I just wanted to say this is very exciting. When I fall asleep tonight I'll be dreaming of ways to scan the pits on a laserdisc. Seriously, this is great and I hope you continue to pursue this. I'll be watching this thread very closely

Best of luck on this. Hope good progress and improvements are made.

Just got analog audio decoding working (no CX, yet, but that can be done as a separate program) and posted the rough code to github.

I'm starting to look at the AC3 encoding - I think i can probably figure out QPSK, but it doesn't look like the patent (edit: on Laserdisc AC3 mastering, not codec) has enough information on how to handle the error correction coding etc needed to get an actual AC3 bitstream. And I don't have a decoder that I can use to get reference data.

The ATSC A53 document has much more complete reference information on AC3 than the patents.

I'm pretty sure I can use libav code to decode the AC3, I just need to figure out how to get the AC3 bitstream out of the QPSK.

EDIT: For now I'm going back to the TBC/NTSC handling, and starting a hopefully better and much more understandable rewrite! Thanks again Disclord for suggesting Isailovic's books - "Videodisc Systems" is very nice.

(I've basically got a couple of weeks to get as far as I can before the local Startup Weekend, where I'm going to pitch something completely different...)

You may or may not already know and be doing this... But laserdisc has TOC (table of contents), frame number, closed captions, and other info stored on un-visible NTSC lines. NTSC has 525 lines all together and I'm hoping that's what you're trying to process.

Here's a quote from MAME author Aaron Giles:

He basically states there's information on the video signal that's visible, provided you capture all 525 lines of resolution. When playing back the video you can do whatever is required with the extra picture (looks like noise but it can be converted to digital binary form); all that's needed is capturing all 525 lines of NTSC reolution. Most of this data is probably more useful for CAV laserdiscs and videogame laserdiscs, but I think it's still worth doing even for the most basic CLV laserdiscs (even if it seems redundant).

Another quote (Aaron Giles):


Here's links with more info in case you haven't already read it and want to understand more of it (hopefully!):
http://aarongiles.com/?m=200807
http://aarongiles.com/?m=200808

Think the biggest problem with Laserdisc players is the composite encoding quality. Quality differs greatly from player to player and colors can be completely wrong; this is probably mostly on 80's to early 90's players. Composite quality on a modern VHS deck (2000 or newer) will jump big time vs an early 90's to 80's model for example, and I think you can get RGB like quality with dscaler or v4lctl with newer composite devices. It's a shame RGB wasn't used in the states like in Europe (marketing over quality takes the lead in the states it seems).

Here's an example of what I mean (composite Laserdisc left; DVD right; courtesy of evildragon)
REMOVED due to bad example
[url][/url]):

A software image decoder for laserdisc could alleviate these hardware problems.

I've already handled the white flag... and I think the Lion King did have blue in it, a lot of Disney DVD's are known to have altered color.

It took me a long time to realize the capture setup I have glitches. I thought it was a player glitch until I realized that each one was exactly 2K long, and pulls in data from earlier. There's some sort of sync issue with the data capture itself... I want to figure out a cheap way to capture the analog data over USB anyway so it's easier to reproduce, but I haven't figured out how yet. Ideally there'd be an affordable USB3 ~100mhz ADC, but there isn't yet.

I'm thinking something involving a Beaglebone Black might get up to 8fsc/28mhz, but I haven't tried anything yet.

In any case, once I have the glitches fixed, I should be capturing and decoding pretty nice video.

(edit 11/29/13: Fixed the capture glitches. Also, while trying to work out on what I thought was dropout compensation, I figured how to correct for some of the pre-emphasis stuff. New captures and hopefully video coming soon(tm) )

Pre-emphasis is a birch. It's very hard to compensate for correctly...

... and almost every LD player fails to do it quite right. Maybe the X0 does. (and possibly the player Laserdiscmodder re-capped etc - at least he claimed/showed it...) Perhaps when new the PR-7820 did as well, but if it used electrolytics they probably drifted by now.

Basically a sharp brightness change is exaggerated/pre-emphasized, and the player needs to de-emphasize it in return. When done properly, this reduces noise since the shifts are reduced. When not done properly, you see ringing once the signal returns to the proper level, and that shift gets de-emphasized as well, even though it shouldn't.

This is why you see ringing/ghosting on test patterns.

Checked in new versions last night (except for the capture glitch itself) - anyone got good examples on how to set up a de-emphasis filter? The one I have now is not quite right, but it does improve SN quite a bit.

You got me thinking about recapping a player now. Shame on you. That's a project I love to hate. Hello digikey.

ok. what the %&^* am i missing here.
what are new caps going to do that old ones don't??
and are you people even watching LDs or just talking about changing out caps for ones that have been sitting on a shelf at some electronic
supply store shelf for 10+ years, or even using OIP caps since they are better or what????????????????

this topic is SOOOOOOOOOOOOOOOOO BORING that i think it's worse than james mariokarts worth the risk
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the rein-o official signature:

It's something to do if you have the spare time. It really can't hurt to change out 25 year old electrolytics.

As for watching LDs I just finished the CAV box set of Alien tonight and thoroughly enjoyed it.

good
i just watched an LD tonight also

someone told me about a saying that someone says, it's PFM
so if it makes you happy change the caps i'll only do it when the player won't turn on.
no other reason to
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the rein-o official signature:

Just posted a test video from an obscure 1981 Pioneer disk, "Rock Adventure" - unfortunately the disk is a bit dirty/rotted, but I wanted to post something that wouldn't set off MPAA lap dogs

http://www.youtube.com/watch?v=FYru56W57jA

Happy to see that your project has reached a so advanced status!

I can't wait to see a state-of-the-art software decoder, and a way to do it using cheap finished hardware...

Vroom vroom!

Wow - looking awesome ! I've unfortunately been very busy in real life the past few months, so haven't made much progress on comb filter decoding, but from the look of things you are almost done !

Thanks I'm uploading a version made with my current code now (I re-did the TBC and put the comb filter in the same program)

My comb filter is good for less sharp footage - it breaks down on something like the Star Wars JSC which is very sharp. It uses heterodyning to get the color information, runs it through a low-pass filter, then adds the out-of-phase bit of that into the combined picture. So it's basically a fancy notch/bypass filter. I don't know when I'll have the time to make a *good* comb filter, but when I recap VE I can send you some unprocessed NTSC output if that'd help you...

LOVE THIS PROJECT!!!

any updates?