如何在 python 中运行 ffmpeg 命令； 代码？

Question

i'd like to run this command

for /R %f IN (/*.mp4) DO ffmpeg -i "%f" -f wav -bitexact -acodec pcm_s16le -ar 22050 -ac 1 %~nf.wav

inside this script, like this:

import os
from datetime import date

today = date.today()
today = today.strftime('%m-%d-%Y')
dir_name = f"C:/Users/lucan/Automatically/{today}/"

def extract(user):
  test = os.listdir(dir_name)
  command = "for /R %f IN (/*.mp4) DO ffmpeg -i "%f" -f wav -bitexact -acodec pcm_s16le -ar 22050 -ac 1 %~nf.wav"
  os.system(command)
  for item in test:
    if item.endswith(".wav"):
      os.remove(os.path.join(dir_name, item))


extract("businessbarista")

when i do so this is the error message I get:

command = "for /R %f IN (/*.mp4) DO ffmpeg -i "%f" -f wav -bitexact -acodec pcm_s16le -ar 22050 -ac 1 %~nf.wav" TypeError: must be real number, not str

the command runs fine in command prompt, but not in powershell. can you help me figure out what went wrong?

Answer 1

Why mix Python & batch scripts?

If I understood the batch script for loop syntax, the following should be equivalent in Python:

from glob import glob
import subprocess as sp
from os import path

# FFmpeg command (missing input & output)
cmd = ['ffmpeg','-i',None,'-f','wav','-bitexact','-acodec','pcm_s16le','-ar','22050','-ac','1']

# likely equivalent to 'for /R %f IN (/*.mp4) DO '
for input in glob("**/*.mp4",recursive=True): 
    cmd[3] = input
    output = path.splitext(input)[0] + '.wav'
    sp.run([*cmd,output])

This snippet scans the current folder and all its subfolders and lists all mp4 files in them and return the relative paths. eg, mp4\video.mp4 . Then os.path.splitext() removes the file extension to form the output file path.

Answer 2

You have " " inside " " and this makes problem.

It treats it as two strings "first" %f "second" .

You have to replace one pair of " " with ' ' - like ' " " ' or " ' ' " .

Or you have to use \ like " \" \" "

command = 'for /R %f IN (/*.mp4) DO ffmpeg -i "%f" -f wav -bitexact -acodec pcm_s16le -ar 22050 -ac 1 %~nf.wav'