Understanding SMPTE

[Stephen]

Hi all,

I thought I could work it out, but I'm struggling a lot and would appreciate some help. I've read a lot about SMPTE but I just can't put the pieces together and see exactly how it helps me. (and how to use it)

(Sorry if this gets too long)

Scene 1. - In my room.

I start a microphone recording from my computer.
I start my dvx recording.
Clap my hands real loud so the mic hears it and my cam sees it.
Record 10 minutes.
Stop both.
Link up the beginnings of the video and the audio so the clap is in sync, and that's it.

Does time coding come in to this scenario in any way?


Scene 2.

Same as above, except, some time during the recording I stop the cam for a few seconds or something and then start it again.
Now it starts getting confusing.

If I keep recording non-stop then they will link up nicely. But if I stop recording my video to move around, then start again, then my audio and video is messed up from that point on. What do I do in this case?


Logic. (This is maybe why I can't grasp it)

What makes sense to me is something like this...
Synchronise the audio and video by linking the devices. The sync should be to time, not frames. (Like in the movies when the bank robbers all set their watches to the same time)
Start recording both devices.
If I stop either device, the timer should carry on, (not stop like smpte), then if I start it again, it will continue recording and still match up to the correct time.
Then in the editing software, all the audio will match up to all the video according to the exact moment in time that it was recorded.
Then if 10 cameras and 10 microphones were recording everything, they're all synced nicely and I can choose which recording and which scene I want.

(Hope this makes sense)

Please someone help out before I go mad.

 

[mikkowilson]

SMTPE is just the format of Time Code.

Your theory of freely running time code is correct.

Consumer cameras only only advance time code when recording. This known as "rec-run" timecode.

Professional cameras, including the DVXs and HVX, also have the option to freely advance timecode. This is called "free-run" timecode.

You can choose from the menu which to use.

- Mikko

 

[Stephen]

That's a HUGE relief.

I switched on my cam quickly now to test this. It's a BEAUTIFUL sight to see that time code moving regardless of whether I'm recording or not.

Thanks for your help.

 

[Stephen]

I'm curious, (and a bit frustrated)

Is the Firewire on the DVX100 the only output that outputs an SMPTE time code?

Does the video or audio also?

I seem to recall reading somewhere that the focus iris or zoom s/s minijacks can be made to output this also. (It might have been a little converter box that plugs into one of those jacks that does that).


Reason for asking...

All over the place, I see word clocks and smpte ins and outs, but they are never firewire. (Unless you pay the earth for it - where the frustration comes in)

I have a card in my PC with a time code generator on. It has a Word Clock in and out, SMPTE in and out, and an MTC out - not forgetting plain old MIDI.

Is there a way I can link my cam to my pc so I can sync them?