ffmpeg version query (#4254)

* string manipulation for ffmpeg version retrieval

* ffmpeg version 4.2 control

* commenting solution

* removing all escapes for spaces
Co-authored-by: Vincent Moens <vmoens@fb.com>

setup.py

 import os
 import io
+import re
 import sys
 from setuptools import setup, find_packages
 from pkg_resources import parse_version, get_distribution, DistributionNotFound
@@ -350,10 +351,10 @@ def get_extensions():
     has_ffmpeg = ffmpeg_exe is not None
     if has_ffmpeg:
         try:
-            ffmpeg_version = subprocess.run(
-                'ffmpeg -version | head -n1', shell=True,
-                stdout=subprocess.PIPE).stdout.decode('utf-8')
-            ffmpeg_version = ffmpeg_version.split('version')[-1].split()[0]
+            # this splits on both dots and spaces as the output format differs across versions / platforms
+            ffmpeg_version_str = str(subprocess.check_output(["ffmpeg", "-version"]))
+            ffmpeg_version = re.split(r"ffmpeg version |\.| |-", ffmpeg_version_str)[1:3]
+            ffmpeg_version = ".".join(ffmpeg_version)
             if StrictVersion(ffmpeg_version) >= StrictVersion('4.3'):
                 print(f'ffmpeg {ffmpeg_version} not supported yet, please use ffmpeg 4.2.')
                 has_ffmpeg = False