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Author Topic: ID Frames and their effect on Sound Darren Briggs Master Film Handler Posts: 371 From: York, UK Registered: Dec 2001 posted 02-02-2003 05:06 PM                        Analogue sound is 20 frames ahead of the picture. Just count the frames on your head leader, from any number laced in the gate to the diamond printed on the film which lines up with the optical sound head. This should always be checked when lacing a film (im sure you should already know this) if not you may be lacing the film up with out of sync sound. This is a basic rule of using a film projector. If you laced it up 2 perforations out of sync and the film was printed with sound 2 perforations out of sync, your sound could be a whole frame out. You should check the Picture and Sound sync marks on the head leaders of the film. And is the film was printed out of sync, you could then lace up to compensate for this. Digital basement readers would also be out of sync if laced incorrectly. Penthouse readers depend on the correct top loop. Darren  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 02-02-2003 05:34 PM                    There is a difference between the official standard and the normal practice as far as analog sound pullup is concerned. As for the ID frames in question the only way we'll ever know for sure would be to try it both ways or digitally edit a copy of the non cut version. Even if Brad's assertion turns out to be true for this join it still represents poor editing that is ignorant of 75+ years of sound on film experience as regards where to put the breaks when balancing reels and it remains an open question as to how much the projectionist needs to try to accomodate sloppy editing. For example, while this situation won't affect me as a reel to reel operator there are others that do, namely dialog too close to the beginning or end of a reel resulting in part of a syllable being lost on changeover. But I have no intention to start using a platter just accomodate crappy editing. (Although I did build part of Russian Ark the last time I ran it but that was a special situation. Yes, I left ID frames even there.)  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 02-02-2003 07:45 PM                     Alright Steve, since you just don't believe me, here is a quick sloppy example of why platter people should not be chopping ID frames without looking at the track first to make sure they will not be permanently cutting out audio continuity. I hope this is simple enough for everyone doubting to understand. If not, I'll start collecting reel change examples over the next couple of months and make a huge page in the tips section showing real life examples. Still I definitely agree with you that this entire argument of whether to cut or not is all because of sloppy reel change placement. However that is out of our hands and anyone running a platter, tower, or building to large reels should respect the film enough to make sure that they are not causing damage by chopping off 2 frames when they build it up (1 per leader). If this wasn't such a somewhat common problem, I wouldn't have a problem leaving an ID frame in tact on the leaders. Click here (I couldn't post these pictures on this particular thread due to the size of them.)  |  IP: Logged Joe Redifer You need a beating today Posts: 12859 From: Denver, Colorado Registered: May 99 posted 02-02-2003 08:13 PM                        Well this isn't even an issue at all if you don't normally cut ID frames from a new print. But yes, two frames is a lot and having edited 5.1 and 2 channel audio myself I can tell you that looking at the waveform DOES represent whether sound will be smooth or jumpy. Sure, you have to look a bit closer at 35mm analog audio since it is so small, but other than the size the way it works is exactly the same.  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 02-02-2003 09:18 PM                    Hehehe...nice demo but let's see what we have there. You've taken a piece of audio/video where it is known in advance that all the major modulation is narration, snipped out two frames at the start of some modulation and predictably ended up cropping a spoken word. That's pretty much preordained given the material and doesn't really address anything except that cropping words is bad, not whether some random place where modulation increases is necessarily equally bad. Like I've been saying all along, I don't claim you're wrong only that you don't know. To make your point you'd really have to look at random points in a random, unknown track and make snips at the start of a major rise in modulation and then listen to and see how often the snip causes a noticable disruption. And even that may not represent a totally fair test since one presumes that for the most part editors still do tend to respect the reel change areas. A big modulation change may mean they didn't but then again it might not. Oh, and despite the nature of the demo it wasn't all that much of disruption. The small pop occurring at the typical unblooped splice is worse.  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 02-02-2003 09:26 PM                     Steve, ANY snip of a rise in modulation like that is noticeable. Go ask any professional audio editor. I picked that piece of dialogue since it was something I had convenient and because I knew it would be a demo that anyone could hear on crappy computer speakers. It does not have to be dialogue though. I'm sorry you cannot comprehend how audio works, but this is the way it is. Do you really think audio editors look at the waveforms of the audio because it looks cool? No! Do manufacturers of software put waveforms on their programs because it makes it look more high tech? No again! The whole point is for the editors to be able to visually read the waves so they can better do their job. This is no different. It is one thing to say that you do not personally find such an interruption distracting, but that is your opinion and you are trying to pass it off as fact. Jumps like that are very distracting to me, again...my opinion. However the fact remains that if you lose 2 frames worth of audio at a point where it is rapidly getting louder or softer (over a 2 frame period), it WILL be noticeable. Again, fact.  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 02-02-2003 09:28 PM                    I'm sorry you feel the need to slight my knowledge and experience. My background is in post production.  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 02-02-2003 09:29 PM                     In this specific area of post production audio editing, I'm afraid it is lacking a bit. Your post is every bit as insulting to me as my post appears to be to you. I have spent much time in post production as well. I guess it all depends on how picky someone is. Blips like that are unacceptable to me. Heck, hairline scratches on the picture are acceptable to a lot of people, but I'll bet neither one of us would be too happy about it. You asked and I gave you a quick example. I think we are done discussing this with each other. Fortunately you run a changeover theater and do not cut frames, so this really doesn't even apply.  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 02-02-2003 09:37 PM                    Insulted? Are you really insulted when someone respectfully disagrees with you?  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 02-02-2003 09:41 PM                     Pick whatever word you want Steve. Am I really angry about it? No. I used that word because that is how I interpreted you as interpreting my post before. If you want to nitpick words newsgroup style, email me as this is a waste of space here since we've both already stated our arguments.  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 02-03-2003 09:04 AM                        Darren Briggs wrote: "Analogue sound is 20 frames ahead of the picture.Just count the frames on your head leader, from any number laced in the gate to the diamond printed on the film which lines up with the optical sound head." NO! The analog sound is printed 21 frames ahead of the corresponding picture frame, per standard SMPTE 40. The 20 frame offset shown on the threadup leader gives a 1/24 second advance to the sound, assuming it takes that long for the sound to travel from the screen speakers to the center of the audience.  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 02-03-2003 10:54 AM                        .....and that spec was written way back in the day when even neighborhood single screen theatres were huge compared to most of today's multiplexs. Nowadays, if you are threading for anything from a screening room to a modern, moderatly sized cinema, lipsync would be accurate with zero advance. Frank  |  IP: Logged Mark J. Marshall Film God Posts: 3188 From: New Castle, DE, USA Registered: Aug 2002 posted 02-03-2003 11:51 AM                    When you do changeovers, how is this compensated for, do processors fake a slight fade between the two sources, or does the sound jump right from one reel to the next? It seems to me that even while doing effective changeovers is easy to do, getting them to be as EXACT as splicing reels together would be extrordinarilly difficult given power fluctuations, motor position, ramp up speed etc.  |  IP: Logged Dustin Mitchell Phenomenal Film Handler Posts: 1865 From: Mondovi, WI, USA Registered: Mar 2000 posted 02-03-2003 11:54 AM                     Not wanting to get in the middle of the Steve Kraus vs. Brad Miller ID Frame Deathmatch I'll just repeat the advice I give every time this thread comes up. If you do leave ID frames, only leave one on the head of every real. There is no reason to have an ID frame on each side of the splice or each end of the reel to identify it, one is sufficient.  |  IP: Logged Leo Enticknap Film God Posts: 7474 From: Loma Linda, CA Registered: Jul 2000 posted 02-04-2003 02:27 AM                        Jeffry L. Johnson writes: quote: DTS is offset zero frames. SDDS P side is offset zero frames. SDDS S side is 17 frames behind picture. Then presumably that means that DTS and SDDS reproducers have to be positioned a minimum distance in front of the gate (i.e. the film passes the reproducer a minimum of X frames before the gate), and that without redesigning the encoding protocols used, a combined basement reader such as are available for Dolby digital and analogue will never be possible. I wonder what the logic behind that decision was, given that it inherently limits the flexibility you have in installing the hardware?  |  IP: Logged

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