How to record the panda app screen as avi using ffmpeg

record_panda_screen.py

import subprocess, sys
from direct.showbase.ShowBase import ShowBase
from panda3d.core import ClockObject


cmdstring = ('ffmpeg.exe', # put it in the same dir
            '-y',         # overwrite the file w/o warning
            '-r', '%f' % 30.0, # frame rate of encoded video
            '-an',       # no audio
            '-analyzeduration', '0',  # skip auto codec analysis
            # input params
            '-s', '800x600', # default panda window size
            '-f', 'rawvideo',   # RamImage buffer is raw buffer
            '-pix_fmt', 'rgba', # format of panda texure RamImage buffer
            '-i', '-',  # this means a pipe
            # output params
            # '-vtag', 'xvid', 
            '-vcodec', 'mpeg4',
            'test.avi')
        
p = subprocess.Popen(
            cmdstring, 
            stdin=subprocess.PIPE,
            bufsize=-1, 
            shell=False,
            )

class App(ShowBase):
    def __init__(self):
        ShowBase.__init__(self)

        self.enclosure = loader.loadModel("models/enclosure/enclosure.egg")
        self.enclosure.reparentTo(render)

        self.accept("escape", self.OnQuit)  # Escape quits
        
        fps = 30.0
        globalClock = ClockObject.getGlobalClock()
        globalClock.setMode(ClockObject.MNonRealTime)
        globalClock.setDt(1.0/float(fps))
        t = taskMgr.add(self.updateTask, "ffmpegTask")
        t.setUponDeath(lambda state: globalClock.setMode(ClockObject.MNormal))
    
    def OnQuit(self):
        p.stdin.close() # close the pipe so that ffmpeg will clsoe the avi file properly
        sys.exit() # finally exits.

    def updateTask(self, task):
        # https://www.panda3d.org/reference/1.9.0/python/panda3d.core.GraphicsOutput#a340026249c6d0c504da743305c7db94a
        tex = base.win.getScreenshot() # this gives you a texture object
        buf = tex.getRamImage().getData() # 800*600*4 = 1920000
        p.stdin.write(buf) # pass it to ffmpeg as text buffer
        return task.cont

app = App()
base.run() # start panda loop