Dreamcast @ 1080p

I think your missing what I am trying to say and my explanation is not the best and is confusing you. My TV scales the VGA input resolution of 640x480 to the native display resolution of the TV which, is 1080p. It does not stretch the 4:3 aspect ratio to 16:9 of 1080p. Yes there are zoom functions and stretching options on my TV but it does not stretch and fit to 16:9 so there are always black bars either side of the screen. This is why I wanted to use the AT-HDVIEW or my receiver to do the upscaling...

Ted.

 

This is actually what most people want. Black/Gray bars instead of deformed image. But every TV I've seen allow you to stretch 4:3 to 16:9 ... You're sure yours doesn't?

 

My TV supports a couple of wide mode functions but it does not fit entirely to the 16:9 aspect ratio when viewing in PC VGA. Some games I am okay with 4:3 and actually some games look their best at that aspect ratio whilst there are others I much prefer stretched properly to 16:9. Scaling through the receiver quickly gives me the best of both worlds at the touch of a button...

Ted.

 

It's actually 720x480, not 720x640. As far as the non-square pixels go.... I'm not sure. Tomorrow I'll test some stuff out and check that.

 

It doesn't have square pixels, they're 10:11 like DVD/anything else following BT.601. Any illusion of square pixels is the result of interpolation.

Graphics (computer) oriented VGA -> HDMI converters probably work very similarly to your typical LCD panel--they lock onto and sample at (between) standard pixel clocks. This works well for computer graphics which have necessary high harmonic content (to give discernible pixels) thus are impractical to anti-alias and resample. They shouldn't work well however for the DC by which using a TV format should have a reconstructed video signal (meaning there are no "pixels" anymore, just a 13.5 MHz video signal which may only depict "pixel constructs" within the confines of the bandwidth).

 

That what I though, and 32:27 for 16:9 display. I always liked that kinda trick since I've encountered it ripping DVDs.

I'd have though that it'd actually be better to re-sample a more smooth analogous signal (TV format) than a more sharp one (Computer VGA) because it'd produce less aliasing artifacts. i.e. the interpolation is already kinda done by the analogous nature of the signal (natural sinc interpolation), whereas if the signal had strong high freq content it'd basically be quantized and require algebraic interpolation.

 

Teddy Rogers can you upload some pictures ?
Also what's the cheap scaler you bought (the first one)?

 

It would under normal sampling circumstances, but if the converter can lock to the source and sample between pixels, it's effectively a lossless A/D converter (apart from quantization noise). With the reconstruction filter, or an input anti-aliasing filter you'd lose the pixel boundaries and get group delay noise. That's what you'd want if it resamples/undersamples SMPTE at VGA (which it might), but could it sample SMPTE at SMPTE rate, why lose information if you can losslessly reconstruct the DAC code? I think this method is really beneficial for fixed-pixel displays since it completely prevents aliasing during sampling.

 

I'm confused, I feel like you agree with me and not at the same time...

I'll recapitulate what I understand:
- Cheap VGA2HDMI converters are probably aimed at old laptops with no hdmi-out and so they're engineered for VGA signal with a lot of high frequencies (so that pixels aren't blurred on beloved old CRT monitors)
- The DC outputs a TV format (SMPTE?), which doesn't have that sharpness, instead it's a more contiguous/smooth signal that approximates pixels but that still got infos "between" them.
- This should allow to re-sample TV format to another one quite well, as the physics does great analogous interpolation for you there within the output/cable/input bandwidths. (Basically fourier/sinc filtering, rather an approximation of it given bw limitations)
- Your last post got me confused.

I don't know much about broadcast, but I'm somewhat good at math and stuff, so don't be afraid to get technical.

Thanks again!

FG

 

I'm not sure how else to explain it, I'm not a mathematician or signal processing expert. In normal cases when you're resampling a signal from one Fs to another, then you want to completely band limit it to below Nyquist to avoid aliasing, but you can skip that if you already know or can figure out precisely where each discrete sample lies in order to directly sample the impulse. Since VGA converters can "cheat" and get around the sampling theorem by synchronizing to the source pixel clock, you get a better digital signal quality for doing so, it's as if you have infinite bandwidth because it's completely alias-free being synchronous to the source. If you reconstruct the signal first by filtering it to make it continuous, you no longer have the time-domain precision of discrete impulses to sample. Well, unless you have a brick-wall filter I guess.

Basically my point is that a DC signal would benefit from the full harmonic bandwidth of an un-reconstructed link because the harmonics make for sharp pixels in computer graphics which are probably appreciated for anything but natural video. If the intent is to view this video on a 1080p fixed-pixel display, I'd prefer to have an alias-free 720x480 pseudo-digital video source since each pixel is probably a valuable data point for the TV's interpolation. If the DC has a reconstruction filter, it won't be close to a perfect brick-wall. Most likely it will suppress high contrast pixel patterns and intuition (no proof) tells me it will CAUSE aliasing in the VGA converter's case because of its non-ideal stop-band for the sample rate. I believe if the converter decides to sample it as 640x480 or something else, there will even more aliasing (though of course not as much as there'd be if there were no reconstruction filter since entire impulses could be missed by the ADC). The VGA converter would have to oversample to suppress aliases in this case, and I don't believe that's in their nature since typically their goal is to recapture discrete computer graphics back into an ideally identical pixel stream.


Bottom line: if DC has a reconstruction filter which as a TV device probably does, I think:

-viewing the signal on a graphics-oriented VGA converter will have aliasing

-viewing the analog signal on a CRT monitor may look sharper since the harmonics won't be fully suppressed

-viewing the analog signal through a conventional video digitizer with anti-aliased input will be nearly alias-free, but won't have the sharpness that some people might expect (which is technically an unfaithful reproduction of the signal)

 

Sorry for the late reply. What pictures/photos are you after?

One of the VGA2HDMI adapters that I bought off eBay was similar to this...

http://www.ebay.com.au/itm/Blanc-Mi..._Câbles_audio_adaptateurs&hash=item35d1f0fa22

Ted.

 

I've been searching for days to get my Dreamcast working on my Samsung TV at 480p. I have a Samsung LE27C530 HDTV, which from what I've read, will not accept the Dreamcast's 480p VGA signal despite having a VGA port. Really annoying. I've just bought online a Dreamcast VGA cable which will work on my 23" computer monitor (hopefully), but probably not my Samsung TV. The idea though is to have my Dreamcast on my TV. I am not interested in a VGA to HDMI converter to improve the resolution as I know that my TV will convert the signal anyway, but I am considering one to solve this problem.

My Samsung TV has RGB SCART, which I am currently using on my Dreamcast, and I've thought about a SCART to HDMI upscaler, but what's the point when the TV is already displaying the SCART feed fine.
I've thought about VGA to component converter, but then that's not maintaining best quality. So I'm left with (if my VGA cable will not work on my TV directly) on finding a VGA to HDMI converter, which shouldn't produce any noticeable loss of quality.

But I'm at a loss on what to buy. They vary from £8.95 to hundreds. As I said, I just want a 480p signal through HDMI, if such a thing exists? I saw someone earlier in this thread said something on these lines. Ie, let the TV do the upscaling, not the box. Though I'd have no idea on how to make the box do that, and not upscale. (The cheap £8.95 box has a transfer rate of 1.65Gbps, which is less than the more expensive ones costing hundreds where I've seen one that has a transfer rate of over 6Gbps.)

I still live in hope my Samsung TV will accept the VGA signal, and the problem will be solved, but I doubt it... any thoughts?

 

The hammerhead vga2hdmi converter do what you want. I got one and it gives 480p over HDMI. Clones are fine too. I can't give a link as I'm on my phone. It's around 50$.

 

I've found one thanks. Looking forwards for some 480p Crazy Taxi and Daytona (when I get a copy).

 

I got that adapter and my Dreamcast VGA cable. Works great. Excellent picture, and no lag. Surprisingly, my 5 Series Samsung TV works with just the VGA cable, however, colours are washed out in comparison through the adapter and HDMI or RGB SCART. Adjusting the colours on the TV doesn't produce enough of a result to improve the colour much. So it looks l'll go with the adapter and HDMI route, despite the expense. My search around the internet on Dreamcast VGA showed that Samsung 5 Series TVs from around 2009 (mine is 2010) would not work with Dreamcast VGA despite having a VGA port. That was not true for my TV.