FFMPEG和Pythons子过程 [英] FFMPEG and Pythons subprocess

问题描述

我正在尝试为 FFMPEG 写一个gui。我正在使用pythons子进程来为每个我想要的转换创建一个ffmpeg进程。这样做很好，但是我也希望获得转换的进度，无论它是否失败等。我想我可以通过访问进程的stdout来执行此操作：

I'm trying to write a gui for FFMPEG. I'm using pythons subprocess to create a ffmpeg process for every conversion I want. This works fine, but I'd also like a way to get the progress of the conversion, whether it failed or not etc. I figured I could do this by accessing the process's stdout like so:

调用 subprocess.Popen（）

# Convert - Calls FFMPEG with current settings. (in a seperate
# thread.)
def convert(self):
    # Check if options are valid
    if self.input == "" or self.output == "":
        return False

# Make the command string
ffmpegString = self.makeString()

# Try to open with these settings
try:
    self.ffmpeg = subprocess.Popen(ffmpegString, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
except OSError:
    self.error.append("OSError: ")
except ValueError:
    self.error.append("ValueError: Couldn't call FFMPEG with these parameters")

# Convert process should be running now.

并阅读 stdout ：

convert = Convert()
convert.input = "test.ogv"
convert.output = "test.mp4"
convert.output_size = (0, 0)

convert.convert()

while 1:
    print convert.ffmpeg.stdout.readline()

这是有效的，但ffmpeg的状态不显示。我假设它与ffmpeg的刷新方式有关。有没有办法访问它？

This works but, ffmpeg's status doesn't show. I'm assuming it has something to do with way ffmpeg refreshes it. Is there a way to access it?

推荐答案

我经常注意到读取标准输出（甚至是标准错误！）与子进程，由于缓冲难以打败的问题。我最喜欢的解决方案，当我需要从子进程读取这样的stdout / stderr时，是切换到使用，而不是子进程， pexpect （或在Windows上， wexpect ）。

I've often noticed problems reading standard output (or even standard error!) with subprocess, due to buffering issues that are hard to defeat. My favorite solution, when I do need to read such stdout/stderr from the subprocess, is to switch to using, instead of subprocess, pexpect (or, on Windows, wexpect).

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