Bug/Enhancement: check_sp_output hangs indefinitely on frozen FFmpeg streams

[abhiTronix]

Description

When using check_sp_output to capture output from continuous FFmpeg streams (such as live device inputs like ffmpeg -f v4l2 -i /dev/video0), the stream can occasionally freeze. Because the underlying subprocess.communicate() call lacks a timeout parameter, the Python script blocks execution indefinitely and can only be terminated manually via Ctrl+C.

Permalink to the affected code:

deffcode/deffcode/ffhelper.py

Lines 640 to 684 in 5162649

	def check_sp_output(*args: Any, **kwargs: Any) -> bytes:
	"""
	## check_sp_output
	Returns FFmpeg `stdout` output from subprocess module.
	Parameters:
	args (based on input): Non Keyword Arguments
	kwargs (based on input): Keyword Arguments
	**Returns:** A string value.
	"""
	# workaround for python bug: https://bugs.python.org/issue37380
	if platform.system() == "Windows":
	# see comment https://bugs.python.org/msg370334
	sp._cleanup = lambda: None
	# handle additional params
	retrieve_stderr = kwargs.pop("force_retrieve_stderr", False)
	# execute command in subprocess
	process = sp.Popen(
	*args,
	stdout=sp.PIPE,
	stderr=sp.DEVNULL if not (retrieve_stderr) else sp.PIPE,
	**kwargs,
	)
	# communicate and poll process
	output, stderr = process.communicate()
	retcode = process.poll()
	# handle return code
	if retcode and not (retrieve_stderr):
	logger.error("[Pipeline-Error] :: {}".format(output.decode("utf-8")))
	cmd = kwargs.get("args")
	if cmd is None:
	cmd = args[0]
	error = sp.CalledProcessError(retcode, cmd)
	error.output = output
	raise error
	# raise error if no output
	bool(output) or bool(stderr) or logger.error(
	"[Pipeline-Error] :: Pipeline failed to exact any data from command: {}!".format(
	args[0] if args else []
	)
	)
	# return output otherwise
	return stderr if retrieve_stderr and stderr else output

Issue Checklist

• I have searched open or closed issues for my problem and found nothing related or helpful.
• I have read the Documentation and found nothing related to my problem.
• I've read the Issue Guidelines and wholeheartedly agree.

Expected behaviour

The check_sp_output function should accept a timeout argument (via kwargs) to prevent indefinite hanging. If the timeout is reached, it should cleanly catch the subprocess.TimeoutExpired exception, terminate the process, flush the remaining buffer, and return the captured output without raising a CalledProcessError.

Actual behaviour

The function delegates to process.communicate() without any time limits. If the FFmpeg process stalls, Python waits forever for the process to terminate.

Steps to reproduce

1. Create a Python script that calls check_sp_output with a long-running or potentially blocking FFmpeg command (e.g., using a live input like ffmpeg -f v4l2 -i /dev/video0).
2. Interrupt or stall the FFmpeg stream (e.g., disconnect the video device / simulate a hang).
3. Observe that the Python process never returns from check_sp_output unless killed.
4. Try to pass a timeout argument to check_sp_output (currently unsupported).
5. The process should return/timeout gracefully rather than freeze indefinitely.

Terminal log output

Python Code(Optional)

DeFFcode Version

0.2.8

Python version

All

Operating System version

All

Any other Relevant Information?

This is both a bug and a possible enhancement, as resolving this will make DeFFcode more robust for handling real-time streaming inputs and non-blocking system calls.

[abhiTronix]

Fixed in commit: 210cb16