Linear (LTC) Timecode sync

DillTheKraut

Dear eight,

the LTC is a digital timecode like mtc (Midi Timecode) but encoded in an audiostream. This makes it easy to transport and distribute it to different systems, as it just needs to be connected with standard audio hardware and can be added and synced to audio and video streams on an extra audio channel of the footage.

As far as I know, there is no possibility for adding cue signals directly into the timecode signal. Isadora (v2) it self doesn't recognise LTC anyways. As far as I understood the new v3 will support it.

Solution:
Depending on your System (Windows/ OSX) there are software tools, recognising LTC and translating it to MTC. For OSX I like Lockstep https://figure53.com/lockstep/ .
MTC then can be recognised by isadoras MTC-reader actor. Combined with the timecode comparator you can do a MTC based trigger.

DillTheKraut

@eight said:

beside Isadora, will be fed into the conductor's ear

This would be a really bad idea, as SMPTE specific LTC Timecode is a digital signal and will hurt your ears badly! You should always be shure, not to mix this signal with a PA or any other open audio output with speakers or inears!
The conductor will probably be served with a 'click', wich is a rhythmic sound like a metronome, sometimes with two or more different pitches to separate the first note of the bar or the beginning of a new part. This will be played separately synced to the LTC feed. It would be very unsafe to use this for triggering anything in Isadora and I never heard of using it for triggering any system!

Here you can generate a wav file with SMPTE LTC and just test everything...

http://elteesee.pehrhovey.net/

~~Attached you find a LTC wav with one minute TC.~~ (Seems as I can't upload wav files!?) You can play this with any audio player, BUT be sure to lower the volume of your speakers to a minimum!!!

Juriaan

What we do normally when we are working with a conductor we use a Clicktrack. Basically a metronome that tells you the tempo of the file, it works quite well.

Regarding LTC,

Great if you wish to connect multiple hardware solutions with eachother and keep them in sync, don't put it in people ears ! It will hurt them.

Isadora (2) doesn't has dedicated LTC support, like @DillTheKraut said use a convert app. You also have https://www.videotoolshed.com/... for windows / Mac for example that converts the LTC to MIDI Timecode that Isadora understands and work with.

eight

Thanks, guys, @DillTheKraut and @Juriaan. I've got Lockstep running and an LTC Timecode example running off http://elteesee.pehrhovey.net/... I also set up MIDI input, which recognizes Lockstep. However, I see no output from the MTC reader. Any thoughts?

And yes, you were right about the conductor. He gets a synched Click signal, not raw LTC timecode.

Thanks again.

Juriaan

You are currently on your Built-in Microphone. Basically Lockstep has to showcase that it is playing, looks like this

https://figure53.com/lockstep/ (The figure show that it needs to be green)

DillTheKraut

@eight

If you want to play the LTC audio file on the same device with lockstep, you have to route the audio out of the wav player software to a virtual audio out device, that is then listed in the LTC input drop down menu in lockstep. You can use rogue amoebas loopback https://www.rogueamoeba.com/lo...

Another possibility would be, to play the wav file from another device and connect the out to the audio input of the lockstep running device.
This would probably be the way to go when running your project setup, as the LTC signal will come from your audio department.

Be sure, to keep a propper but not to high level of the audio in volume. If it is to low, the LTC code might not be recognized. If to high, you might get drop outs because the audio will be scrambled.

Woland

@eight said:

In a musical show, I will be given a linear LTC Timecode signal, which beside Isadora, will be fed into the conductor's ear as well as the lighting board. What's the current state of using LTC Timecodes to switch a scene in Isadora? I understand that in the LTC Timecode, which is an audio signal, I could add my own tags (meaningful frequency patches). Then, theoretically, I could use a frequency watcher in Isadora, tuned for the inserted tags.

@eight , this is specific to you since I know that you're in one of the Isadora 3 beta-testing groups, but if you're being fed LTC and using Lockstep to convert it to MTC anyway, you could try using the Isadora 3's built-in MTC features to trigger things with timecode. There are details on how to use it in the downloads thread of the private Isadora 3 Beta forum section (to which you should already have access).

eight

@woland Thanks. I knew that LTC Timecode is supported by Isadora 3, but am not sure I could use it in the show that is going to be live in 2 weeks. What's the ETA for Isadora 3?

Woland

@eight

See Mark's answer here about the release date question. I didn't know your show was in two weeks, meaning the beta might not be a good option (though we do have two top-level beta-testers using the beta in a live environment, neither of them are using the MTC feature set for their work).

Juriaan

Regarding the stability of the current beta, it is okay. I had some minor issues while patching, during show it was stable. Personally I don't see why the Stable build is not good for now ? MTC Reader is also included in 2.6.1, and with a bit of clever patching you can patch around some stuff.

eight

@Woland and @Juriaan thanks again. Just a bit more info on how I was able to test this setup: TimeCode Clock -> SoundFlower Bus -> LockStep -> Isadora.

Woland

@eight said:

TimeCode Clock

Neat app! Thanks for sharing! Minus TimeCode Clock, that's the same workflow I use and suggest in my example files on the Beta Forum.

Woland

@juriaan said:

Personally I don't see why the Stable build is not good for now ?

Personally, I agree with you. I think the build is stable enough to run shows, but professionally I hesitate to recommend running a show on a beta build instead of a release build without adding the "do so at your own risk" disclaimer.

eight

Although I can get the MTC into isadora through Lockstep, there is timing issue. The input source is at 30 fps, but it seems Lockstep outputs 29,97 fps. It would be OK, if the marked timecode values were different from the source, but still reproduce. However, I get different values each time the same LTC signal is sent to me through Lockstep. Lockstep does not have the controls for the output FPS.

Juriaan

The most simple way to solve this issue is to ask your Audio engineer / Source of the LTC to output 29.97 frames a second.

Regarding your sync issues :

"LTC, perhaps surprisingly, does not include the framerate anywhere in its data stream. MTC, on the other hand does—to an extent. So Lockstep has to wait until it's received enough frames of LTC to be able to tell definitively what framerate is being received before it can safely start transmitting MTC. This can take as long as a full second, depending on where the timecode stream starts."

Bouke

@eight,

Please try the above mentioned LTC/MIDI reader. It can do 'true' 30 fps, either by auto-detect, or you can force set it.

(I'm the developer :-)
hth,
Bouke