Matteo Marioni, Warren, and myself have been jointly trying to test Dexter with MACH 3. This is difficult at the moment because Teo is the one with the game but he does not have a VBI Injector board so we've tried to rig up a workaround for the time being. After analysis of the MACH 3 hardware, we've concluded that the Manchester picture number can be encoded in a visible line of the video which means that the Raspberry Pi can render it without external help. So we created a laserdisc image file and tested it out.
Early results were encouraging but not was encouraging as we'd hoped. By adjusting the voltage threshold of the picture number comparing hardware, we were able to get the game to find the picture number some of the time (maybe 50% if my understanding is right) but still find garbage the other half of the time. This is quite puzzling. I really wish Teo had an injector board!
Another problem is the target data encoded in one of the audio channels on the disc. Early tests showed that trying to parse the audio data from the Raspberry Pi were resulting in complete garbage. I can think of a few things that could be wrong: a) the audio data may be offset from where it is supposed to be on the original laserdisc (a common problem with audio capturing hardware), b) the audio voltage level output by the Raspberry Pi may be too far off from the voltage level output by the original PR-8210.
Unfortunately I have neither a MACH 3 laserdisc nor a PR-8210 player so I am unable to test the voltage level coming from the audio jack on the back of that player when the disc is playing to see what the proper range should be.
At any rate, I am going to venture a guess that getting MACH 3 to work properly with Dexter may be one of the three most challenging tasks to overcome, the other two being Star Rider and Freedom Fighter (the latter possibly being the easiest of the three).