Add fix-sub-timing.lua

README.rst

@@ -11,6 +11,13 @@ auto-profiles.lua
 Automatically apply profiles based on predicates written as Lua expressions. See
 file header for details.
 
+fix-sub-timing.lua
+------------------
+
+Compute the correct speed/delay of subtitles by manually synching two points in
+time. Useful for subtitles that were e.g. timed against a PAL version of the
+video, or otherwise fucked up cases.
+
 mines.lua
 ---------
 

fix-sub-timing.lua

@@ -0,0 +1,70 @@
+--[[
+How to use:
+
+The shortcut to adjust timing is set to ctrl+w by default.
+
+Edit your input.conf and bind "sub-step 1" and "sub-step -1" to two keys, e.g.:
+
+ctrl+z sub-step -1
+ctrl+x sub-step 1
+
+Start the video, and manually synchronize the first subtitle to audio (waiting
+for someone to speak and then selecting the right subtitle with ctrl+z/ctrl+x
+works best). Then hit ctrl+w to mark the first point. Go on to a later time
+where someone speaks, and synchronize the right subtitle again. Then hit ctrl+w
+again to mark this as the second point. The script will choose a sub-delay
+and sub-speed value that makes the two points you marked show the subtitles
+as you timed them when hitting the shortcut.
+
+Technically, this assumes:
+
+   sub_time = (vid_time - sub_delay) / sub_speed
+
+which is probably what mpv does internally. Using two points in time, we can
+compute the required sub_delay and sub_speed to get to the two points to display
+the 2 subtitle events at the marked times with the same delay.
+]]
+
+sub_time_1 = nil
+vid_time_1 = nil
+sub_time_2 = nil
+vid_time_2 = nil
+
+function sub_set_time()
+    local sub_delay = mp.get_property_native("sub-delay")
+    local vid_time = mp.get_property_native("playback-time")
+    local sub_speed = mp.get_property_native("sub-speed")
+    local sub_time = (vid_time - sub_delay) / sub_speed
+
+    if sub_time_1 == nil then
+        vid_time_1 = vid_time
+        sub_time_1 = sub_time
+        mp.osd_message("Mark time 1")
+        return
+    end
+
+    if sub_time_2 ~= nil then
+        sub_time_1 = sub_time_2
+        vid_time_1 = vid_time_2
+    end
+
+    if sub_time_1 == sub_time or vid_time_1 == vid_time then
+        return
+    end
+
+    sub_time_2 = sub_time
+    vid_time_2 = vid_time
+
+    -- sub_time_1 = (vid_time_1 - delay) / speed
+    -- sub_time_2 = (vid_time_2 - delay) / speed
+
+    local new_speed = (vid_time_2 - vid_time_1) / (sub_time_2 - sub_time_1)
+    local new_delay = vid_time_2 - sub_time_2 * new_speed
+
+    print("delay=" .. tostring(new_delay) .. " speed=" .. tostring(new_speed))
+
+    mp.set_property_native("sub-delay", new_delay)
+    mp.set_property_native("sub-speed", new_speed)
+end
+
+mp.add_key_binding("ctrl+w", "sub-set-time", sub_set_time)