Fix issue with getting frame count from webm files in ffmpeg

utilities/ffmpeg_worker.py

@@ -1,7 +1,6 @@
 #!/usr/bin/env python3
 import re
 import time
-import ffmpeg
 from utilities.render_worker import *
 
 
@@ -14,14 +13,11 @@ class FFMPEGRenderWorker(BaseRenderWorker):
         super(FFMPEGRenderWorker, self).__init__(input_path=input_path, output_path=output_path, ignore_extensions=True,
                                                  args=args)
 
-        self.total_frames = -1
-        if os.path.exists(input_path):
-            media_stats = ffmpeg.probe(input_path)
-            for stream in media_stats['streams']:
-                if stream['codec_type'] == 'video':
-                    self.total_frames = stream['nb_frames']
-                    break
-
+        stream_info = subprocess.check_output([self.renderer_path(), "-i",  # https://stackoverflow.com/a/61604105
+                                                     input_path, "-map", "0:v:0", "-c", "copy", "-f", "null", "-y",
+                                                     "/dev/null"], stderr=subprocess.STDOUT).decode('utf-8')
+        found_frames = re.findall('frame=\s*(\d+)', stream_info)
+        self.total_frames = found_frames[-1] if found_frames else '-1'
         self.frame = 0
 
         # Stats