Genlock Vs. Timecode Synch at DVinfo.net

Jeremy Jacobs · September 26th, 2005, 01:24 PM

Hello,

A discussion has been circulating through the office regarding upcoming
cameras and their feature of genlock. My question which has gone unanswered
is if there is really any practical benefit to having genlock instead of just
timecode synch.

After questioning a few individuals, I have not heard one applicable situation
for the utilization of genlock where timecode sync would not work just as well.

Thanks,

Jeremy.

Jeff Donald · September 26th, 2005, 01:50 PM

In a true production environment you would want all the VTR's, cameras, etc. in a suite to have the same sync (genlock) but not the same timecode.

Glenn Chan · September 26th, 2005, 02:31 PM

If you are using an analog switcher, genlock is necessary to prevent hue shifts when dissolving or cutting between inputs.

Some switchers nowadays have frame stores, which deals with the synchronization problem. The discontinued Videonics MX1 way back when had this, and was only $1000.

I've never dealt with timecode sync, so wouldn't know if that would do the same thing as genlock.

A. J. deLange · September 26th, 2005, 02:38 PM

I have no experience with studio equipment. Keep that in mind when reading this reply. The genlock signal gives you the sync pedestal including color burst. A device receiving this sync has only to lock it's horizontal master oscillator directly to the horizontal line rate and its color subcarrier oscillator directly to the color burst i.e. the phase detectors operate at the frequency being synthesized). With time code lock neither of these signals is directly available so the local oscillators must be scaled to some lower frequency and the phase comparisons done with the time code carrier (to be honest, I've never looked at LTC on a 'scope but it has the definite aroma of IRIG B about it i.e. amplitude modulated audio frequency carrier). This scheme requires higher effective loop bandwidths and thus would not give as tight a lock as with the black burst signal. In support of this way of thinking I note that some audio equipment locked to blackburst promises sample accurate timing. Resolved to time code it does not. While time code based sync is doubtless good enough for cutting between scenes from cameras locked with it in post it may not be good enough for switching or fading between cameras in real time.

Jeremy Jacobs · September 26th, 2005, 05:27 PM

Thanks for the replies!

September 26th, 2005, 01:24 PM	#1
Jeremy Jacobs New Boot Join Date: Sep 2004 Location: West Lafayette, IN Posts: 12	Genlock Vs. Timecode Synch Hello, A discussion has been circulating through the office regarding upcoming cameras and their feature of genlock. My question which has gone unanswered is if there is really any practical benefit to having genlock instead of just timecode synch. After questioning a few individuals, I have not heard one applicable situation for the utilization of genlock where timecode sync would not work just as well. Thanks, Jeremy. __________________ http://www.reel-stream.com

September 26th, 2005, 01:50 PM	#2
Jeff Donald Warden Join Date: Mar 2002 Location: Clearwater, FL Posts: 8,287	In a true production environment you would want all the VTR's, cameras, etc. in a suite to have the same sync (genlock) but not the same timecode. __________________ Jeff Donald Carpe Diem Search DVinfo.net for quick answers \| Where to Buy? From the best in the business: DVinfo.net sponsors

September 26th, 2005, 05:27 PM	#5
Jeremy Jacobs New Boot Join Date: Sep 2004 Location: West Lafayette, IN Posts: 12	Thanks for the replies! __________________ http://www.reel-stream.com

September 26th, 2005, 02:31 PM	#3
Glenn Chan Inner Circle Join Date: Jun 2003 Location: Toronto, Canada Posts: 4,750	If you are using an analog switcher, genlock is necessary to prevent hue shifts when dissolving or cutting between inputs. Some switchers nowadays have frame stores, which deals with the synchronization problem. The discontinued Videonics MX1 way back when had this, and was only $1000. I've never dealt with timecode sync, so wouldn't know if that would do the same thing as genlock.

September 26th, 2005, 02:38 PM	#4
A. J. deLange Major Player Join Date: Jun 2004 Location: McLean, VA United States Posts: 749	I have no experience with studio equipment. Keep that in mind when reading this reply. The genlock signal gives you the sync pedestal including color burst. A device receiving this sync has only to lock it's horizontal master oscillator directly to the horizontal line rate and its color subcarrier oscillator directly to the color burst i.e. the phase detectors operate at the frequency being synthesized). With time code lock neither of these signals is directly available so the local oscillators must be scaled to some lower frequency and the phase comparisons done with the time code carrier (to be honest, I've never looked at LTC on a 'scope but it has the definite aroma of IRIG B about it i.e. amplitude modulated audio frequency carrier). This scheme requires higher effective loop bandwidths and thus would not give as tight a lock as with the black burst signal. In support of this way of thinking I note that some audio equipment locked to blackburst promises sample accurate timing. Resolved to time code it does not. While time code based sync is doubtless good enough for cutting between scenes from cameras locked with it in post it may not be good enough for switching or fading between cameras in real time.