diff --git a/generator b/generator
index 996cc5c..34cbdb2 100755
--- a/generator
+++ b/generator
@@ -24,7 +24,7 @@ from moviepy.editor import VideoFileClip
 from PIL import Image
 from click import progressbar
 from collections import namedtuple
-from multiprocessing import Pool, cpu_count
+from multiprocessing import cpu_count, Queue, Process
 import glob
 import os
 import random
@@ -45,7 +45,8 @@ def generate_video_thumbnails(args):
     output_path = args['<output>']
     parallelism = args.get('[<parallelism>]', cpu_count()*2-1)
 
-    work_units = []
+    work_queue = Queue()
+    work_units = 0
 
     if os.path.isdir(input_path):
         # Ensure output path is also directory
@@ -69,20 +70,35 @@ def generate_video_thumbnails(args):
                     output_path, os.path.basename(file_path) + ".png"
                 )
 
-                work_units.append((file_path, single_output_path,
-                                   interval, size, columns,))
+                work_queue.put((file_path, single_output_path,
+                                interval, size, columns,))
+                work_units += 1
     else:
-        work_units.append((input_path, output_path, interval, size, columns,))
+        work_queue.put((input_path, output_path, interval, size, columns,))
+        work_units += 1
 
     # Limit the number of parallel jobs if lower number of files
-    parallelism = min(int(parallelism), len(work_units))
+    parallelism = min(int(parallelism), work_units)
 
-    # Process all files in parallel
-    with Pool(parallelism) as p:
-        p.map(process_file, work_units)
+    # Start worker processes
+    processes = []
+    for i in range(parallelism):
+        p = Process(target=worker, args=(work_queue,))
+        p.start()
+        processes.append(p)
+
+    # Block until all processes complete
+    for p in processes:
+        p.join()
 
 
-def process_file(work_unit):
+def worker(queue):
+    work_unit = queue.get()
+
+    # If no work unit then quit
+    if not work_unit:
+        return
+
     input_file, output_file, interval, size, columns = work_unit
     video_file_clip = VideoFileClip(input_file)
     output_prefix = get_output_prefix()