Position of optical sound on film in Switzerland and France

[Stefan Scholz]

Standardized with the sound on film agreement in 1930, the picture to sound distance was chosen at roughly 21 frames. Dolby stated 20 frames, not counting the image in the gate afair. So that's the same at the end.
Remember, sound travels at 1000 ft per second, a 100 ft theatre has a travel time of roundabout 1/10 of a second. 1 image is 1/24 of a second. So your loop needs to be threaded to the length of the theatre's listening position, which can mean 18, 19, or 20 frames.
Don't care too much on the subject.
Installers tended to set digital sound format sync as perfect as possible, lipsyncing all 3 formats to the optical track. That worked as long as someone else threaded the machine.

[Simone Corelli]

If dolby is counting from the BEGINNING of sound to the separation from the frame projected and the previous frame, Dolby is correctly measuring the distance in my opinion. Same if you measure from center of the visual frame to the center of the 41.666 ms sound related to this frame. Said in another way: there are 19 frames in between from sound frame and visual frame, so the distance is 20.

[Steve Guttag]

It isn't ambiguous. The standard does state to the "Center" of the related frame. I am more inclined to think that Dolby made a mistake when designing their test films and even their specification. Or decided to not introduce confusion (more like it) when you have every printed leader at 20-frames to get the sound in advance to run with that and put the Dolby Digital sound 6 frames in advance of that.

If you are threading for what appears to be good lip sync in your theatre...then when adding Dolby digital, it becomes pure math to come up with the sync adjustment for that based on where the leader falls with respect to the reader of that specific projector installation (penthouse, versus basement).

35mm magnetic is 28-frames lagging picture.

ANSI/SMPTE 55 shows their own leader and what should be printed on each frame.

[Marcel Birgelen]

I think to get to the bottom of this, what's relevant here is not so much the Dolby DA20 or any other Dolby decoder documentation, but rather the specifications that's being used by the labs that print the AC3 track, as for which exact offset they're using.

In the end, it doesn't really matter if the offset is exactly 26 frames, regardless if it's the beginning or center of frame or even if it's one frame more or less, as long as it's consistent between prints. In the end, every theater playing 35mm Dolby Digital, has been individually calibrated for lip-sync using test films and the delay should've been adjusted according to those measurements.

[Simone Corelli]

Yes, it is important to know what labs do usually.
Dolby has replied me and after a clarification I'll put the reply here for you.
I'm asking them to precisely indicate the DOLBY ideal position and the SMPTE ideal position choosing from these possibilities (without ambiguitiy!!):
pellicola_e_suono_in_italiano.png

[Marcel Birgelen]

It reads like a quiz. I miss the all of the above option.

According to the SMTPE, the reference should be at -21 from the center of the film frame, in this case, the "visual POP". Then the SMTPE allows for an additional displacement of +1/2 or -1/2 frame from there.

In that case, the sound begins position of A and C are both correct (and I expect, anything in between is considered to be acceptable), but the reference distance is wrong.

Keep in mind that up to this day, synchronizing film to sound is still often a manual job. Only since we have digital setups that can use time-code synchronization, do we have perfectly lip-sync sound recordings.

[Simone Corelli]

It reads like a quiz. I miss the all of the above option.

Thanks Marcel. Sorry but using google translator I don't understand "I miss the all of the above option"

According to the SMTPE, the reference should be at -21 from the center of the film frame, in this case, the "visual POP". Then the SMTPE allows for an additional displacement of +1/2 or -1/2 frame from there.

In that case, the sound begins position of A and C are both correct (and I expect, anything in between is considered to be acceptable), but the reference distance is wrong.

What's the reference in my schema? I have put a Visual POP 48 frames before FFOA which is not questionable, and a vertical white line 20 frames before visual pop because it is the position indicated in standard Academy TAIL. Dolby replied to me that for Dolby the right position is C and that it correspond to the SMPTE indication, but SMPTE count from 1 instead of zero (?!).

[Simone Corelli]

In that case, the sound begins position of A and C are both correct (and I expect, anything in between is considered to be acceptable), but the reference distance is wrong.

Marcel, if A and C are both correct for you, and also any value in between, why not choosing B as the ideal answer, and A and C as tolerated?

[Elia Orselli]

Sorry but using google translator I don't understand "I miss the all of the above option"

Marcel means «Lo leggo come un quiz. Però manca l'opzione "tutte le precedenti possibilità"»

[Simon Wyss]

In my opinion projectionists owe exact thread-up to everybody who has worked on a film before them. As a technician who has synchronized hundreds, thousands of hours of image and sound on Steenbeck, Moviola, Prevost, Schmid, and other facilities I can get very angry at ignorance destroying my efforts. Today’s TV is a huge deception in that respect. Sound almost always comes early, often by two frames or more.

Also projection speed should be correct. I find it unacceptable, if a movie produced at 24 fps is presented at 25 or vice versa. Even worse is what has been done to silent films and still is. Cinema is a technical phenomenon, so let’s master it. Crystal speed control with projectors is needed!

[Leo Enticknap]

Even worse is what has been done to silent films and still is.

Many if not most silent films were made in the absence of consistently applied technical standards determining the frame rate for shooting and projection. Often they were shot at one frame rate, with the expectation of being projected at another. Different shots within a movie were frequently taken at different frame rates. Some frame rates in shooting are physically impossible to reproduce in conventional projection (e.g. The Birth of a Nation, most of which was shot at 11-12 FPS).

Name me even one moderately well known feature made between around 1910 and 1925, and I could likely find you long running arguments between professors, archivists, and silent movie geeks as to what the "correct" projection frame rate should be, even though the correct answer is that there isn't one - just conflicting, informed opinions.

[Kenneth Wuepper]

One of my fellow projectionists at the Temple Theatre was a news photographer in the silent era in Chicago. He told of the difficulty of constant cranking in tense situations. The exposure was also a function of the cranking speed. He said that seeing some of his footage in the theatre was quite shocking as the projectors were also hand cranked back then. Bill Shepherd was a very fun person, indeed.

[Simon Wyss]

There is a speed standard, note is meaning to say still in force, as agreed upon by the signing members of the 1907 and 1909 Paris conventions of film producers. The frame rate of projection should be 1,000 per minute. The taking speed, however, has been propagated as 60 ft./min. Irritations were there since the beginnings for instance through the Edison-Dickson films which had been shot at 46 to 40 fps. The Latham Eidoloscope allowed to lower speed without flicker to about 12 fps due to its four-to-one ratio gearing between main shaft and shutter shaft but it is a wide film apparatus. A general speed increase took place with the cinemas after WWI, Don Juan of 1926 and The Jazz Singer of 1927 run at 22 fps. Vitaphone shorts run at 24 fps already in 1924 when Bell & Howell made 1,000 ft. magazines available to their Standard camera.

[Gordon McLeod]

Simon said "projection should be 1,000 per minute." hmm that would be impossible. When ERPI was determining the speed for sound they took the average that was being projected in Chicago first run theatres and that was 24fps. If that was the average then some were running far faster than that

[Tony Bandiera Jr]

Simon said "projection should be 1,000 per minute." hmm that would be impossible. When ERPI was determining the speed for sound they took the average that was being projected in Chicago first run theatres and that was 24fps. If that was the average then some were running far faster than that

Umm, no he is correct. What he said was "The frame rate of projection should be 1,000 per minute."

At 24 fps that equals 1,440 frames per minute.

1,000 Frames per minute is a rate of.....wait for it.......... 16 fps. (More precisely 16.6666666667 fps.)

Not only possible, but a long standing "standard" for silent film projection.