Stereoscopic Multiplexer Tape Synchronization

The tape synchronization feature has been developed to watch 3D recording, using the DV camcorders as playback devices. It is no longer necessary to transfer the recording to hard disk in order to watch them. Tape synchronization is well suited to get a first preview of your recording. It is not indented to be used for public presentations, however, because it doesn't guarantee that playback will be 100% in sync. Tape synchronization doesn't release you from editing your stereo recordings. But it is an invaluable tool to get an immediate stereoscopic preview of your tapes. Such an immediate preview will help beginners to recognize mistakes, long before editing is done. Professionals appreciate tape synchronization as well, because playing the dailies in 3D becomes a breeze.

How to use tape synchronization?

This guide assumes that the camcorder have been connected to the computer and  Stereoscopic Multiplexer has already been configured (if not, see here how to configure it). We recommend to use Stereoscopic Player as playback application. In Stereoscopic Player, click File>Live Video>Stereoscopic Multiplexer to load the Stereoscopic Multiplexer. If your camcorders start playing, press the Stop button or click Playback>Stop. Next, click File>Format Properties and make sure that the following options are selected:

  • Ignore timestamps
  • Synchronize DV tapes
  • Play audio
  • Deinterlace

Ignore timestamps should always be selected when using DV devices. Timestamp-based synchronization doesn't work well with DV devices and might cause a mis-sync of one frame. Tape synchronization enables the tape synchronization feature and Play audio will pass the left camera's audio data to the sound card. If there is a direct audio connection between the camcorder and your A/V receiver, you can leave Play audio unchecked. Deinterlace removes weave artifacts from the video.

Click OK to close the configuration dialog.

Switch you cameras from camera mode to play/edit mode. Click the Pause button in Stereoscopic Player. Both camcorders should switch to pause mode. Make sure that left and right tape are showing the same scene. If not, use the buttons on your camcorders to rewind them to the same scene. It's not necessary that they are positioned on corresponding frames, only the same scene.

Press the Play button in Stereoscopic Player. The first scene will be out of sync. When the first scene change occurs, Stereoscopic Multiplexer synchronizes the tape drives.

How does tape synchronization work?

Stereoscopic Multiplexer parses the DV stream to detect scene changes. Whenever a scene change occurs on one tape, but is missing on the other tape, the tapes must be out of sync. Consequently, it pauses the first tape until a scene change occurs on the second tape as well. Once both tapes have passed the scene change, the multiplexer steps back to the first frame of the scene. Finally, it sends the play command to both tape drives. The process starts again when the next scene change occurs. If there is no need for resynchronization, the multiplexer will continue playing without interruption.

How does the Stereoscopic Multiplexer control the camcorders?

Via Firewire connection. Firewire is used to transmit video, audio and control data. Other kinds of connections are not supported for tape syanchronization.

How does the Stereoscopic Multiplexer detect scene changes?

DV tapes store the recording date and time of each frame. If the recording time of two consecutive frames differs by  more than a second, there must be a scene change. No image analysis is done, so tape synchronization will not affect playback performance.

Tape synchronization will not work if you did not set the date and time on your camcorders (if the time is 0:00:00 on all frames).

What is required for tape synchronization to work?

You need two camcorders with DV out connector (DV video tape recorders are suitable as well) and a computer with two Firewire controllers (these requirements are not specific to tape synchronization but are general requirements). Important: You need two separate Firewire controllers, two connectors on the same controller are not sufficient!

During recording, date and time must be set on both camcorders. For each scene, recording must be start at the same time, e.g. using a LANC or IR remote control. Only LANC remote controls, for example the ste-fra LANC, are able to keep mis-sync below 1 ms (which is highly recommended). Pressing the recording buttons manually is not recommended, since you will not be able to press them at exactly the same time. If the camcorders did not start recording at the same time, playback will be out of sync as well.

There should be the same scenes on both tapes. If a scene is missing on one tape, do the following: Press the Pause button in Stereoscopic Player, fast forward the tape with the additional scene (using the buttons on your camcorder) until both camcorders are located on the same scene again. Finally press the Play button in Stereoscopic Player. The multiplexer will resynchronize at the next scene change.

How well does tape synchronization work?

The mis-sync is usually within ±1 frame. The Stereoscopic Multiplexer does not perform resyncing if the mis-sync is equal or lower than one frame. We believe it makes sense to tolerate a one frame mis-sync so that resynchronization occurs less often (which pauses playback for a few seconds). But we might add to force resynchronization  for one frame mis-sync in future versions, depending on customer feedback.

When to use tape resynchronization?

Tape synchronization is meant to be used for previews only. Don't use it for presentations since there might remain a mis-sync of one frame and playback will be interrupted for a few seconds whenever resynchronization takes place.

Which camcorders can be used?

It should work with all DV devices. Obviously, we were not able to test it with all camcorders available. If it does not work with your camcorders, please tell us.

Is it dangerous for my camcorders or tapes?

No. Nevertheless, we advise against using you most valuable tapes for the first try.

The resynchronization process causes additional stress for the tape drives as well as the tapes so that they might wear off more quickly. To avoid early failures, don't use tape synchronization in continuous duty.

Pressing the Play, Pause or Stop button in Stereoscopic Player chancels the resynchronization process at any time.