CED VideoDisc and Player Discussion

[TGM]

I was randomly wondering if anyone knows or has ever posted the structure of the DAXI codes and what all the bytes in the DAXI do and how to possibly replicate them. And also, how much raw data can a videodisc actually store, how much video data is between the DAXI codes, etc. I guess just information about the DAXI data itself and the actual type of video data in general.

I’m wondering because I’m thinking of something like an ODE (Optical Disc Emulator) device like for the PS1 and GameCube, but made for CEDs. Using something simple like a raspberry pi, could there be a possibility to emulate a video disc on real hardware? It could also allow re-encoding any video into a CED format. It might be a way to keep a similar video disc experience even after all the styli are used up. Idk if I’m smart enough to do it, but with enough info, maybe I or someone else could.

Does anyone know how the DAXI and the actual video format works so one day this idea could have a chance to become a reality?
_________________
Glitchy Mario

SJT-100 (not working )
Sears 934.54780150/CED-1 Frankenstein

[emceebois]

The first step for making a CED ODE would be figuring out optimal settings to capture raw contents from the disks using something like a Domesday duplicator. I think more useful than an ODE, though, would be either a software decoder for the captures (equivalent to ld-decode or vhs-decode) and/or a new kind of player that uses lasers instead of styli to make it so playing back original disks didn't introduce new wear. I think the former is probably significantly more realistic than the latter.

That's just high-level overview knowing what goes into preserving analogue media formats, though. Actually making "ced-decode" software would probably depend on reverse engineering any format-specific quirks used when encoding them. What are you referring to when you say DAXI codes? Is that at all related to the banding used on random access disks?

[ketonic_dude]

I know a couple people who may be able to explain it to you. The first guy I know actually contacted me out of the blue one day and said he was hired to preserve a CED in the finest quality possible. He was in the process of restoring a SFT100 to it's absolute factory specifications that produce the finest picture. He had a monitor set up that would show the daxi code even. It was pretty crazy. His name was Maurice Schechter and he was out in New York if I recall right. Here is his email if you would like to talk to him, mauricsch@cs.com. Here is the final copy he made if you care to see just how good a CED can look, careful, it's a big file.

https://drive.google.com/file/d/1zgDF91FU6EqCmKfiTAtakZZLOWm1oC3x/view

The 2nd guy I know actually worked with the daxi code. His name is Ted Dudziak and he is on the CED Magic Facebook group. He said, "I moved on to designing the DAXI generators that were conceived and designed in Princeton, NJ labs by a very smart engineer named Charlie Dietrech. The designs were not quite right for Mastering so I was asked to make them more compatible. As a result I was referred to as Mr. DAXI by the Mastering group at Rockville Road. I have the released versions of my schematics of the design which was given to me by them when I left." and then he made a post that said...

"OK so you want to know how the DAXI code works. Below is a writeup for the DAXI chip that is in the player. But first some words about how the code is recovered from the video signal. The DAXI code is inserted into the vertical interval of each video field and “looks” like a line of video. The video is fed to the chip and the chip will respond just to the Barker Code at the beginning of the line of video. It will ignore all other lines of video because in the chip is a correlator which is “looking” for the Barker Code which is 13 bits long. The Barker Code has a very unique quality that allows it to exist with all the other content having a VERY high correlation factor so that only it will be detected by the circuitry and not any part of the other video content. The BARKER CODE provides a start signal to the circuitry to start the capture of the information about the VideoDisc content which is described below. The use of autocorrelation codes is very common now and is used in GPS, 3G, 4G and 5G systems as well as WIFI systems. The original DAXI circuitry was invented and designed by Charlie Dietrich at Princeton Labs.
Enjoy!
DIGITAL AUXILIARIY INFORMATION CODE
(DAXI) BUFFER IC
•
Genera1 Description
The Digital Auxiliary Information (DAXI) Code integrated circuit is used in a VideoDisc player to recognize, check and store data encoded on lines 17 and 280 in the vertical interval of a video waveforn. The data is then made available to the player control system via a serial output from the IC.
Pin List
l. Processed Video In 8. Bits In
2. Test Point (make no external 9. CRC Feedback Out
connection) 10. External Clock In
3. 1.53 MHz In 11. Control In
4. Status Out 12. Shift Register Clock Out
5. Data Out 13. Bits Out
6. 1.53MHz Out
7. Ground (O Volts) 14. vdd {+5 Volts)
DAXI Operation
This integrated circuit converts a processed video waveform containing digital information in the vertical interval to a digital bit stream in the bit detector and performs the following sequence of operations:
a. On receipt of a logic “1” on the control line from the VideoDisc
Player Control System, the IC begins shifting bits from the Bits
In input to the two registers in synchronism with the 1.53 MHz
input. In this mode, the CRCEN (Cyclic-Redundancy Check Enable)
line to the 13 Bit Error Check Register is a logic “0” so this
register functions as a simple shift register with the Start
Code Detector watching for the Start Code (see Fig. 2) to appear.
b. When the Start Code is recognized by the Start Code Detector,
the Controller sets the internal CRCEN line to a logic ”1”
converting the 13 Bit Error Check Register to a cyclic redundancy
checker. The controller simultaneously enables a counter
which counts the next 64 clock pulses on the SCLOCK line to the
shift registers. A cyclic redundancy check is performed on the
64 bits shifted into the registers in this mode.
c. At the end of the 64th shift, the Controller disconnects the
SCLOCK line from the 1.53 MHz clock in a manner which does not cause a clock pulse due to the switching. The last 24 message bits (see Fig. 2) remain in the 24-bit shift Bit Error Check Register. If the data is valid, the register will have the same bit sequence as the Start Code and the Code Detected line will be at a logic “1” • Simultaneously, with the end of the 64th shift, the Controller forces the status line to a logic ”1”
•
d. When the Player Control System recognizes the logic ”1” on the status line, it changes the control line to a logic “0” which causes the Controller to connect the External Clock Line to the
SCLOCK line in a manner which does not cause a clock pulse due
to the switching. The external clock line is at a logic “0” at
this time. The status line then indicates a logic ”1” if and
only if the cyclic redundancy check indicates valid data.
e. The Player Control System reads the status line. The External
Clock Line is then clocked by the Player Control System at a
low frequency rate, shifting bits from the IC's 24-bit Shift Register to the DATA line.
f. The Player Control System then times to the next interval and sets the control line to a logic ”1” to repeat the process
beginning at (a)."

It was followed by two pictures of the daxi chip design and the daxi signal design. I can email you the pictures if you would like them, otherwise here is a link to the post and the pictures are in the comments.

https://www.facebook.com/groups/36668183795/permalink/10159598130338796

[TGM]