Compatible Colour NBTV on CD

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Compatible Colour NBTV on CD

Postby Andrew Davie » Thu Jun 07, 2007 4:28 pm

Attached are the official documents, sent to me by Klaas Robers, that document the format of the compatible colour NBTV system. I have permission from Klaas to post these, so I hope that this will open up discussion on the colour TV format and encourage more colour monitors to be produced.

I found the encoding to be quite ingenious, and it was a real shock to me to learn that I didn't really understand colour nearly as well as I thought I did.
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CD-colour standard.pdf
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Colour NBTV ver 7 okt.pdf
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Using 'naked' CD drives.

Postby Steve Anderson » Thu Jun 07, 2007 6:46 pm

The whole aspect of using the raw digital data from a CD drive is intriguing to me. I hooked up an old CD-ROM drive to two power supplies and to my suprise it played back a standard audio CD. (See pic).

There is nothing plugged into the rear 40-pin connector, only the jumper set to make it the 'master', although even that might not be needed.

What I have been trying to find out with extensive 'Googling' is the format of the 16-bit parallel data on the EIDE connector at the rear, so far I haven't got anywhere.

I presume that it's in 2's compliment form, interleaved left/right. But there's no clock output nor any way I can see of identifying which channel is which. All I can guess is this is the raw audio, complete with error-correction data.

Klaas, you might be able to help here.

Steve A.

Update...the 'Master/Slave' jumper isn't needed.
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CD 1.jpg
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Last edited by Steve Anderson on Thu Jun 07, 2007 7:02 pm, edited 2 times in total.
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Re: Using 'naked' CD drives.

Postby Viewmaster » Thu Jun 07, 2007 6:53 pm

Steve Anderson wrote:What I have been trying to find out with extensive 'Googling' is the format of the 16-bit parallel data on the EIDE connector at the rear, so far I haven't got anywhere.
Steve A.


Is this any help?....scroll down the page.

http://en.wikipedia.org/wiki/Advanced_T ... Attachment

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Re: Using 'naked' CD drives.

Postby Steve Anderson » Thu Jun 07, 2007 7:07 pm

Viewmaster wrote:Is this any help?....scroll down the page.

http://en.wikipedia.org/wiki/Advanced_T ... Attachment

Albert.


Yes, it was help, I came across it also, but it's more about how the data stream is organised which I'm having trouble with, not so much the hardware connections. Thanks for the effort, it is appreciated.

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Postby M3DVQ » Thu Jun 07, 2007 7:35 pm

the 40 pin connector is IDE, for data... will this contain the original audio data? :?
if the drive has a digital-audio out (a 3 or 4 pin connector) isn't that what you want?
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Postby Steve Anderson » Thu Jun 07, 2007 8:25 pm

M3DVQ wrote:the 40 pin connector is IDE, for data... will this contain the original audio data? :?
if the drive has a digital-audio out (a 3 or 4 pin connector) isn't that what you want?


The only way that my drives can output audio is via the EIDE connector to the motherboard which has the needed D-As etc. They work suprising well considering their cost.

The digital audio-out is in a serial format, (not that my drives have it anyway, they're kinda old) it's a headache to de-serialize as with the standards proposed the 16-bit word needs to be processed in a non-standard parallel manner.

I also don't want to use the on-board D-A, I want access to the raw 16-bit parallel data on the EIDE connector. That in itself is not a problem, I'm just having trouble finding how the data stream is organised. The hardware (pin-outs etc.) are not an issue.

What I am trying to to is see if it's possible (there is no reason why not) that external D-As could be DC-coupled and each chunk of the 16-bit data be diverted into either the monochrome channel, or the appropriate colour decoder, or processed in some other way.

It's also conceptually possible to use the lower 8-bits of the right channel for more video data. The right channel D-A would simply ignore these, OK, we end up with 8-bit audio, but as with all TV audio is the Cinderella of the industry, and few care too much about it.

But try watching the news with the sound off!

Steve A.

OK, I'm learning yet again. It seems that the data is organised into 'frames' of 2352 bytes each which represents 1/75th of a second, = 176,400 bytes/sec. Divided by two for two channels, then divided by two for 16-bit audio = the famous 44100Hz sample rate. Someone please check my maths!

This is for audio CDs, it appears that data CD frames are of 2048 bytes each, which would seem sensible.

So my next task is to find out how these frames are composed and what each byte represents.

The interesting thing is that 1/75th of a second is exactly one sixth our frame rate of 1/12.5 sec.
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CD data streams

Postby Viewmaster » Thu Jun 07, 2007 10:52 pm

I searched on 'groups' on Google.....
On this group they mention data streams for Sony etc.

http://groups.google.co.uk/group/sci.el ... 5c66c57343

The link to the data stream protocol from this group thread is here.
Might be closer to what you are looking for?.
Scroll down for data stream clocking etc

http://web.mit.edu/bunnie/www/proj/cdhack/cdhack.html

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Postby Klaas Robers » Fri Jun 08, 2007 1:34 am

I fear that when you connect the CD-ROM drive free, whithout a computer, and you push the play-button, that there is only analogue sound, no digital data on the IDE connector. The IDE data only appears when a command is given by the computer. Then the speed is also not audio real time, but much faster.

An audio HiFi player has a digital out connector, or coax of optical, which gives the audio data in a specialized serial format. Certain IC's can de-serialize it and convert it into parallel data words. In the Newsletter this is explained and shown how to make RGB of it. We (Vic and me) should find time to make the PCB's available for a reasonable prize.
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Postby M3DVQ » Fri Jun 08, 2007 4:42 am

is this the same format as the "digital audio out" connectors on the CD drives then? it's a 3 or 4 pin connector, it would be interesting to see if this output can be used to get the parallel data required.
IIRC the digital audio out is active when the cd is playing audio with the "play" button too. it is one of the ways the signal can be sent to the soundcard for playing out of the computer speakers (the other way is an analogue connection to the soundcard on a similar connector)
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Serial digital stuff.

Postby Steve Anderson » Fri Jun 08, 2007 1:08 pm

Thanks for the data gents, and the links were useful too.

Hmm...it's all more complex that I thought it might be, I was (foolishly) hoping it would be a lot simpler than it is.

What I hadn't noticed before that in fact both of the CD drives do have a serial digital output on the rear. It's just a 2-pin connector, ground and data.

What sort of signal dribbles out of there I don't know, I've never seen it used before. Until yesterday I have never used the analogue output of a CD drive, either on the front or the rear.

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Postby Klaas Robers » Sat Jun 09, 2007 6:54 am

There are several names for the digital audio out stream. One is EBU (European Broadcast Union). It is serial data out in a certain format, of which several are available. Vic uses an IC that converts the serial data in other serial data, but now with separate clock and a Right/Left signal. This is called I²S. This I²S stream is easily parallelised.
Quite some CD-players have such an output, most of the time a cinch coaxial connector, sometimes an optical (plastic) fibre.

I never have seen a CD-ROM player that has this type of output. The 3-pin connector is analogue audio Left, Ground, Right out, which can be connected to the Sound Blaster Card and thus connected to the loudspeakers.
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Postby M3DVQ » Sat Jun 09, 2007 8:18 pm

odd, at least one of my drives definitely has two small connectors. and calls one digital. I shall have to remember to look next time I have the pc open
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CD ROM Drives.

Postby Steve Anderson » Mon Jun 11, 2007 9:14 pm

Here's the back-end of one of the spare CD ROM drives I have, they're both the same. Speaking to my PC Guru here he says they're all the same. This is a PC drive, not a player in the stand-alone 'Hi-Fi' sense.

However, he wasn't able to shed any light on the data that comes out of the 'digital' port, and like me, has found that no-one uses it or the analogue output of the CD drive itself. Perhaps that's why the DVD/CD burner in my desktop (Samsung) doesn't have an analogue output.

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Re: CD ROM Drives.

Postby M3DVQ » Tue Jun 12, 2007 1:12 am

Steve Anderson wrote:Here's the back-end of one of the spare CD ROM drives I have, they're both the same. Speaking to my PC Guru here he says they're all the same. This is a PC drive, not a player in the stand-alone 'Hi-Fi' sense.

However, he wasn't able to shed any light on the data that comes out of the 'digital' port, and like me, has found that no-one uses it or the analogue output of the CD drive itself. Perhaps that's why the DVD/CD burner in my desktop (Samsung) doesn't have an analogue output.

Steve A.


I use the analogue port on all my CD drives, otherwise some software has no sound, if it uses CD audio (same if you want to listen to music cds, although I think modern OSs can get the audio off digitally hence not requiring the cable any more)
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Re: CD ROM Drives.

Postby Steve Anderson » Tue Jun 12, 2007 12:31 pm

M3DVQ wrote:I think modern OSs can get the audio off digitally hence not requiring the cable any more)


I build my own PCs (not laptops of course) so I get it exactly the way I want it. I buy the case and PSU from one place, the motherboard, processor and RAM from another, drives from yet another...and so on. I have never had to use those connectors on the back of the drive and the PCs do all that I wish, play music, VCDs, DVDs no problem.

I think that's why the most recent drive I bought doesn't have an analogue output, even on the front, no-one seems to use it, at least around here.

There is also the consideration that if the drive is a burner/writer then it's logical that it should have an analogue input. But they don't....keeps the cost down plus managing it could be a bit tricky.

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