I am a volunteer at a Heritage Railway in N.Wales and, amongst other
things, I provide electronics and software for various exhibits in the
museum. I use the Raspberry Pi to provide various video presentations,
employing the omxplayer.
I am in the process of updating an application known as the 'Runaway
Train', originally written some 4ish years ago, as it has started to
exhibit intermittent faults. This involves playing a video (at 8 times
normal speed), via two TV screens, of a narrow gauge train ride from the
view of the locomotive driver, on request, with the visitor located in a
replica footplate, in which the floor vibrates and smoke emanates.
As I learn more Python I wanted to improve the interaction with
omxplayer. In the original application I called omxplayer using Popen
__________________________________________________________________________________
omxp = Popen(['omxplayer', MOVIE_PATH])
followed by
# wait for video process to finish
omxp.wait()
__________________________________________________________________________________
Having 'graduated' to Python 3.7, I thought I would explore
subprocess.Popen, and put the code in a Class, see code below. The video
runs, but an error occurs, which I do not understand, see further below
__________________________________________________________________________________
# Import subprocess
import subprocess
from io import StringIO
class Player:
def __init__(self, path, timeout ):
self.path = path
self.timeout = timeout
def playVideo(self, filename, audio):
MOVIE_PATH = self.path + filename
if ( audio == "HDMI" ):
omxp = subprocess.Popen(['omxplayer', '-s', '-o', 'hdmi',\
MOVIE_PATH],stdin=subprocess.PIPE,stdout=subprocess.PIPE,stderr=subprocess.PIPE)
else:
# Call omxplayer - audio to Analog Port
omxp = subprocess.Popen(['omxplayer', '-s', '-o', 'local',\
MOVIE_PATH],stdin=subprocess.PIPE,stdout=subprocess.PIPE,stderr=subprocess.PIPE)
try:
out = omxp.communicate(timeout=self.timeout)
print("Try outs = ", StringIO(out))
except:
omxp.kill()
out = omxp.communicate()
print("Except outs = ", StringIO(out))
__________________________________________________________________________________
Traceback (most recent call last):
File "/home/pi/Code/TestVideo#4.py", line 31, in <module>
player.playVideo(FILE, 'HDMI')
File "/home/pi/Code/VideoPlayer.py", line 51, in playVideo
out = omxp.communicate()
File "/usr/lib/python3.5/subprocess.py", line 801, in communicate
stdout, stderr = self._communicate(input, endtime, timeout)
File "/usr/lib/python3.5/subprocess.py", line 1437, in _communicate
selector.register(self.stdout, selectors.EVENT_READ)
File "/usr/lib/python3.5/selectors.py", line 351, in register
key = super().register(fileobj, events, data)
File "/usr/lib/python3.5/selectors.py", line 237, in register
key = SelectorKey(fileobj, self._fileobj_lookup(fileobj), events, data)
File "/usr/lib/python3.5/selectors.py", line 224, in _fileobj_lookup
return _fileobj_to_fd(fileobj)
File "/usr/lib/python3.5/selectors.py", line 39, in _fileobj_to_fd
"{!r}".format(fileobj)) from None
ValueError: Invalid file object: <_io.BufferedReader name=8>
__________________________________________________________________________________
From previous discussions, where do I sit in the demographics! I
graduated from a degree, that was 95% physics with a small amount of
electronics, spent 30 years as essentially an electronics engineer,
during which time I wrote software using Fortran, Basic, Pascal (HP) and
C++, typically for embedded applications. I have been retired for 10
years, and occasionally play trains.
_______________________________________________
Tutor maillist - Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor
