I'm on Firefox x64 and couldn't see the respective video. I had to set media.mp4.enabled to False (via about: config) to see the video with the HTML5 player. As shown, here, ABP located the manifest file (http://ep.ert.gr:1935/vodedge/_defi.../20170127-politistiko-deltio.mp4/manifest.f4m) under HTML5 player. With uBlock Origin, it was Not possible. You can check for yourself. Try ABP and then try uBlock Origin with HTML5 player.