How to capture AC3 from Laserdisc on your PC???

[Dave Joerg]

Hi there,

I want to transfer my STAR WARS EP. 4-6 - which I have on Laserdisc with ac3 sound - on DVD. Picture is not a problem but sound. My LD-Player has a modified digital coax output, so there is real ac3 bitstream coming out, not a RF modulated signal. So if I want to capture this full ac3 signal from Laserdisc for further multiplexing on DVD: what do I have to do? I tried to plug the coax into my SPDIF coax input of my CREATIVE AUDIGY soundcard. There is definitely a signal coming in BUT: How do I capture the signal? Is there a program that helps me capturing it to real ac3 Dolby Digital? Recording it as a DD wav didnt work since all my sound editing tools (like Cool Edit etc.) try to treat the incoming signals as "music". I have the same problem when trying to capture a DTS PCM signal from DTS LASERDISCS.

Can anyone help me?

Appreciate your input

Dave Joerg,
Wiesbaden, Germany

[lordsmurf]

No. Not without a special audio input card.

[Perro Grande]

Hi Dave,

If the output is an RF Modulated AC-3 signal, which was common for later laserdisc players (or as an add-on for earlier ones), you cannot record it directly. The AC3 on a laser disk is actually tucked in with the Right ANALOG signal, not the optical or coaxial digital outputs. It is also not native SPDIF -- it is modulated. It would need to be demodulated into a TOSLink or SPDIF signal first. There are plenty of gadgets out there, including on e-bay, to do this. This is why you can mod even the oldest analog only players to handle AC3. DTS, on the other hand, is actually on the digital audio tracks.


If your sound card has an SPDIF or TOSLink *input* then, theoretically, you should be able to record it... I know higher-end cards like some of the M-Audio cards have these inputs. I think some of the audigy cards have a TOSLink OUT, but I don't know about input...

Unfortunately, once you get it converted to TOSLink or SPDIF AC-3, I don't know what to tell you. Then it essentially becomes the same question as the one I asked a few days ago. I suspect that the signal could be recorded with something like cool edit, but I don't know if saving it as a WAV and then using BeSplit to convert it to AC3 (fool it into thinking it is a DDWAV format) will work...

I'm working on this theory, and will let you know if I find anything...

[Dave Joerg]

Hi,

well this is exactly what I tried. I recorded the SPDIF signal of the ac3 bistream of the laserdisc into my high end Audigy soundcard but the resulting wav won't be recognized as a DDwav. I used cool edit to capture the signal. The soundcard does get the signal but it does not remain a clean ac3 when recording it as a wav.
So, this remains to be the problem.

Any more ideas?

Dave

[FulciLives]

I remember reading that Philips is working on a stand alone DVD recorder that can record 5.1 AC-3 although I'm not sure what kind of input it will include for doing that.

Last I heard this model should be out sometime in 2004

It might just be a hell of a lot easier to wait for that.

- John "FulciLives" Coleman

[Perro Grande]

FulciLives,

Oh -- I agree, it would be much easier to wait

However, understanding AC3 and DTS at the bit level and the file level has now become a quest for me... Now I just HAVE to know how and why it works...

[hand]

The AC-3 signal from the laaserdisc player can be demodulated to the modern Dolby Digital format (digital coax or digital optical) using an outboard AC-3 RF demodulator. For example the Pioneer RFD-1. Check eBay. Or there are do it yourself modifications. Other sources of info I found below.

http://www.thadlabs.com/LD_info/ac-3_demods.txt
http://www.planet-dvd.ch/rfd.htm
http://www.laaudiofile.com/ac3mod.html
http://htmg.videogon.com/cgi-bin/buy_cl.pl?accsmisc&1100261162
http://home.q03.itscom.net/nsa/PioneerRFD-1.htm
http://www.soundlabsgroup.com.au/bde/bde_rf_demodulator.htm

[jnk76]

I remember reading that Philips is working on a stand alone DVD recorder that can record 5.1 AC-3 although I'm not sure what kind of input it will include for doing that.

Last I heard this model should be out sometime in 2004

It might just be a hell of a lot easier to wait for that.

- John "FulciLives" Coleman

Right off there website.......not sure where available but it better come to Canada! This thing sounds awesome! Hope it works as good!

http://www.consumer.philips.com/consumer/catalog/catalog.jsp?fhquery=fh_secondid%3Ddvd...SHQVHKFSEKI5P#