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#21 | |
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Quote:
There are also the analog Cinergy ones included (just search for "hybrid"in that list), but you're right, they do not state if the analog part is actually supported or not. From some googling it seems to be the case at least for some of them, but you may be better off with an old Windows box if you choose to go down that route. Or maybe a VM with USB support. Last edited by chb; 25 April 2020 at 20:55. Reason: typo |
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#22 |
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Join Date: May 2017
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might be easier to hunt down an old CRT somewhere ... I will keep an eye open.
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#23 |
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Doesn't have to be CRT
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#24 |
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to decode and display a correct teletext signal, any TV set will do.
to test overscan modes, blanking intervals, timings ... a CRT is probably more forgiving and you have a more direct feedback. A flat panel will probably just go blank and/or give you error codes. |
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#25 |
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might still be interesting to use a raspberry pi to get and send the Teletext like Teefax and use the Amiga as the Teletext decoder.
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#26 | |
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![]() well - that does require additional decoder hardware for the Amiga. (and has been done before multiple times ... see hardware book and aminet ...) Last edited by Gorf; 26 April 2020 at 01:14. |
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#27 | |
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Quote:
The only TVs I have are large ones bolted to walls in rooms where I can't set up an Amiga. I might be able to get my hands on a small one to try this out though... The teletext decoding is forgiving enough that it works over RF so I think an Amiga in hi-res mode should be able to produce the bitmap. |
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#28 | ||
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Quote:
Quote:
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#29 |
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Going Completely off-topic I assume you can skip part if you don't have a Teletext TV and use the Raspberry to just display it.
And....... Apparently BBC is going to stop its Digital Red Button Teletext - they never did replace TeleText with a Good service ok we have the internet but on CeeFax you could display Headlines/New Flash and Sport Scores on Top of the picture and few other things that never got properly replaced. |
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#30 | |
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It is about broadcasting teletext signals FROM the Amiga onto a TV. Generate on the Amiga, send to video out, into the TV and decode it there! |
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#31 |
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Is the Amiga capable of Teletext?
Yes, it is ![]() https://www.pouet.net/prod.php?which=94736 They encoded Teletext data during vertical blank, awesome! |
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#32 | |
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Quote:
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#33 | |
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It is also possible to open the horizontal blank, I have already done it in the past: https://eab.abime.net/showpost.php?p...2&postcount=11 All the sync values are the usual untouched hardwired PAL ones. EDIT: the super-nice thing here is not the 'VB open' but the Teletext encoder! Kudos to losso ![]() Last edited by ross; 30 July 2023 at 23:37. |
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#34 | |
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Location: Sofia / Bulgaria
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Quote:
[ Show youtube player ] |
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#35 | |
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Quote:
About the audio, there could be an explaination: the core probably do not rightly emulate the differences for VERTB using VARVBEN. |
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#36 |
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@pandy71
Some technical details. The hardwired values for vertical blank in PAL are: start at line 0 (inclusive) and stop at line 25 (inclusive). In ECS and AGA you can decide to change those values (without touching anything about the sync signals!). So you don't have to create a custom video mode compatible with TV (it's not that trivial to do that), but simply 'extend' the available one ![]() Of course each device is free to behave differently in this regard (thus deciding whether to display video data or interpret 'digital data' for 'other'). The PAL standard defines datas are valid only after 25 blank lines, OSSC instead requires only about 10/11 lines (from here my 408x302 pixels image). TVs with Teletext decoders as early as line 8 can interpret digital data. There is a reason for this: A valid PAL frame is defined by 5+5+5 half-lines composed by pre-equs/serrations/post-equs signals. As you can start with an half line difference (to define long and short frames, ie interlace) you need at least 0.5+7.5 video lines. Starting counting from 0 you have that the first valid line for any type of output data is line 8 and it is exactly the one used in this case. This perhaps means that OCS too can manage to do the same since the Agnus y counter can be manually programmed, but we are probably going to open a big can of Worms ![]() |
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#37 | ||
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Quote:
This is also quite interesting as it should allow Amiga to for example produce correct WSS and signal it to display. Asking because it would be interesting to me to transmit PCM data in VBI to external DAC over videoport. And to confirm - just checked EN300706 so normally lines "from 6 to 22 and 318 to 335 may be used to carry Teletext data packets" but standard allow use all video lines "except those occurring during the field synchronization and equalizing pulse periods" so technically to get TXT on screen you may transmit it in visible part of video. with some remarks: Quote:
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#38 |
Amiga user
Join Date: Nov 2008
Location: Sofia / Bulgaria
Posts: 477
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Any video link to this presentation:
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#39 | |
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For PCM signals I imagine that you have a regular frequency flux and therefore you could potentially fall on the (unusable) synchronisms/horizontal blanking part (or can you use spaced regular packets?). In experiments I was able to use at most about 204 out of 227 CCK/line for output data on OSSC. Probably some devices could do a little more but then we collide with the impossibility for Agnus to use all the cycles for the bitplane fetch. But I have no idea what you want to do so I wouldn't know ![]() And beware: Amiga line counting is different from PAL standard counting. The hardwired 0 line is where the pre-EQ pulses begin (at start or half line position). In PAL you can see 311 or 623 because it count always as interlace and it start from '1' by serration pulses from first field.. Amiga instead always counts from 0 and restarts from 0 also from the second field (one long and one short). So to all intents and purposes the first line after the post-EQ on the Amiga is line 8. The same goes for when you calculate line '25'. |
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#40 |
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