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Author
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Topic: No more Pedro Box for Stereo sound sync
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Winbert Hutahaean
Film God
Posts: 5468
From: Nouméa, New Caledonia
Registered: Jun 2003
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posted August 16, 2009 11:23 PM
I don't have a Pedro Box but from the previous thread here, I got some idea how Pedro box works. By using Pedro therefore:
1. We need a separate box for PAL and NTSC films
2. We have to precisely start the DVD at the exact frame with the 8mm
3. We are not recommended to do reel changeover very often
4. We require to use a fit GS 2100 machine
5. Only GS 1200 can work with Pedro
6. It is best to do for re-recording/re-dub the soundtrack (not for a live sync)
Now, I have also collected some issues that become constraints in using Pedro:
A. Not everybody owns the most high end machine, GS1200
B. (some people) When receive originally in multiple reels, don't want to put in bigger reel because of many reasons
C. When we have the films in different languages, we feel guilty (sorry) to re-dub it with soundtrack coming from dvd (say, the film is originally in English then to be re-dub to Italian. Meaning the English version will be totally removed)
D. Cannot be used for Digest/Edited version
However, after finding another invention in sound reproduction (which is totally not related with 8mm), I got some idea that with this invention we can still produce stereo sound for our 8mm films without a Pedro box.
It starts when I wrote this thread and especially focus on a new turntable with time code vinyl.
You can click this to see time code-vinyl.
Briefly and basically, there is no music on time code vinyl but only a sound of pulse code which is sent to computer (it does sound like fax tone). Then computer will read that code to be correspondent with the data (sound format/MP3). So wherever the DJ is slowing down or forwarding/backwarding the vinyl, it will quickly change the sound in the computer to follow it.
Now what we need is at least a projector with stereo sound capability and the film with a balance stripe.
Step No 1, we record the time code sound (from the time code vinyl) to the balance strip. We don't need to give a cue when recording the time code sound, just start record at any place on the balance stripe. The computer will create the cue later on.
Step No. 2, we reformat the DVD source (which has the same cut/edit) to MP3 format and then link with scratch live box.
Step No. 3, the sound from track 2 of the projector is linked with this scratch live box and we give a cue where the first frame at the projector should be correspondent with the MP3. This cue will be saved in the computer for next show.
With this method therefore:
- Basically we can use any projector (a mono projector will require a totally remove of the original soundtrack of the 8mm film, while with a stereo projector, it can be placed at balance stripe).
- If projector is slowing down (because of a weak motor or belt problems, for example) then the MP3 sound will also slow down.
- No more NTSC vs PAL problem, because we are synchronizing with a sound format not a picture system.
- We don't need to splice all multi-reels into bigger reels. Reel changeover is not a problem because the time code will give a different code for each reel. While on the other hand,1200 feet reel is also not cheap.
- It is done for a live synch, so if we are using 2 track projector/stereo projector we can still keep the original soundtrack on track 1 of the 8mm film.
- Can be done for a real 5.1 DTS sound
I have also another idea of using this method for a digest/edited version. But I will explain later on.
Now, I need your input, will that method works? What do you think? Your comment please....
regards
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Winbert
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Winbert Hutahaean
Film God
Posts: 5468
From: Nouméa, New Caledonia
Registered: Jun 2003
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posted August 17, 2009 08:40 PM
quote:
I'm not sure that the 8mm sound stripe will reproduce the Timecode Signal in an accurate way. Dropouts could lead to glitches in the timecode-readout which will cause the sound to "jump", too. Did you run a test yet?
Joerg, honestly, I haven't run any test. The Scratch Live Box + Serato software is about $600 and I don't have that muchmoney.
But from many readings, I got infos that to read the time-code vinyl can use any needle, even a worst one. So if we transfer the time code to balance stripe, as long as it can produce a good sound, I think it will work
quote:
In my opinion, the main problem is that both the projector and the timecode source record have to run crystal-locked when recording the timecode signal onto the sound stripe. Otherwise, you won't get a real time reference on your print and the soundtrack won't stay in sync at all.
If you see that test done by DJ on youtube, there is no need to run crystal-locked because the needle can be placed at anywhere and the software will find (in mili second) where the right place to start. I can imagine that the time code (in laymen wordings) like a bunch of numbers from 1 to millions. So the beginning of track is no "1", followed by "2", "3", etc. And the Software also place those numbers on MP3 . So wherever we place (say in code no. 38730) the software will run to find that number on MP3.
So, when we moved those numbers (time code) to balance stripe then we need only to cue the first number (i.e the first frame) and the other numbers will follow.
I think it is roughly similar to the old way when recording films was using perforated reel to reel tape.
quote:
infact Wolfgang Peter Thuille (the creator of the 'Pedro' sync box) produced different variations of his boxes and so the GS 1200 is not the only projector that can work with a sync box.
For example the BAUER T502/T510/T525/T610, with an adaptor, can work with a sync box too...
Flavio, you may be right, but those are still high-end machine. However with Serato and Live Scratch Box, we can use any simple machine as long as it is a sound projector.
About the NTSC vs PAL, you are right, there is now a dual system box. But the box is only used to crystal lock the machine. Here, I am thinking to apply a similar DTS reproduction system in a real cinema (and in fact we can use a real 5.1 DTS as the source)
I need some more inputs, especially from those with computer expertise.
regards,
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Winbert
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Joerg Niggemann
Expert Film Handler
Posts: 127
From: Germany
Registered: May 2006
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posted August 20, 2009 03:28 AM
Winbert, let me try to explain in another way. With scratch live box, you have 2 audio tracks which have to run in sync: A Vinyl record as master and the audio track as slave. No Problem: the box reads the time signal and takes care that the audio track is played back according to movement and time position information of the vinyl record.
If we come to our 8mm film, we still have 2 Audiotracks to sync and they may run together according to speed changes of the projector, BUT there is NO relation between time signal,film and soundtrack until
- you lock film to 25 or 23,97fps during the record process, depending on the source of your soundtrack.
- you take care that the vinyl record is running locked to exact speed where it counts as a real timebase.
Think about the "cheap" Projector: let's assume it is running at 24 fps exactly and the vinyl record counts one second in one second. Now you record the signal to the stripe. The recorded signal will count one second every 24 frames of the film. During Playback, box and software will advance the soundtrack by one second every 24 frames of the film. If the projector slows down, the soundtrack will slow down, too. Fine. BUT: If you have taken the soundtrack from a PAL DVD, one second soundtrack advance corresponds to 25 frames advance of the original DVD movie. As a result, the soundtrack will always run too fast at 25fps, compared to the projector running at 24fps.
Now record the time signal to the projector running at *crystal locked* 25fps: The signal counts 1 second every 25 frames. Playback with "cheap" projector: Box tells soundtrack to advance 1 second every 25 frames of 8mm film, regardless of film speed being 24, 25, or whatever fps. Soundtrack will stay in sync.
Joerg
[ August 20, 2009, 08:03 AM: Message edited by: Joerg Niggemann ]
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Joerg Niggemann
Expert Film Handler
Posts: 127
From: Germany
Registered: May 2006
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posted August 21, 2009 11:01 AM
Please don't take me wrong Winbert, but let me try one last comment ;-)
Yes, the box will slow down mp3 when Projector slows down. But only related to the speed the projector was running at when recording of time signal was done.
If time signal recording was done at projector speed 24 fps and you play it back again at exactly that speed, the box won't change speed of mp3 playback. I think you can agree with that. Now, since your mp3 soundtrack came from a DVD movie of 25 fps, in fact sound is running too fast in that case, if it is not changed.
If Projector slows down to 23 fps or speeds up to 25fps, Box will slow down/speed up mp3 to "speed" of 24/26 fps. Still too fast and always one frame too fast because film reference speed was fixed at 24 during recording of time signal.
What you do with that is sync mp3 to time signal. But you also have to sync film to time signal once before film with time signal can sync mp3. If you don't do that, sync is only relative because overall speed is wrong.
Last thought about relative sync: What do you think happens if projector runs at only 18 fps when you record time signal? Playback at 24 fps would end up in soundtrack running at "30fps", because time signal and film have been synced to 18 fps reference film speed.
Maybe another member can help to put it in the right words. Very difficult to do in a foreign language, and I think my comments have to end here...
Joerg
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Joerg Niggemann
Expert Film Handler
Posts: 127
From: Germany
Registered: May 2006
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posted August 22, 2009 03:36 AM
Patrick, you are right. The audio file has nothing in it referring to fps. But what do you know about playback speed of that file? You know that it refers to the DVD where it came from, and the movie on that DVD has exactly 25fps for PAL. You need to know that because if you play back the audio file unchanged, your 8mm print has to run at 25fps, too. That's why I talk about "fps" also related to the audio file. 25 fps "speed" of audio file and film print is the overall reference speed you have to consider here. As long as reference film speed is missing because time signal has not been locked to film speed, the setup won't work.
Winbert, please think about the following setup:
You record the time signal to the soundstripe. Projector is running at 24 fps. Now play back the recorded time signal, same projector speed. Will the mp3 speed be changed or does it run at "normal" speed in this case?
--> mp3 speed will be unchanged, because projector and time signal had the same speed during record and playback
Again you record time signal to soundstripe. You use the same print and the same mp3 track. Now your "cheap" projector is running at 25 fps. Playback the film with recorded signal again at 25 fps. Will the mp3 speed be changed?
--> again, mp3 speed will be unchanged, because of same speed during record and playback.
Now if you compare these two cases, you have the same print, the same mp3 at the same unchanged speed, but your projector is running at 24 fps in case1 and 25 fps in case2. Can the sound be in sync at all?
Joerg
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