Dynamic text inside video.add_text does not update

[gavin2812]

Hi all,

I'm using liquidsoap 2.1.4 and I am trying to add dynamic text to a video using this:

v = video.add_text.ffmpeg.raw.filter(
      color=0xff0000,
      x=20,
      y=500,
      size=36,
      speed=0,
      graph=graph,
      screentext,
      v)

where screentext is this:

def update_time() =
	screentext = process.read("cat /home/test/mytext.txt")
	print(screentext)
end
thread.run(every=1.,update_time)

But even though the text updates correctly in the console, it does not update on the screen. I have it hardcoded at the beginning of the script as follows:

screentext = process.read("cat /home/test/mytext.txt")

And on the screen it initially shows that correctly, but it does not update as per the timed function even though it does update in the console correctly.

Any ideas why this might be?

Thanks in advance.

[smimram]

You need a reference for this: the definition of screentext is otherwise local to the update_time function. It should thus be something like

screentext = ref("undefined")

v = video.add_text.ffmpeg.raw.filter(
      color=0xff0000,
      x=20,
      y=500,
      size=36,
      speed=0,
      graph=graph,
      {!screentext},
      v)

def update_time() =
	screentext := process.read("cat /home/test/mytext.txt")
	print(!screentext)
end
thread.run(every=1.,update_time)

[gavin2812]

Hi @smimram,
Thanks for responding.
Unfortunately that didn't work, it just outputs the word "undefined" on the screen and never changes, the text updates in console correctly, so I know the variable !screentext is updating (and therefore the update_time is working, it just as if it is not updating the variable !screentext inside the video.add_text section.
I've tried every variation of this I can think of but I just cannot get the text to update on screen.
Any further ideas? Or maybe an alternative way to do it?
Thanks in advance.

[smimram]

From the doc, you actually have to call on_change method to update the text once it has changed with this operator. You should thus further change update_time to

def update_time() =
	screentext := process.read("cat /home/test/mytext.txt")
	print(!screentext)
        v.on_change()
end

[gavin2812]

@smimram thanks for your reply. I managed to get it working, I had to move the code around a bit, but ended up getting it working.

Thanks for your help, much appreciated!