Watching the at home concert last night and I hit the record button when there was 40 mins left. But it recorded the last 60 minutes, not 40. I assume this is by design. Does this mean it is already recording as long as I don’t change the channel?
Most DVR software keeps a running buffer of the last N minutes, so that you can instant-replay or seek back a short distance. When you start recording, since it already has the recent N minutes recorded, it just starts the recording with that buffer. At least, so I presume based on your description. Not all DVR software will do that.
I think I remember this happened in the past too. Maybe the buffer is 20 minutes since that is the extra amount I got. this is ATT Uverse if anyone is curious.
Pretty easy to test. Just keep your TV on a channel for an hour and then hit the rewind button and see how far back it goes. That’s your buffer.
Using Verizon FIOS it records the last two channels – that’s how you can pause and rewind ‘live’ broadcasts.
You can measure the size of the buffer by pausing a live feed. It’ll jump back to ‘live’ signal when the buffer is full.
My DVR has a buffer of 90 minutes. If the DVR has been on for a while on the Law and Order all the time channel, and I turn on the screen at the last minute of an episode, I can either rewind to the beginning of the episode (or really, the end of the previous episode) - or hit record and get the whole episode recorded to watch later (what I can’t do is record the last half hour of the earlier episode).