When watching online, the video download speed is much slower than when downloading, how to fix it?

Question

Nginx

Hello everyone, such a problem. On the video server, when watching a movie online, the speed is very low, if you download the speed is as high as possible, but if you watch online, the video is barely loaded and you have to pause and wait until it loads more (you have to wait 20-30 minutes) what could be the problem? How to fix it? Is there any way to measure the speed of online video playback. Download speed (500kb / s is the maximum of my Internet), but online is slow, about 50-100kb / s