8mm Forum: sound-sync and MIDI

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Posted by Steven J Kirk (Member # 1135) on December 03, 2008, 08:42 PM:

Okay, here's a hypothetical. Pondering on syncing up stereo sound from a high quality source to a super 8 print it has struck me that the balance track on my twin track machine ( or on a stereo machine ) could take a sync pulse. Then you drive the tape machine that could be 5.1 or anything from the projector sync. I was thinking of a Portastudio which can be found secondhand quite reasonably. Okay, so I see a Korg digital 8-track machine with MIDI IN and OUT. My question is can MIDI be recorded on a super 8 balance track? If so, you could have any soundtrack - this Korg would take 6 tracks - and play back in sync with a super 8 film print. Am I making any sense?

Posted by Bart Smith (Member # 780) on December 04, 2008, 02:03 AM:

You can't record MIDI directly on a tape (whether it be a standard audio tape or the balance track on a Super 8 print), as it is not in any way, shape, or form an audio signal. This is a very common misconception, and is doubly confusing to those unfamiliar with MIDI as the standard MIDI port uses the same 5-pin DIN socket that was also commonly used on some older audio equipment, and as MIDI ports are most commonly found on musical/audio equipment.

MIDI is a stream of data essentially, relaying various command events between bits of equipment which use it. For instance a MIDI keyboard 'tells' a sound module/synthesizer etc. that note 'x' has been struck at velocity 'y'. When the key is released is transmits a different command to let the synthesizer know that note 'x' had been released. The synthesizer generates audio based on its interpretation of those data signals.

Getting back on track, another stream of data in the MIDI standard is MIDI timecode (MTC). It is this signal that the Korg etc. will use to synchronize itself to external devices ('slave'), or it can generate the MTC in which case other MIDI devices can synchronize to it (in which case it is the 'master').

To use MTC sync in conjunction with an audio recorder you need to get another box of tricks, a MIDI to tape sync. These come in various flavours, but the most sophisticated and suitable type for these purposes would be a MIDI to SMPTE unit.

In theory the following might be possible:

1) Your high quality soundtrack is recorded on the digital multitrack.
2) You play it back (it is the master generating MTC) and connect the MIDI out to the MIDI in of the sync unit. The sync unit generates its audio signal (derived from the MTC that the digital multitrack is generating) which you record onto the balance track using the projector.
3) Set the digital multitack to slave, rewind your film and set the projector running. The audio output is connected to the audio input of the sync unit. The sync unit converts this back into MTC, and the multitrack should start running in time. This would only work if the balance track is capable of holding the bandwidth of information in the SMPTE soundtrack which it may (or may not) be able to do.

HOWEVER...

It isn't that simple! The above example would work fine if your soundtrack was something you had composed yourself stored as pure MIDI data without the use of long samples or audio recordings. If you have simply recorded a 5:1 soundtrack off a DVD or whatever onto the multitrack in MIDI terms it would be a single event. A signal would tell it to start playing, and it would wait for another signal to tell it to stop. You would lose sync. I could go into this in greater detail but that would take too long!

So the only relatively easy approach would be to use a projector with external crystal sync such as the GS1200. In which case you would be pretty much as well off just playing back the DVD in the first place, the only real advantage that I could see with using a digital multitrack is that you could probably be able to get the soundtrack to start at exactly the correct point, and you would be able to edit the soundtrack to remove portions of it that aren't on the Super 8 film. You could isolate the portions of a soundtrack from a DVD that are found in an edited digest and stitch them together in sequence for example (but then again you could do this last bit with a computer anyway).

So yes you could do something along those lines, but it would be quite a bit of effort. The other problem is that most digital multitracks have finite internal storage, so you would only be able to fit a few movies onto it (unless you had load of hard drives that you kept swapping out).

I'm sure I've missed out some other pertinent points, I guess what I'm trying to say is that it isn't as simple as it may first seem, and certainly not at all easy with 'prosumer' recording gear like the Korg you mention.

Posted by Jim Carlile (Member # 812) on December 04, 2008, 02:53 AM:

In other words, render to Caesar the things that
are Caesar's. Don't mix apples and oranges. And don't mix the grape and the grain, etc.

Posted by Steven J Kirk (Member # 1135) on December 04, 2008, 09:18 AM:

Thanks very much for taking the time to make that full explanation! I thought it wouldn't be that straightforward because I had searched this site and found no mention of MIDI. I also knew someone would know the answer. I don't have a GS1200 but entertain the idea of running better quality soundtracks in sync with Super 8 and 16mm. I'd prefer a way to do it without changing the original Super 8 sound. I have a 16mm print of APOCALYPSE NOW and of course the DVD with great sound. Running the two togther remains an ambition.

Posted by Keith Ashfield (Member # 741) on December 04, 2008, 09:42 AM:

"LOOK OUT! - Jim's mentioned that word "GRAIN".

Can't you just feel Christopher P "cringing" again? (or should that be a-grain?)

Posted by Winbert Hutahaean (Member # 58) on December 04, 2008, 08:42 PM:

Hi Steven,

If your idea come to a real, I would imagine that we can play the sound from DVD source. And it does mean, we can switch the soundtrack to English, French, Africans, whatever the language available in that disc.

Amazing.... I wish...

cheersm

Posted by James N. Savage 3 (Member # 83) on December 09, 2008, 09:51 AM:

Sorry guys, I'm a little slow on these things.

By MIDI, I think you mean "mini-disk" (right [Roll Eyes]

?).

I would have thought that the digital sound could easily be transfered to standard magnetic tape, since we can record DVD to our film's magnetic tracks.

Am I missing something?

James.

Posted by Michael O'Regan (Member # 938) on December 09, 2008, 10:14 AM:

MIDI = Musical Instrument Digital Interface.

Posted by James N. Savage 3 (Member # 83) on December 09, 2008, 11:47 AM:

Oh, boy.... [Embarrassed]

Do I feel like an idiot!

James.

Posted by Michael O'Regan (Member # 938) on December 09, 2008, 02:17 PM:

Its not a term that comes up too often related to film collecting.

Posted by Christopher Quinn (Member # 831) on December 10, 2008, 11:54 AM:

Steven, has the colour held up on your Apocalypse Now print?

Posted by Steven J Kirk (Member # 1135) on December 15, 2008, 07:47 AM:

Yes, the colour is pretty good. I'm no whiz when it comes to working out the film stock. It's a widescreen / masked print, however.

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