My question won't make any difference to the end user, but do you have a way of detecting that the buffer is dumped when you START a recording as opposed to when the recording switches to Live?
Good question, though admittedly it wouldn't make a difference to us as end users... and I don't know the answer or how to find out. I supposed it could be buffering in the background until you go to live viewing... but my assumption for it being the other way around (i.e. no buffering during playback) is because of the limited number of tuners.
At any given time, on a ViP622/722 anyway, there are 3 tuners available. Two satellite and one OTA... you can record on all three and watch something pre-recorded. Or you can record on one and watch the other two in PiP (assuming single mode operation) and both are buffered... or you can record on 2 tuners and the one remaining one is buffered.
What never happens, though, is all three being buffered. Never more than 2 tuners (either both SAT or one SAT and the OTA) are buffered at the same time even though there are 3 total tuners and recording simultaneously from all 3 is possible.
IF the tuners continued to buffer during playback and only dumped after going to live viewing, then the receiver would have to make unique choices when all 3 tuners are being used to record so I'm not sure how it would decide what to buffer + that would imply an ability to track 5 total streams at the same time, which I'm not sure it can handle + the ability to playback prerecorded at the same time!
So my assumption, that it dumps when you start playback and doesn't start buffering again until you switch back to live is one that creates the least headache for the firmware programmers and is less taxing on the hardware.
Who knows, but that's sort of where I made the leap to conclusion that I've made.