3

Is it possible to connect the unmodified video output from an Apple 1 and Apple II (with their non-standard/our-of-spec NTSC sync pulse levels and/or timings) to a (currently in-production and commonly available) flat panel television set, and get a good image? If so, what connectors, converters, and cables (etc.) might be needed?

(I’ve been told that many of the generic composite-to-HDMI (etc.) converters either refuse to recognize the input from an Apple I or Apple I replica circuit board, or produce unstable output.)

  • Not exactly the answer, but I have a 28" Visio (vizio.com/e280b1.html) with the NTSC composite signal from my vintage Laser 128 plugged into one of the 3 component inputs (luminance? I cant remember). It provides a very clear black and white picture but no color as I have it wired. – Geo... May 31 at 16:26
4

Most CRT-based television sets sold in the US will accept any combination of horizontal sweep rate that's within a few percent of 15.75kHz and vertical sweep rate that's within a few percent of 60Hz, with any arbitrary phase relationship, even though the FCC has for many decades required that broadcast stations output signals that are within a tiny fraction of a percent of 15,734.27Hz and 59.940Hz, respectively, with a precisely-specified phase relationship. Electronically, it was easier to make a set with a timing reference that might deviate from the ideal by 5%, but then make the set accept anything within 8% of that, than it would be to design a set which would know or care if the input signal was within 1% of the specified ideal.

Many if not most home computers and video games in the 1980s generated video with horizontal and vertical frequencies that were a percent or two away from the ideal frequencies and lacked the FCC-mandated phase relationship, since doing so was often easier than matching the specifications precisely, and because for various technical reasons doing so could improve the appearance of the computer's output on television sets of the era.

If the person who designs a digital television set wants to support 1980s computers, it would not be hard to make the unit give a better picture than a 1980s television. Many television sets, however, make simplifying assumptions about the incoming video signal and will produce an inferior picture (or in some cases no picture at all) if those assumptions don't hold.

Getting the best flat-screen picture from vintage electronics requires using a television set whose designer was interested in supporting such devices. Unfortunately, I've never seen support for such equipment regarded as a marketing feature. Some sets work well and some work poorly, but I've not found any way to predict whether a particular set will work with a particular device other than by trying it out and seeing what happens.

  • 3
    In a modern flat-panel TV, analogue inputs are handled by off-the-shelf decoder chips, so there really much for TV designers to do other than choose a chip. These chips are usually designed for the worse case of a VCR, where the timing is often way off. The biggest problem seems to be the "240p" problem, where every interlaced field has a even number of lines. Most chips seem to designed to handle this, but many TV seem to choke on it anyways. – Ross Ridge May 30 at 15:58
  • @RossRidge: I would have expected that modern television sets would simply feed the incoming signal into a pipelined ADC and then use software running on some otherwise-idle processor cores to decode sync and chroma. The level of CPU horsepower required to take a stream of 14,381,818 samples/sec and turn it into watchable video is less than the level required to handle streaming HD, so I'm not sure what benefit hardware decoding would offer. – supercat May 30 at 16:43
  • Sorry, not an answer to the question. I don't want to connect to a CRT, but to commonly available (not hand selected) LCD & OLED TV sets, via dongles if needed. Is that possible? – hotpaw2 May 30 at 17:06
  • Aside from a being a cheap off-the-shelf solution that just works, these chips incorporate a lot functionality like HD support, MUX'ing multiple analogue inputs, format detection, 3D comb filtering, time-based correction, colour space conversion, and so on. They're sampling at frequencies like 170 MHz and automagically converting the video into the same format as HDMI decoders output (which may also be integrated into the chip.). See the ADV7844 for an example of one the more feature rich decoders: analog.com/en/products/adv7844.html – Ross Ridge May 30 at 17:15
  • @RossRidge: Where would television sets' media-player functionality fit in? What about HDCP? – supercat May 30 at 17:40

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.