ITTS (DCC text) reimplementation

[Max]

@drdcc

Video 4566 Scorpions; only show 21 lines on the ITTS Box (same for the other commercially released albums that have lyrics info.
Video 4567 Supertramp Sampler ; will work on 2 and 21 lines on the ITTS Box and also on the DCC730/951
Video 4568 Kermit Sampler; only shows 21 lines on the ITTS Box
Video 4569 Sonos Sampler; will work on 2 and 21 lines on the ITTS Box, but will not show the lyrics on the DCC730/951

What about 1 line, is that supported by none of the tapes you mentioned? Could 1 line ITTS be the 3rd gen lyrics?

[drdcc]

Hi,
None of the tapes worked with one line. Even the Supertramp demo tape that does work with 2 lines AND on the DCC730 and 951.

What I do not understand is that the Sonos Sampler is the only commercial tape that also works with 2 lines and 21 lines (next to the Supertramp), but does not work on the 730/951.

[Jorn]

Will do, video of the itts in demo mode

[Jorn]

Here the video of demo 1

Digital Compact Cassette, ITTS - Demo 1 modes

[drdcc]

Thanks @jorn

[Max]

Thank you!

Only the artist name in the title overview and some styling has reserved1 1. No idea why, I will ignore it for now, as the rest are otherwise valid ITTS packages.

@Max

I already noticed something weird, bit 7 of the demo ITTS headers is 0 on some packages (I called it reserved 1), but it would have to be 1 to comply to the standard: “Default (must be set to 1 to identify the packet format according to this standard)”.

I am wondering if they are displayed or if it is some kind of internal comment.

For example is the final package “DEMO MODE_2 VIDEO ITTS BOX C.v.d.Bergh” being displayed?

Do commercial DCC releases also contain ITTS packages like that?

[Jac]

@Max

Now I know for sure, that it is not based on videotext in any way and is likely just using the OSD mode of the videotext IC

I’m pretty sure that’s how the ITTS box does it: by letting the microcontroller use I2C to use the OSD feature. I haven’t had a good look at how the MCU and the Teletext chip are connected, and I haven’t had a good look at the datasheet of the Teletext chip either. I wonder if there’s a limitation to where OSD text can appear, and if that’s why the text is so low on the screen; I think it displays the ITTS line 1-21 on lines 5-25 of the Teletext page (yes Teletext only has 24 lines but the display probably uses 1KB of memory which is slightly more than 40x25 characters).

@Max

I will need to think about how to store timing and at least volume of the audio to be able to store and use it synchronously. Maybe adding a custom extension to a container like ogg or mkv is the way to go, I am not sure yet.

I’ve been thinking of how to store a DCC dump, and I was thinking of just interleaving PASC frames with other data, formatted in some format that’s compatible with e.g. ID3 or something. But using an existing container format is possibly an even better idea. I wonder if those formats already accommodate ITTS? Maybe the folks in the MiniDisc universe already have a standard format for container-ing MD dumps with text information? We do have potentially more information to store though, I don’t know yet. Not all of SYSINFO/AUXINFO is ITTS.

@Max

@Jac I hope you don’t mind me ‘stealing’ this subject from you, without your groundwork this wouldn’t be possible.

No problem, and you’re welcome!

===Jac

[Jac]

Oh by the way I believe Matroska files that only hold audio should have the mka (not mkv) extension. Though you could argue that ITTS is video of course.

===Jac

[Max]

I spoke with someone on the #36c3 about implementing the graphics layer. He suggested using https://www.libsdl.org/ for the drawing. Seems to fit the purpose. He remembered DCC from his youth, but didn’t quite understand the spot in the market. Maybe he’ll join later.

And I spoke with a couple people about STM32 tooling and got the recommandation of discrete logic and another Microcontroller, quite like @Jac’s Propeller.

[Max]

What about demo 2?

[Jorn]

@Max Demo 2, has no function.

[Max]

Than it is oddly standard compliant, because a bit that should not be set for standard compliant ITTS is set.

[Jorn]

@Max, do no understand what you mean, can you explain in other words what you mean.

In the context, the ITTS has never been a consumer product, so in this case a switch is not always programmed/connected so no used.

[Max]

I extracted a copy of the demo ITTS packages from @Jac’s dump. Some of the so called packages have a bit set that is reserved which means they should be ignored. I guess this was supposed to trigger the other demo.

[Jorn]

Probably

[Max]

Could you capture it digitally or at least film it with more light, I am interested in the top and bottom empty space to fill knowledge gaps.

The standard suggests a normal character at least in the graphics mode as “12h × 10v pixels”.

Currently I am working with the idea of 480*360 pixel which translates to 40 characters per line and 24 lines, so where are 3 lines? Or do we have bigger left and right bars than 4:3. Could also be some kind of Overscan because outer pixels weren’t being displayed on analog TVs and this behaviour was adopted to this day.

@Jorn @drdcc Are you using NTSC or PAL?

[Jorn]

[Max]

Could be the reason why the demo does not work for @drdcc.
Can you record the demo again via direct capture or at least with the lights on that I can see the borders of the TV?

[Jorn]

[Max]

The ITTS demo is not fully ITTS standard compliant, it is such a mess, I am starting to understand why it did not take off.

FYI: The first prototype of ITTS display will be based on https://www.pixijs.com/ and thus browser-based, because PixiJS can directly draw text from a chosen font and resize it without the major headache of drawing sprites. I was finally able to sort out the resolution and font-problem.

The resolution really used in the ITTS-box is 480x420, this makes up 12px width and 20px height in 21-line mode with the 40 characters per line limit. Was super hard to figure out, but it makes sense in the end and can be scaled to higher resolutions relatively easily.

I chose the Inconsolata font, because it is monospaced and looks nice enough in this aspect ratio, here you can see a scaled preview of it this way:

If anyone wants to join my ITTS efforts, leave me a private message.