Hello. I am trying to load a video frame by frame using imageio, but facing an weird error when num_workers > 0. This is a short snippet to reproduce the error.
from skvideo import datasets
import imageio
import torch
from torch.utils.data import Dataset, DataLoader
class VideoDataset(Dataset):
def __init__(self, video_path):
super().__init__()
self.video_reader = imageio.get_reader(video_path)
self.metadata = self.video_reader.get_meta_data()
self.nframes = self.metadata["nframes"]
def __getitem__(self, idx):
img = self.video_reader.get_data(idx)
img = torch.from_numpy(img)
return img
def __len__(self):
return self.nframes
video_path = datasets.bikes()
video_data = VideoDataset(video_path)
video_loader = DataLoader(video_data, batch_size=4, num_workers=4)
for imgs in video_loader:
print(imgs.shape)
when I try to iteratively print the shape of the loaded tensors, it gets stuck mid way and throws an error:
torch.Size([8, 272, 640, 3])
torch.Size([8, 272, 640, 3])
torch.Size([8, 272, 640, 3])
torch.Size([8, 272, 640, 3])
torch.Size([8, 272, 640, 3])
torch.Size([8, 272, 640, 3])
torch.Size([8, 272, 640, 3])
torch.Size([8, 272, 640, 3])
---------------------------------------------------------------------------
CannotReadFrameError Traceback (most recent call last)
<ipython-input-20-453bfa4da85a> in <module>()
----> 1 for imgs in video_loader:
2 print(imgs.shape)
Note that the code works fine when num_workers=0. I can’t figure out what’s going wrong.