Re: tally lights

On Thu, Mar 12, 2009 at 8:10 AM, Carl Karsten <[email protected]> wrote:
> 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.

Outside of reading the spec, type 'dvcont' with no options at the
console to get a list of AV/C commands. There is not much outside of
this list for this class of AV/C device. There is a AV/C Camera
subunit spec, but I have little experience or knowledge of it.

> 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.

I do not recall ever coming across about a command to control an
indicator light in any AV/C spec. The AV/C commands are quite high
level. Think "Web Services" level of high.

> 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'):

At work, I once bought a simple, inexpensive relay board controllable
via USB with Linux:
http://www.emx.net.au/

But the USB thumb drive with mounted light seems much more of a tidy solution.

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