Add lua script

switch-both-audio.lua

@@ -0,0 +1,63 @@
+--[[
+
+An mpv script that allows switching between playing one or two audio tracks simultaneously upon file load or with a hotkey.
+
+Note that the file must have exactly two audio tracks for this script to activate, otherwise the file will be ignored.
+This script overrides user defiend `lavfi-complex` behavior.
+
+To set a keybind, add `{key} script-message switch-both-audio` line to your `input.conf` e.g:
+
+`n script-message switch-both-audio`
+
+To switch the default state to "on" upon opening a file, create `switch_both_audio.conf` file in `portable_config/script-opts` directory
+and add `enabled_on_start=yes` line to it.
+
+--]]
+
+require 'mp.options'
+local mp = require 'mp'
+local state = 'off'
+local options = {
+    enabled_on_start = false,
+}
+read_options(options,nil)
+
+local function switch_on()
+    mp.set_property('lavfi-complex', '[aid1] [aid2] amix [ao]')
+    mp.set_property('aid','no')
+    state = 'on'
+end
+
+local function switch_off()
+    mp.set_property('lavfi-complex', '')
+    mp.set_property_number('aid', 1)
+    state = 'off'
+end
+
+local function switch_state()
+    if state == 'off' then
+        switch_on()
+    elseif state == 'on' then
+        switch_off()
+    end
+end
+
+local function on_load()
+    mp.unregister_script_message('switch-both-audio') -- prevent errors in mixed playlists by always disabling first
+    local tracks_num = 0
+    for _, track in pairs(mp.get_property_native('track-list')) do
+        if track.type == 'audio' then
+            tracks_num = tracks_num + 1
+        end
+    end
+
+    if tracks_num == 2 then
+        if options.enabled_on_start then
+            switch_on()
+        end
+        mp.register_script_message('switch-both-audio', switch_state)
+    end
+end
+
+mp.register_event('start-file', switch_off) -- prevent errors in mixed playlists by always disabling first
+mp.register_event('file-loaded', on_load)