tally lights

tally light is primarily for the camera operators' benefit.

man dvgrab...  -nostop   Disables  sending  the  AV/C  VTR  stop  command when 
exiting  dvgrab.

Wondering what other commands are available in the protocol, and how cameras 
implement them.

The dvswitch guys are trying to figure out a cheap-n-easy way to have a light go 
on when a dv stream is being used.  (where used = stream selected in dvswitch 
video mixer, so there will always be a stream coming from the camera.)  I have a 
feeling the consumer cams that are typically used won't have anything 
appropriate for this.

Other ideas:
usb thumb drive + extension, use the 'mounted' light.

usb lamp, turn the usb power on/off, but that doesn't seem reliable (not much 
here, other than 'doesn't really work'):

(05:21:10 AM) h01ger: daven, i arrived a usb hub which can be powered on and off 
from the computer. attach leds, put it in a case, tally light done
(05:25:56 AM) p2-mate: h01ger: because USB hubs are supposed to be able to turn 
off power to usb ports but don't actually do it IME
(05:27:25 AM) h01ger: it seems most/all on-board hubs cant do it, but there 
external which can
(05:28:18 AM) p2-mate: I tried 4 external ones
(05:28:21 AM) p2-mate: none worked
(05:32:19 AM) p2-mate: on-board hubs don't do it indeed
(05:32:38 AM) p2-mate: except for 1 I found on some MIPS SoC
(05:33:49 AM) p2-mate: our USB guru claimed that certification tests actually 
don't verify if the power is turned off
(05:34:10 AM) p2-mate: which would explain why almost noone implements this 
feature correctly
(05:35:49 AM) h01ger: i ment internal wires, as that page says: CAUTION: 
Although many chips implemented this feature, many products omit the circuit of 
power control, unfortunately.

Anyone have any other ideas?

Carl K

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