ipc.rst

JSON IPC

mpv can be controlled by external programs using the JSON-based IPC protocol. It can be enabled by specifying the path to a unix socket or a named pipe using the option --input-ipc-server, or the file descriptor number of a unix socket or a named pipe using --input-ipc-client. Clients can connect to this socket and send commands to the player or receive events from it.

Warning

This is not intended to be a secure network protocol. It is explicitly insecure: there is no authentication, no encryption, and the commands themselves are insecure too. For example, the run command is exposed, which can run arbitrary system commands. The use-case is controlling the player locally. This is not different from the MPlayer slave protocol.

Socat example

You can use the socat tool to send commands (and receive replies) from the shell. Assuming mpv was started with:

mpv file.mkv --input-ipc-server=/tmp/mpvsocket

Then you can control it using socat:

> echo '{ "command": ["get_property", "playback-time"] }' | socat - /tmp/mpvsocket
{"data":190.482000,"error":"success"}

In this case, socat copies data between stdin/stdout and the mpv socket connection.

See the --idle option how to make mpv start without exiting immediately or playing a file.

It's also possible to send input.conf style text-only commands:

> echo 'show-text ${playback-time}' | socat - /tmp/mpvsocket

But you won't get a reply over the socket. (This particular command shows the playback time on the player's OSD.)

Command Prompt example

Unfortunately, it's not as easy to test the IPC protocol on Windows, since Windows ports of socat (in Cygwin and MSYS2) don't understand named pipes. In the absence of a simple tool to send and receive from bidirectional pipes, the echo command can be used to send commands, but not receive replies from the command prompt.

Assuming mpv was started with:

mpv file.mkv --input-ipc-server=\\.\pipe\mpvsocket

You can send commands from a command prompt:

echo show-text ${playback-time} >\\.\pipe\mpvsocket

To be able to simultaneously read and write from the IPC pipe, like on Linux, it's necessary to write an external program that uses overlapped file I/O (or some wrapper like .NET's NamedPipeClientStream.)

You can open the pipe in PuTTY as "serial" device. This is not very comfortable, but gives a way to test interactively without having to write code.

Protocol

The protocol uses UTF-8-only JSON as defined by RFC-8259. Unlike standard JSON, "u" escape sequences are not allowed to construct surrogate pairs. To avoid getting conflicts, encode all text characters including and above codepoint U+0020 as UTF-8. mpv might output broken UTF-8 in corner cases (see "UTF-8" section below).

Clients can execute commands on the player by sending JSON messages of the following form:

{ "command": ["command_name", "param1", "param2", ...] }

where command_name is the name of the command to be executed, followed by a list of parameters. Parameters must be formatted as native JSON values (integers, strings, booleans, ...). Every message must be terminated with \n. Additionally, \n must not appear anywhere inside the message. In practice this means that messages should be minified before being sent to mpv.

mpv will then send back a reply indicating whether the command was run correctly, and an additional field holding the command-specific return data (it can also be null).

{ "error": "success", "data": null }

mpv will also send events to clients with JSON messages of the following form:

{ "event": "event_name" }

where event_name is the name of the event. Additional event-specific fields can also be present. See `List of events`_ for a list of all supported events.

Because events can occur at any time, it may be difficult at times to determine which response goes with which command. Commands may optionally include a request_id which, if provided in the command request, will be copied verbatim into the response. mpv does not interpret the request_id in any way; it is solely for the use of the requester. The only requirement is that the request_id field must be an integer (a number without fractional parts in the range -2^63..2^63-1). Using other types is deprecated and will currently show a warning. In the future, this will raise an error.

For example, this request:

{ "command": ["get_property", "time-pos"], "request_id": 100 }

Would generate this response:

{ "error": "success", "data": 1.468135, "request_id": 100 }

If you don't specify a request_id, command replies will set it to 0.

All commands, replies, and events are separated from each other with a line break character (\n).

If the first character (after skipping whitespace) is not {, the command will be interpreted as non-JSON text command, as they are used in input.conf (or mpv_command_string() in the client API). Additionally, lines starting with # and empty lines are ignored.

Currently, embedded 0 bytes terminate the current line, but you should not rely on this.

Data flow

Currently, the mpv-side IPC implementation does not service the socket while a command is executed and the reply is written. It is for example not possible that other events, that happened during the execution of the command, are written to the socket before the reply is written.

This might change in the future. The only guarantee is that replies to IPC messages are sent in sequence.

Also, since socket I/O is inherently asynchronous, it is possible that you read unrelated event messages from the socket, before you read the reply to the previous command you sent. In this case, these events were queued by the mpv side before it read and started processing your command message.

If the mpv-side IPC implementation switches away from blocking writes and blocking command execution, it may attempt to send events at any time.

You can also use asynchronous commands, which can return in any order, and which do not block IPC protocol interaction at all while the command is executed in the background.

Asynchronous commands

Command can be run asynchronously. This behaves exactly as with normal command execution, except that execution is not blocking. Other commands can be sent while it's executing, and command completion can be arbitrarily reordered.

The async field controls this. If present, it must be a boolean. If missing, false is assumed.

For example, this initiates an asynchronous command:

{ "command": ["screenshot"], "request_id": 123, "async": true }

And this is the completion:

{"request_id":123,"error":"success","data":null}

By design, you will not get a confirmation that the command was started. If a command is long running, sending the message will not lead to any reply until much later when the command finishes.

Some commands execute synchronously, but these will behave like asynchronous commands that finished execution immediately.

Cancellation of asynchronous commands is available in the libmpv API, but has not yet been implemented in the IPC protocol.

Commands with named arguments

If the command field is a JSON object, named arguments are expected. This is described in the C API mpv_command_node() documentation (the MPV_FORMAT_NODE_MAP case). In some cases, this may make commands more readable, while some obscure commands basically require using named arguments.

Currently, only "proper" commands (as listed by `List of Input Commands`_) support named arguments.

Commands

In addition to the commands described in `List of Input Commands`_, a few extra commands can also be used as part of the protocol:

client_name

Return the name of the client as string. This is the string ipc-N with N being an integer number.

get_time_us

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

get_property

Return the value of the given property. The value will be sent in the data field of the replay message.

Example:

{ "command": ["get_property", "volume"] }
{ "data": 50.0, "error": "success" }

get_property_string

Like get_property, but the resulting data will always be a string.

Example:

{ "command": ["get_property_string", "volume"] }
{ "data": "50.000000", "error": "success" }

set_property

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

Example:

{ "command": ["set_property", "pause", true] }
{ "error": "success" }

set_property_string

Alias for set_property. Both commands accept native values and strings.

observe_property

Watch a property for changes. If the given property is changed, then an event of type property-change will be generated

Example:

{ "command": ["observe_property", 1, "volume"] }
{ "error": "success" }
{ "event": "property-change", "id": 1, "data": 52.0, "name": "volume" }

Warning

If the connection is closed, the IPC client is destroyed internally, and the observed properties are unregistered. This happens for example when sending commands to a socket with separate socat invocations. This can make it seem like property observation does not work. You must keep the IPC connection open to make it work.

observe_property_string

Like observe_property, but the resulting data will always be a string.

Example:

{ "command": ["observe_property_string", 1, "volume"] }
{ "error": "success" }
{ "event": "property-change", "id": 1, "data": "52.000000", "name": "volume" }

unobserve_property

Undo observe_property or observe_property_string. This requires the numeric id passed to the observed command as argument.

Example:

{ "command": ["unobserve_property", 1] }
{ "error": "success" }

request_log_messages

Enable output of mpv log messages. They will be received as events. The parameter to this command is the log-level (see mpv_request_log_messages C API function).

Log message output is meant for humans only (mostly for debugging). Attempting to retrieve information by parsing these messages will just lead to breakages with future mpv releases. Instead, make a feature request, and ask for a proper event that returns the information you need.

enable_event, disable_event

Enables or disables the named event. Mirrors the mpv_request_event C API function. If the string all is used instead of an event name, all events are enabled or disabled.

By default, most events are enabled, and there is not much use for this command.

get_version

Returns the client API version the C API of the remote mpv instance provides.

See also: DOCS/client-api-changes.rst.

UTF-8

Normally, all strings are in UTF-8. Sometimes it can happen that strings are in some broken encoding (often happens with file tags and such, and filenames on many Unixes are not required to be in UTF-8 either). This means that mpv sometimes sends invalid JSON. If that is a problem for the client application's parser, it should filter the raw data for invalid UTF-8 sequences and perform the desired replacement, before feeding the data to its JSON parser.

mpv will not attempt to construct invalid UTF-8 with broken "u" escape sequences. This includes surrogate pairs.

JSON extensions

The following non-standard extensions are supported:

• a list or object item can have a trailing ","
• object syntax accepts "=" in addition of ":"
• object keys can be unquoted, if they start with a character in "A-Za-z_" and contain only characters in "A-Za-z0-9_"
• byte escapes with "xAB" are allowed (with AB being a 2 digit hex number)

Example:

{ objkey = "value\x0A" }

Is equivalent to:

{ "objkey": "value\n" }

Alternative ways of starting clients

You can create an anonymous IPC connection without having to set --input-ipc-server. This is achieved through a mpv pseudo scripting backend that starts processes.

You can put .run file extension in the mpv scripts directory in its config directory (see the `FILES`_ section for details), or load them through other means (see `Script location`_). These scripts are simply executed with the OS native mechanism (as if you ran them in the shell). They must have a proper shebang and have the executable bit set.

When executed, a socket (the IPC connection) is passed to them through file descriptor inheritance. The file descriptor is indicated as the special command line argument --mpv-ipc-fd=N, where N is the numeric file descriptor.

The rest is the same as with a normal --input-ipc-server IPC connection. mpv does not attempt to observe or other interact with the started script process.

This does not work in Windows yet.