Hi Penfold42, thanks for your help. I can confirm that adding amlgrabber above my existing framegrabber config, the lights now work during a movie.
"amlgrabber" :
{
"width" : 64,
"height" : 64,
"frequency_Hz" : 2.5
"priority" : 889
},
"framegrabber" :
{
"width" : 64,
"height" : 64,
"frequency_Hz" : 2.5,
"priority" : 890
},