DVD player "Eject" delay: what's taking so long?

August 3, 2016 12:12 PM

With a typical DVD player, after you hit the "Eject" button it takes a few seconds before the eject starts. How can it possibly take this long for such a simple operation? What is the machine doing during those few seconds?
posted by Mechitar to Technology (7 answers total)

I'm guessing it waiting until the disc stops spinning
posted by littlesq at 12:15 PM on August 3, 2016 [1 favorite]

Response by poster: But the delay happens even if there is no disc in the machine when you hit Eject.
posted by Mechitar at 12:20 PM on August 3, 2016 [1 favorite]

Maybe the machine has no way to know if there's a disc or not. The player has to assume that there is a disc?
posted by gregr at 12:27 PM on August 3, 2016

I'm just wildly speculating here, but it could be that it was designed this way to parallel the expectations of ejecting a VHS tape, which usually took several seconds as it disengaged from the VCR heads.
If the DVD came out too fast, maybe early market research showed that people were too taken aback.
posted by jozxyqk at 12:28 PM on August 3, 2016

It's much simpler and fail-safe to design a machine that always opens the drawer the same way than to design one that opens the drawer one way if there's a disc in, and another way if there's not. What if the sensor that detects the disc fails and the spindle is lowered before the disc stops spinning? Scratched disc is whut.
posted by kindall at 12:29 PM on August 3, 2016

Best answer: I can't say every DVD player works this way, but ones I've pulled apart do not have a bunch of distinct motors: motion of the tray, positioning of the laser, etc, are handled by a bunch of cogs and levers, which must get in to a "eject disk" position for the drawer to open; likewise when it closes it must do the same for its "loading" position.

Inside the DVD player, the disk doesn't sit in the round 'groove' in the tray while it's playing -- it gets lifted out of the tray a little by the motor assembly, which sticks up through that open space in the middle of the tray. Otherwise you'd get a lot of scratches while playing disks; it doesn't touch the tray while it's spinning, it's up a little bit.

The lack of complexity means that, even if there's not a disk in the machine, that motor is sticking up through the center of the tray whenever the drive is closed, because that's how the levers and gears move everything into place.

So, the open mechanism always has to go through a system by which it's lowering the motor out of the center of the tray so that it can open, and that's not a fast movement, before the tray can push out.

Note that the 'manual' method of opening a CDROM on the PC involved pushing a stretched-out paperclip in a hole, forcing the mechanism to move, rather than just grabbing the tray and wrenching it outward -- the gears and stuff work in a particular way, and have to move through all their steps to open or close, one part doesn't just move independently.
posted by AzraelBrown at 12:45 PM on August 3, 2016 [21 favorites]

Inside the DVD player, the disk doesn't sit in the round 'groove' in the tray while it's playing -- it gets lifted out of the tray a little by the motor assembly, which sticks up through that open space in the middle of the tray. Otherwise you'd get a lot of scratches while playing disks; it doesn't touch the tray while it's spinning, it's up a little bit.

For an illustration of this, here's a video explaining the innards of a DVD drive. He talks a bit about how the spinner head has to move out of the way to insert or remove a disc at the 5:45 mark. However, it's not clear to me what mechanism actually causes this movement.
posted by Johnny Assay at 2:06 PM on August 3, 2016