35mm and 70mm subtitle system

[Javier de Blas]

Hello everyone for the last month or so I've been working on a solution to sync subtitles with film. The whole thing started because when warner brothers gave us the 70mm copy of Interstellar they didn't (neither want to make) dts subtitles for the xd10. Plus it came with the english and german soundtrack, so dubbing wasn't an option either.
I've created this little system that can decode the time code of the film, pass it as serial and sync and display subtitles coming from an srt file with it.
Obviously this is still a prototype, I'm still planning to make it more self content and neat looking, plus easier to use without touching code. But for know it's been working really great on our Interstellar screenings and I want it to share it with you guys.

https://youtu.be/qQnk6qZ19Hs

[Marco Giustini]

Interstellar was DTS-ES?

[Javier de Blas]

Interstellar was DTS-ES?

There's no mention of dts-es on the disc. Plus I don't really know how dts-es works. I understand that it can provide an extra back center channel with matrix sound. But the xd-10 and 6D only output 6 channels through the analof output that we connect directly to the cinema sound processor, so I don't where that extra channel would be coming from. Maybe and extra device like the dolby SA10 for dolby digital ex? I don't know.

[Marco Giustini]

5-digits serials were indicative of an ES/EX track. The DTS-ES would also read timecode and, when detect a 5-digits serial, would automatically enable ES processing. You'd usually see a DTS-ES logo on the disk though.

You could also add an SA10 to it - but you would need to have your own automation. Dolby Digital had an EX Flag in the stream - which was usually poorly implemented with some reels having it enabled and others not.

Unless DTS-ES was 5 digits over 60k?

[Josh Jones]

Hello everyone for the last month or so I've been working on a solution to sync subtitles with film. The whole thing started because when warner brothers gave us the 70mm copy of Interstellar they didn't (neither want to make) dts subtitles for the xd10. Plus it came with the english and german soundtrack, so dubbing wasn't an option either.
I've created this little system that can decode the time code of the film, pass it as serial and sync and display subtitles coming from an srt file with it.
Obviously this is still a prototype, I'm still planning to make it more self content and neat looking, plus easier to use without touching code. But for know it's been working really great on our Interstellar screenings and I want it to share it with you guys.

https://youtu.be/qQnk6qZ19Hs

I assume you had to create a custom *.SRT to match the time code of the film, or does your software handle the offset? I would love to learn more about how this was implemented. Nice work!

[Javier de Blas]

I assume you had to create a custom *.SRT to match the time code of the film, or does your software handle the offset? I would love to learn more about how this was implemented. Nice work!

No, the whole idea is to use an standard srt file of the picture, the one distributors give you in the best case scenario or taking it from a dvd, blu ray or the internet in a less error proof case (specially intro logos, are they hell for sync or what).
With the length of the reels reeded on the dts discs I make a time list to compensate, since time is based on reels and not complete feature on dts (and dcp actually) while an srt is based on the whole running time.
I would like to make a better version in the future and be able to sell it. One of the big selling points it would be that once a film is loaded with the compensation times for each reel you could load a generic srt file of any language all by yourself.
I have tried to get this compensation times from the dts discs automatically but they are a mess. Most discs have different amounts of silence and beeps at the beginning and end so taking the whole length of the reel is no good and trying to cut always the same time from the start and end won't work since each film and reel is different without apparent pattern.
But well, I'll keep posting the next versions of it so I can have your opinions to improve it.
For now it's just a really bare bones prototipe.

[Marcel Birgelen]

First of all my complements for the idea and execution. But please, get a new camera and a new cameraman.

From the blurriness I've seen, I've seen something like an Arduino or other microcontroller kit that's getting the serial output from a DTS timecode reader. Do you have one reader in this system or two? The Arduino signal is then fed into a notebook and the notebook runs a little program rendering subtitles on a black screen, sourced from an SRT file and matched up with the timecode. Then this image gets projected over the 70mm image using a digital projector.

[Javier de Blas]

First of all my complements for the idea and execution. But please, get a new camera and a new cameraman.

From the blurriness I've seen, I've seen something like an Arduino or other microcontroller kit that's getting the serial output from a DTS timecode reader. Do you have one reader in this system or two? The Arduino signal is then fed into a notebook and the notebook runs a little program rendering subtitles on a black screen, sourced from an SRT file and matched up with the timecode. Then this image gets projected over the 70mm image using a digital projector.

It's a custom circuit a designed plus an ESP32, the time code is sent in parallel to my decoder and the xd10 at the same time with just one reader.

[Michael Zarits]

5-digits serials were indicative of an ES/EX track.

To be precise, SN 32768-65535 is detected as DTS-ES.

[Marcel Birgelen]

It's a custom circuit a designed plus an ESP32, the time code is sent in parallel to my decoder and the xd10 at the same time with just one reader.

Is the output a clean RS232 serial stream or is it something else? And are you simply repeating the signal?

[Javier de Blas]

Is the output a clean RS232 serial stream or is it something else? And are you simply repeating the signal?

It's a serial stream indicating the frame, time, film id and reel id. The pc program reads the clean digital serial data and syncs the subtitles with that.

[Ryan Gallagher]

Love it. What did you use to "split" the the DTS serial... was it a fairly passive method? I assume so considering change-over setups just call for a passive Y cable.

This is pretty straightforward with a platter and a single DTS reader... for a changeover system, are you tapping/splitting the serial data somewhere that could be done after the Y cable for two readers?

How does your effort so far handle (or not) any loss of timecode, such as a poorly executed changeover or film break... does it easily pick up once time code is resumed?

Separately, on your setup. I wonder about improvements to avoid obliterating the gorgeous film blacks by overlaying the digital black (although Laser may not be as much a problem). Did you make any physical masking cards/cookies to limit the contrast damage to the lower 1/3? I expect for overlayed subtitles one would not have to run digital lamps at full DCI brightness levels either (although that assumption might be wrong since you are "competing" with an existing image). In a perfect world there would almost want to be a subtitles "screen" below the film screen... think of an opera super-titles screen perhaps, but may not have to be that big in a much smaller room.

Once you are in that territory perhaps a smaller projector is the subtitles tasked one as with so many of the other solutions out there. This potentially saves lamp hours and avoids "altering" the 70mm image quality with overlays.

There is a company here in town that makes nearly "black" ambient light rejecting screens... (Screen Innovations / Black Diamond series). I've always thought a custom shaped rigid framed one of those would make an excellent super-titles screen (or subtitles here).

[Ryan Gallagher]

Tangent. Something like this gives a humor inclined projectionist way too much freedom. Case study:

Star Trek VI was released in 70mm:

Star Trek VI has a fandom generated Klingon Language SRT ( https://zrajm.org/st6/ )


But seriously... in multi language regions you could do interesting things like render dual language subtitles too, 3 language presentations if you include the ST native language.

[Jim Cassedy]

Very nice! I'm always very impressed when someone comes up with a home-brew solution
to a technical projection problem. Good work! What I often wish I had here was a remote
time-code display for XD-10. (but I should hook you up with one of my film-maker friends
who built his own Steadicam™! ) lol

[Javier de Blas]

Love it. What did you use to "split" the the DTS serial... was it a fairly passive method? I assume so considering change-over setups just call for a passive Y cable.

This is pretty straightforward with a platter and a single DTS reader... for a changeover system, are you tapping/splitting the serial data somewhere that could be done after the Y cable for two readers?

How does your effort so far handle (or not) any loss of timecode, such as a poorly executed changeover or film break... does it easily pick up once time code is resumed?

Separately, on your setup. I wonder about improvements to avoid obliterating the gorgeous film blacks by overlaying the digital black (although Laser may not be as much a problem). Did you make any physical masking cards/cookies to limit the contrast damage to the lower 1/3? I expect for overlayed subtitles one would not have to run digital lamps at full DCI brightness levels either (although that assumption might be wrong since you are "competing" with an existing image). In a perfect world there would almost want to be a subtitles "screen" below the film screen... think of an opera super-titles screen perhaps, but may not have to be that big in a much smaller room.

Once you are in that territory perhaps a smaller projector is the subtitles tasked one as with so many of the other solutions out there. This potentially saves lamp hours and avoids "altering" the 70mm image quality with overlays.

There is a company here in town that makes nearly "black" ambient light rejecting screens... (Screen Innovations / Black Diamond series). I've always thought a custom shaped rigid framed one of those would make an excellent super-titles screen (or subtitles here).

Indeed I used a simple Y cable to send the serial data both to my decoder and xd10. But there would be different possibilities on how to connect both a platter or changeover system. But before that I have to explain that my decoder does not only decode the dts signal but also cleans it to a perfect digital level before giving it to the ESP32. For example in my home set up, where I have my dts 6D connected to the dts reader with a very poor quality 10 meter serial cable; the xd10 does not pick up the time code properly, it goes off a lot (ironically the 6D handles it perfectly). So when I connected the time code to the "cleaner" part of my circuit and gave that directly to the xd10 it worked perfectly with no losses whatsoever.
So, knowing that there're several possibilities. In the simpler hand (changeover system wise), I could just make a cable that connects to both projectors and has two outputs, one for the dts processor and another to my decoder. What I thought it could be better than that is to do the same thing but having an input and output db9 on my decoder. So you can connect the cable you already have to my decoder and connect a regular short db9 cable between my decoder and the dts processor. That way I could just pass the signal passively when my decoder is off and have the option to send a cleaner signal to the dts processor when its on.
In case of a platter system the second option with in and out on the decoder would be the same and in case of using a cable the regular Y cable used on changeover systems would work.

In the matter of loosing timecode the code has an "in sync" and "out of sync" functionality where it does the follow. In the "in sync" mode, it is receiving the time code perfectly and it is just playing the subtitle lines inside that time. In this mode it saves the speed of the projector referring to the frames received by the time code. It's a little bit messy since dts is actually 30fps not 24fps (that was a headache). But it's just saving a multiplying factor for going at the perfect 30fps it suppose to. That way in the "out of sync" mode, when it's not receiving the time code properly. Starts running an internal clock at the speed measured before from the last time code received. So it keeps playing even if not receiving. In any case, that functionality has not been used in any of the screenings I've made until now (40 or so). It triggers for a fraction of a second some times on splices and things like that (just in two occasions on this intersetellar copy where the film is badly scratch). But they are so little that I think that even with the "out of sync" mode it would work alright.
A poorly executed changeover wouldn't be a problem whatsoever, since it would be receiving the time code any way, from sooner or later on the film, and it would project the subtitle of such time.
And yes, the change between "in sync" and "out of sync" mode is seamless to the viewer, even so, it is notified on the serial output.


About not altering the 70mm presentation with the digital projection, it's been an odyssey (get it? hahaha).
At first I tried to use a little home projector, but it was simply not powerful enough to much the 5000w xenon of the 70mm, in bright scenes it was simply unreadable. That's why we used the laser projector instead. What I dis was, first, set the digital projection as low as possible. Then create a cardboard masking attached to the window of the booth (you can see it a bit in the video). As a last step I rendered the subtitles yellow and added a yellow masking to the cardboard, so the rest of the light would be more blocked. And you may ask now. Why there's no such filter on the video. Well, universal wanted white subtitles for the Odyssey, so we had to remove the yellow filter. I can't win them all.

Also, I forgot to mention, the idea of a subtitle screen was also mentioned, but the cinema did not want to do it. (At least we have masking on the screen to get perfect 2.20 in an 2.35 screen, a lot of cinemas don't )


And yes, I love Star Trek, a lot. I would be the hooligan projectionist screening Star Trek 6 with Klingon subtitles. Absolutely! It would be fab.