USING EXTERNAL TIMECODE AND GENLOCK WITH THE PANASONIC VARICAM HD CAMCORDER

INTERNAL TIMECODE:

The Varicam has two, and only two, base Timecode rates, namely (1) 29.97 and (2) 30.00. And for both the 29.97 and 30.00 Timecode base rates, you also have the choice of Drop-Frame or Non Drop-Frame Timecode modes.

You get the Varicam's Timecode frequency, or base Timecode rate by default, when you set the camcorder's System Frequency. So when you select a System Frequency of 60.00Hz, you get 30.00 Timecode by default. When you select a System Frequency of 59.94Hz, you get 29.97 Timecode by default.

All the frame rates in the Varicam are a multiple of the System Frequency, be it 59.94Hz or 60.00Hz. The Timecode rate is directly related to the System Frequency. Selecting a system frequency of 59.94Hz always gives you a Timecode rate of 29.97. And selecting a system frequency of 60.00Hz always gives you a Timecode rate of 30.00. These are the only options available to you in the Varicam. If the frame rate is 29.97fps, then it is no good trying to marry this to 30.00 Timecode. Or vise versa, if the frame rate is 30fps then it is no good trying to marry this to 29.97 Timecode etc. Therefore the System Frequency is tied to the Timecode frequency, so this unworkable mismatch can never occur.

Please note that some of the older Varicam models can not be set to a System Frequency of 60.00Hz. Factory-supplied Panasonic AJ-HDC27F (real "F's"), and later Varicam models, allow a choice of System Frequency of either 59.94Hz or 60.00Hz. The older Varicam "V's" that have been upgraded to F's do not allow for this option. The upgraded camcorders have become almost "F's, but not quite in every single respect. I believe, upgraded "V's" (i.e. Panasonic AJ-HDC27V-M1) have a System Frequency set to 59.94Hz, and it is unchangeable. And it is the same with the original, unmodified "V's" (i.e. Panasonic AJ-HDC27V). In fact, the relevant menu item doesn't even exist for the "V's" (Main Menu 4 > OPTION > System Freq.).

Unlike the Sony HDW-F900 CineAlta, the Varicam does not have a physical switch on the side of the camcorder for selecting the Drop-Frame mode, or the Non-Drop-Frame mode. Instead, there is a DF/NDF "switch" in the menu structure. It is found in the VTR Main Menu Group. The name of the menu that contains this particular control is "TC/UB". There are two items in this menu, the first is called TC MODE (and the second is called UB MODE). In TC MODE, you get the two further options: DF and NDF which sets the camcorder's internal Timecode generation to run in either Drop-Frame mode, or in Non Drop-Frame mode. This is described in the Varicam "F" User's Manual ("Operating Instructions") on page # 117.

There is an anomaly in the Varicam as follows. When the System Frequency is set to 59.94Hz, and Drop-Frame mode is selected in the menus, the Varicam will run in Drop-Frame Timecode mode for all frame rates EXCEPT "24fps" and "25fps". NOTE: The Varicam always uses Non Drop-Frame Timecode when set to a frame rate of 24fps and 25fps regardless of any other settings in the camera. In other words, the Varicam will automatically switch to Non Drop-Frame mode when you select a frame rate of either 24fps or 25fps, even when you have previously set the camcorder to operate in Drop-Frame mode in the menu structure. These rates are effectively 23.976 frames per second (for "24p"), or 24.975 frames per second (for "25p").

TIP: You can make life easy for yourself if you always use Non-Drop Frame Timecode. In the menu structure, namely VTR Main Menu > TC/UB > TC MODE > set this to "NDF" and leave it there. Things are easier to keep track of this way, and you always know where you stand. For example, if you had this menu set to "DF", then you might flip back and forth from Drop-Frame mode to Non- Drop-Frame mode depending on your frame rate setting. And this flip-flopping would be invisible to you, unless you are paying strict attention to all the relevant settings. You could easily get caught out when sending external timecode (an example is described below). Of course, sometimes Drop Frame may be legitimately called for (albeit, infrequently), and then you need to know how to deal with it in the correct manner.

EXTERNAL TIMECODE:

The Varicam gives you no indication whatsoever if it is working in Drop-Frame Timecode mode (DF) or Non Drop-Frame Timecode mode (NDF). However, when sending external Timecode to the Varicam, it is absolutely imperative that you correctly ascertain if the camcorder is working in DF or NDF mode. Both the Timecode base rate (base frequency), and also the DF or NDF mode, must match perfectly.

The way external Timecode works in the Varicam, is really a momentary jamming process. The external code jams the cadence of numbers to match each other in the Varicam's internal Timecode generator on the "whole seconds" i.e. HH:MM:SS:00 (or 00 frames). After it jams, it ignores the external code and continues to self-generate code internally (....until the external Timecode cable is re-plugged again, which initiates another momentary jamming process). After it jams to the external Timecode source, then Trilevel sync keeps everything in step from that moment onwards? Note that it is really the Varicam's internal Timecode generator that is laying down the final Timecode to tape.

Cross jamming between dissimilar Timecode bases (or frequencies) like, 23.976 jammed to 29.97, is not officially recognized or acknowledged by Panasonic, but I'm told it can be done (....although I couldn't get it to work myself).

If the Varicam's internal Timecode generator is set to deliver Drop-Frame Timecode, and you want to send the Varicam external Timecode from an external Timecode generator, then you must feed it with Drop-Frame Timecode from the external source! Everything must match internally and externally. Similarly, if the Varicam is set up for Non Drop-Frame Timecode mode internally, then you must feed it with Non Drop-Frame Timecode from the external source! If you don't respect this requirement, then periodic glitches will occur with resulting image instability. By the same token, when the Varicam is set to a frame rate of "24fps" and "25fps", then you must ALWAYS feed it Non Drop-Frame Timecode from any external source (no exceptions).

It is generally recommended that you use Non Drop-Frame Timecode exclusively, unless it is absolutely necessary to do otherwise for the particular work flow of your production. Exceptions to this rule might be broadcast applications like the live telecast of a sporting event, for example. Drop-Frame is really only applicable (or has any real usefulness) to television broadcasters. It has no value on the production, or post production, side of the equation. On the contrary ........ it can lead to annoying (indeed, often insidious) technical problems. Rule of thumb on most HD sets is to use Non Drop-Frame Timecode exclusively (.......unless there is an extremely good reason to do otherwise).

Non Drop-Frame Timecode works simply and elegantly in EVERY situation, provided the "NDF" option is selected in the menus. There are no other complications if keeping everything in the Non Drop-Frame domain, both internally and externally. The relatively trouble-free nature of Non Drop-Frame Timecode makes it especially attractive. Non Drop-Frame mode is normally recommended for all production (shooting), and post-production (editing) processes. The only disadvantage of Non Drop-Frame Timecode, is that its numbers will not be exactly equivalent to "real" time, or "clock" time, when a NTSC-offset frame rate, like 29.97, is used. It is normally a "broadcast thing".

There needs to be a perfect phase relationship between Trilevel sync and Timecode for smooth operation. This is normally achieved by generating both signals (Trilevel and Timecode) from the same physical crystal (crystal oscillator). The Varicam jams to an external Timecode source within a few seconds of it being connected to the external source. After that, the internal Timecode generator takes over and continues to generate the Timecode until it is re-jammed again (by subsequently disconnecting and reconnecting the external Timecode source, or the camera is powered OFF and then back ON again.). Since the Timecode is really generated internally, I'm wondering if it is best to have the camera generate its own video sync internally as well, in order to preserve the critical phase relationship between them. So for an application where you are trying to get the same Timecode on all cameras, it seems best to connect the Timecode coming from the "Lockit box" only (and leave the genlock disconnected).

When shooting High Definition in a NTSC environment, the camcorder's System Frequency is nearly always set to 59.94Hz for practical reasons, and therefore delivers 29.97 Timecode. Most Varicams are set to 59.94Hz to make them backwards compatible with analog television (NTSC) systems and related equipment. This effectively makes the Varicam a "29.97 camera" in terms of Timecode for nearly all applications.

The following schematic shows the correct dip-switch settings when using the Ambient ACL202CT "Lockit" box (= external Timecode and Trilevel sync generator) with the Varicam HD camcorder set to a System Frequency of 59.94Hz. If you try to send a Varicam anything other than 29.97 Timecode (and SMPTE 296M Trilevel sync) from an Ambient ACL 202CT "Lockit" box, the system will "freak out" and produce glitches in the image.

This next schematic shows the correct dip-switch settings when using the Ambient ACL202CT "Lockit" box (= external Timecode and Trilevel sync generator) with the Varicam HD camcorder set to a System Frequency of 60.0Hz. This would be a typical configuration when shooting for European television and similar PAL-based countries.

Disclaimer: While I check the information presented here as thoroughly as possible (...through actual work experience, personal testing, and consulting other experts in the field), I can not absolutely guarantee its complete accuracy. These writings really reflect my own evolving understanding of these particular issues as I try and piece everything together myself. These pages are works in progress, and will be corrected and updated as new information comes to hand. Any and all feedback is very gratefully accepted. Especially any information that helps to correct outright mistakes in this presentation, or additional information that helps to expand the scope of these discussions.

Peter Gray
(in California)
P.O. Box 5132
Pine Mountain Club, CA 93222
United States of America
cell: +1 (661) 219-3981
telephone1: +1 (661) 268-1530
telephone2: +1 (661) 242-1234

dit@petergray.org