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Re: [Debconf-video] Goals, wishes and suggestions for Debconf8.

On Sun, 2007-06-24 at 07:15 +0100, Tore Sinding Bekkedal wrote:
> > > " a lamp on the camera which says whether or not the cam's on "
> > I have a pic programmed to do this, when faced with different characters
> > at a serial port. 
> As we've discussed on IRC, I myself don't see this as the right
> solution. The use of a PIC is needlessly complicated, it introduces
> cabling requirements (although the cabling requirements to make RS-232
> frames transmit correctly admittedly aren't stringent), there could be
> serial port problems, you can only run one camera per serial port,
> many machines nowadays dont even have serial ports..

> I suggest using a single I/O line off the parallel port, as it can be
> programmed to act as an 8-bit general-purpose TTL-level output.

Many machines don't have parallel ports either.

I made a half-serious suggestion to Dave that the simplest way to attach
a tally light would be to cannibalise a USB keyboard.  (I believe all
the lock lights are programmable.)  But that is sick.

As I said on IRC, Cypress has cheap microcontrollers[1],[2] with
hardware USB and flash, but programming them may be difficult without a
fairly expensive development kit[3].  However there is a fair amount of
documentation on their web site and the only critical thing missing is
the low-level flash programming protocol needed initially.
(Reprogramming can be done under firmware control[4].)  It might be
worth asking for documentation of that.

[1] http://www.cypress.com/portal/server.pt?space=CommunityPage&control=SetCommunity&CommunityID=209&PageID=259&fid=16&rpn=CY7C638xx&ref=pfm
[2] http://www.arrownac.com/aws/pg_webc/0,4513,,00.html?application=SEARCH&event=1000&search_criteria=match_begins_with&search_token=CY7C638
[3] http://www.onfulfillment.com/cypressstore/Product.aspx?d=46&p=783&sid=205
[4] http://www.cypress.com/portal/server.pt?space=CommunityPage&control=SetCommunity&CommunityID=285&PageID=552&r_folder=Application%20Notes&r_title=AN6075&ref=prt

> > However, tally lights go further than this; we should have preview (pvw) and
> > programme "monitors" in dvswitch. When a camera is cut to a pvw monitor,
> > the tally light should show green or amber; when the camera is cut to
> > transmission (Tx); the tally light should be red. 
> So, this is like A/B bus on the Helsinki video switch? Where one would
> select a source for bus A, and a source for bus B, and switch between
> them? The source for the inactive bus is the pvw source?

It also means the cam-op has advance warning.

> I'm not sure how useful this is for now. IMAO, buses only really make
> sense if you're fading between the sources or making other
> transitions. If you're just cutting between them, I don't see any
> point at all... or am I wrong on this?

We would like picture-in-picture.  And maybe rapid fades.

> > However, talkback is more important, as there have been several cases
> > where a camera operator has not been able to produce a useful shot; and
> > some direction would've been useful.
> I agree. In essence, tally lights would be only a very primitive talkback system.
> > We should be able to organise the talkback with asterisk next year
> so it should be fine.
> Are you sure the added complexity of Asterisk is worth the
> out-of-the-boxed-ness? It seems to be a very large system, with
> transcoders and CPU-intensive things... Considering we'll have gigabit
> between the machines, we could just write some near-zero-latency
> program which will push 48KHz 16-bit PCM directly from the ADC of the
> dvswitch box to the camop boxen... return comms could be largely
> accomplished with hand gestures - having camops talking during a talk
> is probably not the best thing.

I would actually like to have talkback supported in dvswitch.  It would
need to mix talkback with monitoring in some way.  But I know very
little about the audio processing necessary to do this, and the latency
between capture at the camera and processing in dvswitch could be a


Ben Hutchings
compatible: Gracefully accepts erroneous data from any source

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