Transmitting in the blanking interval for broadcasting teletext

Question

Transmitting in the blanking interval for broadcasting teletext

sijanec opened this issue 4 years ago · comments

Anton Luka Šijanec commented 4 years ago

Hello!
I am very amazed by your project and I've been wondering if it would be possible to transmit in the blanking interval and thus transmitting teletext? As per https://en.wikipedia.org/wiki/Teletext#Data_transmission, I see that it uses 296 bits per line for data transmission. Would it be possible to output 296 bits of data per line? I see you mention in the video that the resolution can get up to 232x220. Would that mean that there is not enough "pixels" to represent each bit? What about the lines? Since NTSC has 525 lines maximum and channel3 esp8266 broadcasts way less lines, would teletext even be achievable?

CNLohr · Answer 1 · Mon May 04 2020 00:28:46 GMT+0800 (China Standard Time)

It absolutely would be possible! The problem is I didn't have any TVs that supported teletext or closed captioning. You would need to modify the NTSC generation code, but it wouldn't be too hard to swap out the "do nothing" for "do something interesting"

Anton Luka Šijanec · Answer 2 · Mon May 04 2020 04:15:02 GMT+0800 (China Standard Time)

Thank you very much for the answer! V V ned., 3. maj 2020 ob 18:28 je oseba CNLohr <notifications@github.com> napisala:

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It absolutely would be possible! The problem is I didn't have any TVs that supported teletext or closed captioning. You would need to modify the NTSC generation code, but it wouldn't be too hard to swap out the "do nothing" for "do something interesting" — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#24 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AKFM2EVWRFDBNH6AKXYV7W3RPWLUTANCNFSM4LVUGYIQ> .

Luminxa · Answer 3 · Sat Jul 11 2020 09:55:08 GMT+0800 (China Standard Time)

did you ever get teletext working? i would be interested in this..

Anton Luka Šijanec · Answer 4 · Sun Jul 12 2020 01:55:57 GMT+0800 (China Standard Time)

I realised I don't have teletext on my CRT TV so no, unfortunately I did not try to do it.

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On Sat, 11 Jul 2020, 03:55 Luminxa, ***@***.***> wrote: did you ever get teletext working? i would be interested in this.. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#24 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AKFM2EWRXSTBVJ2PPBULNMTR27BAPANCNFSM4LVUGYIQ> .

Ruchira Hasaranga · Answer 5 · Tue Jul 28 2020 19:52:14 GMT+0800 (China Standard Time)

teletext require PAL right?

Anton Luka Šijanec · Answer 6 · Thu Jul 30 2020 01:25:14 GMT+0800 (China Standard Time)

although the implementation differs from analogue video format, ntsc versions have also been created. see https://en.m.wikipedia.org/wiki/Teletext

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On Tue, 28 Jul 2020, 13:52 Ruchira Hasaranga, ***@***.***> wrote: teletext require PAL right? — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#24 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AKFM2EV24EALGPTEG2VMQW3R523XZANCNFSM4LVUGYIQ> .

CNLohr · Answer 7 · Fri Aug 14 2020 17:35:04 GMT+0800 (China Standard Time)

I don't have any way to receive it so I can't write it. Sorry.

CNLohr · Answer 8 · Fri Aug 14 2020 17:35:18 GMT+0800 (China Standard Time)

I'd appreciate it if someone else did it though