Update datasets.py comments (#5088)

utils/datasets.py

@@ -155,7 +155,8 @@ class _RepeatSampler(object):
             yield from iter(self.sampler)
 
 
-class LoadImages:  # for inference
+class LoadImages:
+    # YOLOv5 image/video dataloader, i.e. `python detect.py --source image.jpg/vid.mp4`
     def __init__(self, path, img_size=640, stride=32, auto=True):
         p = str(Path(path).resolve())  # os-agnostic absolute path
         if '*' in p:
@@ -237,6 +238,7 @@ class LoadImages:  # for inference
 
 
 class LoadWebcam:  # for inference
+    # YOLOv5 local webcam dataloader, i.e. `python detect.py --source 0`
     def __init__(self, pipe='0', img_size=640, stride=32):
         self.img_size = img_size
         self.stride = stride
@@ -277,7 +279,8 @@ class LoadWebcam:  # for inference
         return 0
 
 
-class LoadStreams:  # multiple IP or RTSP cameras
+class LoadStreams:
+    # YOLOv5 streamloader, i.e. `python detect.py --source 'rtsp://example.com/media.mp4'  # RTSP, RTMP, HTTP streams`
     def __init__(self, sources='streams.txt', img_size=640, stride=32, auto=True):
         self.mode = 'stream'
         self.img_size = img_size
@@ -365,7 +368,8 @@ def img2label_paths(img_paths):
     return [sb.join(x.rsplit(sa, 1)).rsplit('.', 1)[0] + '.txt' for x in img_paths]
 
 
-class LoadImagesAndLabels(Dataset):  # for training/testing
+class LoadImagesAndLabels(Dataset):
+    # YOLOv5 train_loader/val_loader, loads images and labels for training and validation
     cache_version = 0.5  # dataset labels *.cache version
 
     def __init__(self, path, img_size=640, batch_size=16, augment=False, hyp=None, rect=False, image_weights=False,
@@ -659,8 +663,7 @@ def load_image(self, i):
 
 
 def load_mosaic(self, index):
-    # loads images in a 4-mosaic
-
+    # YOLOv5 4-mosaic loader. Loads 1 image + 3 random images into a 4-image mosaic
     labels4, segments4 = [], []
     s = self.img_size
     yc, xc = [int(random.uniform(-x, 2 * s + x)) for x in self.mosaic_border]  # mosaic center x, y
@@ -717,8 +720,7 @@ def load_mosaic(self, index):
 
 
 def load_mosaic9(self, index):
-    # loads images in a 9-mosaic
-
+    # YOLOv5 9-mosaic loader. Loads 1 image + 8 random images into a 9-image mosaic
     labels9, segments9 = [], []
     s = self.img_size
     indices = [index] + random.choices(self.indices, k=8)  # 8 additional image indices