The VideoLAN Forums

Posted: **09 May 2012 19:45**

Hello all,

I am a novice, but I have been attempting to write an LUA script which will get the current video's time, subtract .0416 (roughly 1/24 of a second to simulate backing up a frame), and move the playback to the new time. For a few days I have been working at this end with no success! I do not understand quite how to get the script to run. I have also decompiled hotkeys.luac and attempted to add the F12 hotkey to this function using the sample. I thank any of you for your time and efforts to help me. Here is my code:

Code: Select all

local common = require ("common")
bindings = {
["F12] = "Previous"
}
function prevframe()  --Time altering function
	local input = vlc.object.input()
	vlc.playlist.pause()
	var.get(input,"time")
	skip_back ="time"-.0416
	vlc.var.set(input, "time", skip_back)
end

--all below taken and modified from hotkeys.luac

function action(func, delta)
  return {
    func = func,
    delta = delta or 0,
    last = 0,
    times = 0
  }
end
actions = {
["Previous"] = action(prevframe)
}
action = nil
queue = {}
function action_trigger(action)
  print("action_trigger:", tostring(action))
  local a = actions[action]
  if a then
    do
      local ok, msg = pcall(a.func)
      if not ok then
        vlc.msg.err("Error while executing action `")
      end
    end
  else
    vlc.msg.err("Key `" .. key .. "' points to unknown action ")
  end
end
function key_press(var, old, key, data)
  print("key_press:", tostring(key))
  if bindings[key] then
    action_trigger(bindings[key])
  else
    vlc.msg.err("Key `" .. key .. "' isn't bound to any action.")
  end
end
vlc.var.add_callback(vlc.object.libvlc(), "key-pressed", key_press)
while true do
  repeat
  until not vlc.misc.lock_and_wait()
end
vlc.var.del_callback(vlc.object.libvlc(), "key-pressed", key_press)

I compiled this file and put into the lua/intf folder in my VLC 2.0.1 Twoflower installation. I'm not sure if the code will even work, or if the .luac file is being recognized by VLC. Could anyone point me in the right direction? I appreciate any comments or criticism.

Rob

Posted: **10 May 2012 19:29**

I also learn Scripting VLC in Lua. So far I have learnt how to use playlist and extension script. I do not know much about interface scripts yet. I think that nobody has worked with them here yet.
So you would like to make a hotkey with "Previous frame" feature.
I can see a mistake in your code. You should assign a value to a variable and do not forget to use "vlc." with functions described in VLC Lua "README" document.

Code: Select all

   current_time = vlc.var.get(input,"time")
   skip_back = current_time - .0416
   vlc.var.set(input, "time", skip_back)

If it will not work the way you want, then try to make some extension script containing simple dialog box with "Previous frame" button instead of interface script.
You can also use non-compiled scripts with ".lua" file extension as they have been used in VLC1.

I have just realised that MiniLyrics works with VLC through custom interface script that has to be turned on in preferences first, so it starts together with VLC: viewtopic.php?f=2&t=100859#p340369

If somebody knows more about interface scripts, then please write here something about it, what they are capable of, how a custom interface can help user to customize VLC, difference with extension scripts, ...

Posted: **10 May 2012 22:19**

Something like this:

Code: Select all

-- "previous frame.lua" -- VLC Extension script
function descriptor()
	return { title = "Previous frame" }
end
function activate()
    dlg = vlc.dialog("Previous frame")
    w1 = dlg:add_text_input("25.000", 1, 1, 2, 1)
	w2 = dlg:add_button("Previous frame", click_PrevFrame, 1, 2, 1, 1)
	w3 = dlg:add_label(1/25 .. " s", 2, 2, 1, 1)
end
function deactivate()
end
function close()
    vlc.deactivate()
end
function click_PrevFrame()
	w3:set_text(1/w1:get_text() .. " s")
	local input = vlc.object.input()
	--vlc.playlist.pause()
	current_time = vlc.var.get(input,"time")
	skip_back = current_time - 1/w1:get_text()
	vlc.var.set(input, "time", skip_back)
end

Just pause playing film, set proper fps and press "Previous frame" button one time or several times. You can also make "Next frame" button or you can rather use VLC's built-in hotkey "e".

Posted: **14 May 2012 17:23**

Meredi,

Thanks for this information! I knew there must be some novice mistakes in there somewhere

. I will examine your code and links and see if I can get this working.

Posted: **13 Jun 2012 10:05**

Hi Meredi,

Did you manage to get this working? Which version for VLC does this work for? Any update or additional information would be very helpful as a quick browse of this forum shows a lot of people wish they could get this feature.

Thanks.

Posted: **14 Jun 2012 20:22**

Here is an update of previous code of "Previous frame" VLC Extension script:

Code: Select all

-- "previous frame.lua" -- VLC Extension script

function descriptor()
	return { title = "Previous frame" }
end
function activate()
	create_dialog()
end
function deactivate()
end
function close()
    vlc.deactivate()
end


function create_dialog()
    w = vlc.dialog("Previous frame")
	label_fps = w:add_label("<b>Frames Per Second</b>", 1, 1, 1, 1)
	label_1frame = w:add_label("<b>1/FPS</b>", 2, 1, 1, 1)
    w1 = w:add_text_input("25.000", 1, 2, 1, 1)
	w2 = w:add_label(1/25 .. " s", 2, 2, 1, 1)
	w3 = w:add_button("Previous frame <<", click_PrevFrame, 1, 3, 1, 1)
	w4 = w:add_button(">> Next frame ", click_NextFrame, 2, 3, 1, 1)
	w5 = w:add_html("", 1, 4, 2, 1)
	w6 = w:add_button("Clear", click_Clear, 2, 5, 1, 1)
end
function click_PrevFrame()
	Frame("Previous")
end
function click_NextFrame()
	Frame("Next")
end
function click_Clear()
	w5:set_text("")
end

function Frame(action)
	if Pause_playback() then
		w2:set_text(1/w1:get_text() .. " s")
		local input = vlc.object.input()
		--vlc.playlist.pause()
		current_time = vlc.var.get(input,"time")
		frame_duration = 1/w1:get_text()
		if action=="Previous" then
			frame_duration=-frame_duration
		end
		skip_frame = current_time + frame_duration
		w5:set_text(skip_frame.."<br />"..current_time.." "..frame_duration.."<br />"..w5:get_text())
		vlc.var.set(input, "time", skip_frame)
	end
end
function Pause_playback()
	if vlc.input.is_playing() then
		status = vlc.playlist.status()
		--w5:set_text(status.."<br />"..w5:get_text())
		if status=="playing" then
			vlc.playlist.pause()
		elseif status=="stopped" or status=="unknown" then
			return false
		end
		return true
	else
		return false
	end
end

It works quite well with AVI-XVID-MP3 format I usually work with, however it is not perfect. Could anybody test it with different formats you use and/or improve the extension? I do not know whether it is suitable for publishing on http://addons.videolan.org

Posted: **07 Aug 2012 15:25**

I know nothing about LUA but would like to use your "previous frame" code in VLC. Can you direct me to the place that describes how to accomplish this using a shortcut or actually placing it on the control panel as with the "next frame" that is already available in VLC.

Thanks!

Ben

Posted: **10 Jan 2013 23:02**

I have just polished the script as much as I could and added "Numpad 4" and "Numpad 6" hotkeys.
Here it is: VLC Extension: Previous frame

Posted: **10 Jan 2013 23:42**

Nice. Does it work well?

Posted: **10 Jan 2013 23:51**

It works quite well at least with AVI{XVID, MP3} format that I use the most.

Posted: **11 Jan 2013 00:01**

TS? MKV?

Posted: **11 Jan 2013 00:32**

If I find some TS and MKV, I will test them later. You can also try the extension out, can't you? You could run it on all 3 operating systems and share an experience as I am only on Windows XP. Thanks.

Posted: **11 Jan 2013 21:11**

I tested the extension on a short sample of TS{M2V, M1A} and MKV{AVC1, AAC}. The extension does not work well with these formats if you would like to perform split-second jumps, but it still can be used for longer backward/forward jumps. Tiny jumps work well in AVI{XVID, MP3}.

Posted: **23 Oct 2013 12:04**

Hi mederi!
Thanks for your extension, it is very useful for me. But now that I switched my OS to Windows 8, it does not work anymore. I can see the entry in the View-menu of VLC, but the window does not pop up on click. I used WindowsXP before, where it worked without problems. VLC version is 2.1.0. Could you help me?

Posted: **24 Oct 2013 13:06**

Edit the script in a text editor. Commnet out or delete two lines, 23 and 26:

Code: Select all

-- vlc.var.add_callback( vlc.object.libvlc(), "key-pressed", key_press )
-- vlc.var.del_callback( vlc.object.libvlc(), "key-pressed", key_press )

This way you eliminate custom hotkeys (Num4 & Num6) in this extension.
add_callback() is not available in VLC-2.1

Posted: **05 Nov 2013 14:58**

Yes, that helped! Thanks a lot!

Posted: **10 Nov 2014 13:39**

Coul someone please explain me how to change the hotkeys to other keys? Specifically the (,) and (.) keys. I tried changing the global variable key codes to both 33 & 34, as well as 188 & 190, because different resources had listed different key codes, - neither of which worked. I also tried remapping the (,) and (.) keys with AutoHotkey to the Numpad4 and Numpad6 keys, and while the keys were remapped correctly, these didn't work when trying to switch to the previous/next frames.

Posted: **10 Nov 2014 15:02**

Lua Hotkeys work only in VLC-2.0.x and VLC-1.1.x!
What key codes do you see in dialog box in HELP > Logger if you press "," and "." in VLC player? My computer says 44 and 46.

Posted: **11 Nov 2014 16:31**

I didn't realize, the hotkeys worked only in those versions. I have 2.1.5 installed. The logger didn't register any key presses, not just the (,) and (.).
Is it impossible to write a script with such behaviour regardless of the version?

Posted: **11 Nov 2014 22:50**

You need to disable hotkeys in the downloaded script for VLC-2.1+ (instructions are provided in one of my previous posts here). You can only use buttons in dialog window of the extension.
As a workaround you could write (and share if you want) an AutoHotkey script. You could find some hints here:
https://forum.videolan.org/viewtopic.ph ... 40#p407066
https://forum.videolan.org/viewtopic.ph ... 36#p403621

Posted: **02 Dec 2014 18:48**

Sorry for taking so long.
I wrote and AutoHotkey script that checked for and launched the Previous frame plug-in window, then activated VLC, and simulated pressing the "Previous frame" and "Next frame" buttons in the now inactive plug-in window.
While the part that checked/launched the plug-in window worked consistently when nothing was playing, it worked less consistently, when a video was playing, I suspect because the script had to find the VLC window name in a substantially longer string of the window, which included the name of the video, that was playing. I tried experimenting by adding cooldown time between actions with less than satisfactory results, and ran out of ideas on how to improve the reliability of this part of the script.
The part that simulated the button presses in the inactive plug-in worked pretty much flawlessly.
Unfortunately I was surprised to notice that the plug-in didn't work as it was supposed to, which had slipped my attention when playing with the plug-in even before writing the script. The customization of the fps jump time did not affect the action of the Previous/Next buttons, when the length of the jump was under a second. In fact, in this case, the "Previous frame" button also triggers a jump forward, and the actual jump with an fps set to 25 is under a second, but much longer than the supposed 0.04s, somewhere around 1/4 to 1/5 of a second, because with around 4-5 presses the time moves by around a second. The VLC built-in e key forward jump on the other hand works consistently. When the fps was set to 1 or under, i.e., the length of the jump was a second or above, the buttons seem to work reliably.
My guess is that there are some more incompatibilities between this script and VLC 2.1.x, not just the hotkeys that have to be disabled, to launch the plug-in window.
I use VLC 2.1.5

Posted: **27 Dec 2014 22:08**

Previous frame extension
Here is an updated version of the script, which does work in VLC 2.1.5.

I changed the hotkeys to Alt+W and Alt+E. They only work when the dialog box is focused.
There is still a problem regarding some video formats, that a backward jump shorter than 1/5 sec jumps forward. I can't figure out the reason, the code seems to be correct.
http://238.szm.com/files/previous-frame ... me-2-1.lua

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Altering "time", adding hotkeys via LUA

Altering "time", adding hotkeys via LUA

Re: Altering "time", adding hotkeys via LUA

VLC Extension: Previous frame

Re: Altering "time", adding hotkeys via LUA

Re: Altering "time", adding hotkeys via LUA

Re: Altering "time", adding hotkeys via LUA

Re: Altering "time", adding hotkeys via LUA

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Re: Altering "time", adding hotkeys via LUA

Re: Altering "time", adding hotkeys via LUA

Re: Altering "time", adding hotkeys via LUA

Re: Altering "time", adding hotkeys via LUA

Re: Altering "time", adding hotkeys via LUA

Re: Altering "time", adding hotkeys via LUA

Re: Altering "time", adding hotkeys via LUA

Re: Altering "time", adding hotkeys via LUA

Re: Altering "time", adding hotkeys via LUA

Re: Altering "time", adding hotkeys via LUA

Re: Altering "time", adding hotkeys via LUA

Re: Altering "time", adding hotkeys via LUA

Re: Altering "time", adding hotkeys via LUA

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