If anyone wants one I have a number of Hedghog PCB's for sale. The cost is 7 euro which includes UK postage.
Frank
That's a very generous offer indeed.
I have been ask a few times if I would supply complete Hedghogs but as I have said right through this project I am not in a position to do that.
Forum member Freya(Stephen) has stepped into the breach as he has told me that he is willing to supply complete Hedghogs.
So anyone looking for a complete one, can get in contact with him.
Frank
Well done Stephen. He's an experienced engineer and will do a good job.
Hi Jeffrey
I am glad Stephen stepped in. There are many that would like one but for one reason or other cant build one. Now they have an opportunity to have one if they wish.
I think it is really great that this service is been provided.
Frank
Early on in this project the inclusion of conversion from 16:9 to 4:3/5:4 was discussed. At the time I did some calculations but decided to leave trying it until the end at which time I would know what resources I had left over. Well it sorta got forgot about. Well that was until forum member Doz built a converter and wrote a blog about building it (
here). In the blog he raised the question about 16:9 to 4:3/5:4 conversion.
So I decided to give it a go. It is a straight forward crop the beginning and ends off each line.
The results are shown in the photos below which show how the picture is stretched for the different combinations of input/output.
This is just the first stage. There is some tweaking to be done and some niggles to be got rid of.
I am glad now that I have those extra DIP switches
. I will be able to make use of them for this extra function. Both for the function itself and to select if it is available on the front panel or on a DIP switch.
Frank
I noticed this post regarding German 441 line TV:
https://www.vintage-radio.net/forum/show...ost1114281
It would be very simple to use the Hedghog hardware to do all that he's doing and much more besides. Including full conversion from 625 to 441. I doubt that any hardware mods would be needed, just changes to the VHDL.
Thinking even further, I can't see problems using the Hedghog hardware to convert to any other vintage standard. 405 line NTSC would depend on there being enough resources in the FPGA The decoder chip already provides Cb and Cr as well as Y. Just depends on having enough storage and processing to do the arithmetic. Deepending on how you do the sums, an NTSC coder isn't conceptually complex but does need several multiplications. The quadrature modulator needs 2 multipliers, though it may be possible to do it with one using multiplexing. Also need fixed coefft multipliers to get the U and V weighting. More may be needed to interpolate the U and V signals up to the output DAC frequency.
Frank en Jeffrey,
Would it be possible to "convert" the Hedghog to a standardsconverter for 625 to 567 lines?
The 567 line system basically is the same as the 625 line system, only having fewer lines.
Test patterns would not be required, and (at least in theory) the aspect ratio is 3:4.
Two frequencies have been in use during the 567 line period; both have a 4.5 MHz vision-sound distance and (as 625) FM sound and negative video modulation.
Baseband 625 --> 567 would be great already, since modulators are not the biggest problem.
I have 3 (restored) experimental Philips sets for the 567 line standard, and 2 home build ones (not yet restored).
I now have them working at 625 lines, but it would be fantastic to have them in their original state, i.e. 567 lines !
Jac
I forgot to mention: the 567 line standard is only B&W.
Jac
I can see no particular problems in making a 567 line output. Is there a document with the video and RF specifications for 567? The modulators can do just about anything. For many standards a single modulator can do both sound and vision but the combination of AM sound, 3.5MHz sound/vision spacing and +ve vision modulation was impossible with a single chip.
I haven't looked at Frank's VHDL but If you're designing for multiple standards I would have all the numbers for each standard specified separately from the logic.
This is a possible way to specifiy horizontal sync pulses with the numbers included in the logic. To change the standard you have to go through the code and change all the numbers:
HSYNC_START <= HCOUNT = 6;
HSYNC_END <= HCOUNT = 135;
if HSYNC_START then HSYNC <= true;
elsif HSYNC_END then HSYNC <= false
else HYSNC <= HSYNC;
end if;
This is a more general form. HSYNC_START_COUNT and HSYNC_END_COUNT are specified in a table of values for that standard. Possibly in a different file.
HSYNC_START <= HCOUNT = HSYNC_START_COUNT;
HSYNC_END <= HCOUNT = HSYNC_END_COUNT;
if HSYNC_START then HSYNC <= true;
elsif HSYNC_END then HSYNC <= false
else HYSNC <= HSYNC;
end if;
Or if you want switchable multistandard operation you would have a CASE statement. This would include all the numbers that change for different standards:
case OUTPUT_STANDARD is
when S405_50i =>
HSYNC_START_COUNT <= 6;
HSYNC_END_COUNT <= 135;
when S567_50i =>
HSYNC_START_COUNT <= 8;
HSYNC_END_COUNT <= 119;
when others =>
HSYNC_START_COUNT <= 6;
HSYNC_END_COUNT <= 135;
end case;
Please note that all the numbers I have used are pure fiction. I haven't bothered to do any sums to find out what they actually should be.
The standard names such as S405_50i can either be an enumerated type in VHDL or allocated as constants. This is an extract from a file called "general_constants.vhd" that I have included as a package in a library in some of my own professional designs:
constant S720_30p : integer := 12;
constant S720_25p : integer := 13;
constant S1080_48p : integer := 14;
constant S720_24p : integer := 15;
constant S525_60i : integer := 16;
constant S625_50i : integer := 17;
Because all of Frank's design is open source, anyone is free to experiment as they wish. Unlike the Aurora where the design is proprietary.