; handling hook execution is done by the Lua script function automatically.