From 1d5ca7ababbd4a06ac97dca32a7c2c8dda293a76 Mon Sep 17 00:00:00 2001
From: Zhicheng Yan <zyan3@fb.com>
Date: Thu, 3 Dec 2020 01:40:41 -0800
Subject: [PATCH] expose _multiprocessing_context in VideoClips class

Summary:
There are issues with multiprocessing, custom __getstate__ with Tensors and forkserver.

See details in PR below

- https://github.com/pytorch/pytorch/issues/32351

To temporarily mitigate it, expose the `_multiprocessing_context` argument.

Differential Revision: D24644136

fbshipit-source-id: ae786f363f5406d268770aa83cd9d86395194ee6
---
 torchvision/datasets/video_utils.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/torchvision/datasets/video_utils.py b/torchvision/datasets/video_utils.py
index d743cc49b13..9cb97503509 100644
--- a/torchvision/datasets/video_utils.py
+++ b/torchvision/datasets/video_utils.py
@@ -101,6 +101,7 @@ def __init__(
         _video_max_dimension=0,
         _audio_samples=0,
         _audio_channels=0,
+        _multiprocessing_context=None,
     ):
 
         self.video_paths = video_paths
@@ -114,6 +115,8 @@ def __init__(
         self._audio_samples = _audio_samples
         self._audio_channels = _audio_channels
 
+        self._multiprocessing_context = _multiprocessing_context
+
         if _precomputed_metadata is None:
             self._compute_frame_pts()
         else:
@@ -136,6 +139,7 @@ def _compute_frame_pts(self):
             batch_size=16,
             num_workers=self.num_workers,
             collate_fn=self._collate_fn,
+            multiprocessing_context=self._multiprocessing_context,
         )
 
         with tqdm(total=len(dl)) as pbar: