Video lagging issue with two NVS 810 GPU having mosiac of 9600x3240 resolution

I have two NVS 810 GPU attached in motherboard.Connected 15 display with 2 NVS 810 GPU port.Also one Capture Input card(Yuantech) attached with the motherboard.

Created Mosiac of 3x5 for 15 display(@1920x1080 resolution per display) with total resolution of 9600x3240.

Issues(Actual Result):-

1.Whenever I play any full HD video over 9600x3240 resolution Display Wall through VLC player using Catured devices media (i.e yuantech input catured card),Video lags in VLC player.Means video doesn’t play smoothly at their native fps.
2.Even I played same full hd video through yuantech input card player,but still video lags over 9600x3240 resolution Display Wall.
3.But When I play any full HD video over 5760x3240(3x3 mosiac@1920x1080) resolution Display Wall through VLC player using Catured devices media (i.e yuantech input catured card),Video plays smoothly without any lag at their native fps.(Same case with yuantech input card player also)

Expected Result:-
Playing any Full hd video through VLC player using using Catured devices media (i.e yuantech input catured card)should not lag over 9600x3240 resolution Display.Video should play at their native fps

Note:-
Kindly suggest the solution for how to fix the above issues