PNG export sudden slow down

[vertexgamer]

I encountered a big slowdown when exporting pngs using inference_video.py. The export process starts fast (30it/s) but after a few hundreds of frames it slow down to (6it/s). No gpu, cpu, disk or memory bottlenecks are observed. Trying adding [cv2.IMWRITE_PNG_COMPRESSION, 0] to cv2.imwrite('vid_out/{:0>7d}.png'.format(cnt), item[:, :, ::-1]) as cv2.imwrite('vid_out/{:0>7d}.png'.format(cnt), item[:, :, ::-1], [cv2.IMWRITE_PNG_COMPRESSION, 0]) barely made a difference. I'm not experienced with python and opencv, my goal is to export lossless content.