client computer build meant for 4k movies but not gaming

ok for some reason my clients computer is struggling to play 4k movies on his 4k tv i want to avoid buying anymore new parts but i suspect that hes gonna need to get another graphics card. im thinking a gtx 1050ti
and getting a long enough displayport cable with an hdmi 2.0 adaptor since there seems to be a lack of 35-45 foot long hdmi 2.0 cables.

system specs:
windows 7 64bit
intel core-i5 7400 kaby lake
Patriot Viper Elite 8GB (2 x 4GB) 2133mhz
asrock h110m-dvp
amd radeon r7 350 2gbyte [no extra power connections]
650 watt power supply
he is using an old 35-45 foot hdmi cord i dont know version it is im thinking 1.0
and a cheap $15 sound card but he uses an audio switcher to switch to hdmi audio

I don't think he needs another graphics card. My concern is with the length of the cable.
Going The Distance - A Guide to Maximum Cable Lengths - Cable Chick Blog

i wouldn't be surprised but atleast i already have a gtx 1050 ti from my gaming rig so i will be able to test it though when i was doing my testing with the current setup there were no artifacts on the screen nor was the signal dropped hes currently using 64x vlc player, how to train your drogan 4k played perfectly but other movies seem to judder and lag for some reason and i know his graphics cards hdmi port is of the hdmi 1.4 standard though i have yet to find out if that can be updated via a firmware update

and then this forum is as dead as ever