How to make sure a continous timecode ?

[Peter Rixner]

Hi :)

I really haven't found a reliable way to get a timecode without missing frames. I am aware of the problem with mpeg not having all the frames. But I am not the manufacturer :)

So I always record a few seconds colobars when a shot is done. Then when I want to continue I make sure to be in a running timecode. Then Stop. Chance to cameramode and continue recording. But still many times the result is a short stop in the timecode. The same thing when in VCR mode, wanting to record edited Maeterial from Premiere via Firewire.

It seems to work fine with the end-search function. But thats useless, if you wand to recor from a prerecorded spot or when removing tapes and so on.

So is there a secret (or obvious) method to force the z1 to record from the nearest, complete frame to my stop point. Something like: OK, I want to record from 00:20:00:00. Finde me the nearest full frame. This then could be 00:19:59:14.

OK. I guess I made my problem clear to see :)

Thanks!

Peter

[Dominic Jones]

You need to black and stripe your tapes before use.

This means recording over the full tape with black silent frames, thereby generating a continuous timecode to record over.

You can do it though the camera (with firewire link to your NLE with no project selected - this should send silent black frames), but you'd be way better off doing it with a deck to save your camera's heads. I don't know whether you can, but if you can stripe a tape on a DV camera/deck and then shoot in HDV on it - that would be useful...

Anyone tried it/know?

[R Geoff Baker]

You can't stripe a DV tape -- the stripe is always erased by the new shoot. The only thing you can do is cue the camcorder to a the last frame of the previous shot before starting ... which is what happens with a previously used tape -- the camcorder sees the 'previous' shot and continues from there. But it isn't a stripe ...

I expect HDV is the same -- it would be an odd feature to add to any digital format to insert edit during shooting onto a previously used tape. Even legacy analog formats like BetaSP only required that for an edit master -- you couldn't insert to a stripe during a shoot!

As for HDV not having all frames, this isn't really true. All the frames are there, just not all of them have complete image data. I'd be surprized to learn that they don't have all the non-image data though ...

GB

[Peter Rixner]

Thanks for your ideas,

Still i am not sure, whats going on with the HDV timecode.

I figured out, that stopping the tape in VCR and the changing to camera mode shifts the timecode a few frames. Recording from there in cameramode makes a seamless timecode most of the times. But still not always.

But it never works when I record in VCR mode from Premiere.

Another strange thing is, that when capturing in Premiere those stopping timecode seems not to be a problem. I don't get a error message and it records just over the spot.

I don't like not beeing sure about that all ...

any ideas ?

Peter

[Andrew J Hall]

I'd be interested in understanding more about this also. I have read that not 'striping' the tape can cause problems if you want to recreate a series of source clips from the original reels (in situations for example where you have edited in DV and now want to use the same edits to create a HD version).

Andrew

[Dominic Jones]

Geoff, sorry mate, but that's not the case.

You certainly CAN stripe a DV tape, and the camera will record over the frames but not the timecode. Done it a million times. Timecode is generated on DV only the first time it is recorded. After that the camera uses the current timecode on the tape, so unless there's a break i the TC you will have continous TC even if you fast forward the tape in between shots.

What you CAN'T do on DV is set an externally generated timecode or start from any point other than 0:00:00:00 (well, actually, you can - but not on the majority of equipment, and certainly not on lower end cameras)...

Not sure what the deal is with HDV as I have yet to buy a camera - but that is *definitely* the case for DV.

[R Geoff Baker]

You are absolutely wrong. The camcorder will always, without fail, without exception, record a new timecode track. No model built or sold offers insert on a stripe while shooting ... the only models that ever offered insert were decks, and only during editing.

This can be proved quite easily, with a little experimenation. It can also be confirmed with Google searches, or discussion with equipment experts.

The only thing striping does is ensure that you are shooting on used tape, and that there is a timecode value for the camcorders heads to read & start the new recording based on that value ... but once it starts it behaves as it always does and records a new timecode track. This can cause big problems with tapes that have stretched, or been frequently ejected, as the old values will drift out of sync with the new values and cause a discontinuity with the next start.

But that's beside the point -- my claim is quite true -- no stripe preservation in camcorder.

GB

[Christopher C. Murphy]

Correct me if I'm wrong, but DV tape isn't like analog tape.

In the analog world there is "burn" via "control track", but in the DV world the TC is put down in real time when recording. Whether it's the 1st or 10th time recording it doesn't matter. Once you pop a fresh tape into the drive and hit record it's laying TC. If you notice when you record something and then rewind to check your work...it's timecode that it's using. But, when you fast forward again to get to the end of the footage you'll see blue video.

I believe that's why you have to start recording "in video" whenever you've jumped the control track in analog video, but you can still record on blue video in DV. It just start laying TC at that point. However, I always rewind to video because of my analog days. I remember projects getting all messed up when you broke the control track. You had to dub your tape and lose a generation so you could keep editing!

[Douglas Spotted Eagle]

Geoff and Christopher are correct.
If you stripe a tape, then record images over it, new TC is laid in. If you make a break in the new timecode, and time passes between the end of one shoot session, and the beginning of the next shoot session, you see the old time code "beneath" the new. But you're always laying new T/C in the DV world in the majority of cams out there.
the Z1 has a few other options, including offset, but....that's turning into another subject. :-)

[Christopher C. Murphy]

Douglas, I read your "Studio" article...good job. Also, are you part Native American? I've got a little Joppa in me (east coast tribe).

[David Kennett]

There's something else which may be coming into play here! In MPEG encoding each group of pictures (GOP) has a header telling the number of frames in that GOP. Normally there are about 15, but my JVC HD10 has a six frame GOP. In normal MPEG encoding a new I-frame (independant frame - a complete frame not relying on data from a previous frame) is inserted at the beginning of each scene EVEN IF THE PREVIOUS GOP IS NOT COMPLETED. The previous scene's header then reflects the shorter-than-normal GOP.

Look what happens in an in-camera edit. Either the camera must synchronize to the GOP "flow" of the tape before an edit OR it will more likely shorten tha last GOP from the previous scene by not paying attention to the GOP structure. This means that the last GOP from the previous scene will NOT have the proper header identifying it as a short GOP.

I KNOW the edits in my HD10 are not proper. The camera drops audio momentarily during playback. The included capture software only captures individual scenes. The Ulead capture program loses audio sync.

All this points to a likely discontinuity at in-camera edits, which could easily cause a disruption of time code. Hopefully the Sonys do better at this. Anybody shed any light on this? Inquiring minds want to know!

[Ben De Rydt]

Are you sure Quickrec is off [Menu / Others]?

I have an FX1 and not a Z1, but from the little information I can gather from the manual, Quickrec can cause timecode breaks.

I think that the basic idea of Quickrec is to allow you to rapidly start recording when the tape has stopped rolling because of prolonged inactivity. Normal mode will take longer because the camera will patch up the latest GOP, AFAIK.

[Douglas Spotted Eagle]

<<<<<<<<Douglas, I read your "Studio" article...good job. Also, are you part Native American? I've got a little Joppa in me (east coast tribe).>>>>>>>>

http://www.spottedeagle.com/credits.htm

Yes, I'm part indigenous, my website goes into my background.
Glad you liked the article, I'd actually forgotten about it. There's another one on audio this month, I think.
See you at NAB?

[Christopher C. Murphy]

Douglas,

I'll be getting into Vegas on the 20th - a little later than I wanted. I'll be at the Stratosphere the 20th and Sahara from the 21st to 24th. (making a little vacation out of it) If you or anyone else is hanging out somewhere and want to get together let me know..

[Marco Wagner]

Ok. This may sound stupid, but hey, why not ask. I know what 'blacking out' a tape is. What is striping?