import math
import numpy as np
from gnes.preprocessor.base import BaseVideoPreprocessor
from gnes.proto import gnes_pb2, array2blob, blob2array
[docs]class FrameSelectPreprocessor(BaseVideoPreprocessor):
def __init__(self,
sframes: int = 1,
*args,
**kwargs):
super().__init__(*args, **kwargs)
self.sframes = sframes
[docs] def apply(self, doc: 'gnes_pb2.Document') -> None:
super().apply(doc)
if len(doc.chunks) > 0:
for chunk in doc.chunks:
images = blob2array(chunk.blob)
if len(images) == 0:
self.logger.warning("this chunk has no frame!")
elif self.sframes == 1:
idx = [int(len(images) / 2)]
chunk.blob.CopyFrom(array2blob(images[idx]))
elif self.sframes > 0 and len(images) > self.sframes:
if len(images) >= 2 * self.sframes:
step = math.ceil(len(images) / self.sframes)
chunk.blob.CopyFrom(array2blob(images[::step]))
else:
idx = np.sort(np.random.choice(len(images), self.sframes, replace=False))
chunk.blob.CopyFrom(array2blob(images[idx]))
del images
else:
self.logger.error(
'bad document: "doc.chunks" is empty!')