Capturing Process

AV Capture Cards

There are a few differences between the cxadc and DdD which either @happycube or @simon_dd86 could go into the details if needed. but the main differences.

Sampling speed cxadx runs at 28msps or 35msps depending upon settings with a bit depth of 8. DdD runs at 40msps with a bit depth of 10. The main thing here is that to 40msps is fast enough to capture all of the frequencies required for laserdisc including some of the harmonics that need to be filtered out as with the 35msps there were some high frequency noise introduced due to signal reflections. The second part is the adjustable gain and the 10 bit depth. This gives you 4 times the resolution of cxadc and is needed for CAV laserdiscs where the amplitude of the signal changes across the disc from low levels at the start of the disc and high levels at the end. This causes an issue of the cxadc ether not being sensitive enough at the start or clipping at the end of a CAV side.

As the signal is Frequency modulated you need to sample at high enough speed and bit depth to determine the shape of the wave even if there is a high or low level signal.

The other major factor is that the cxadc has all of the filter circuit before the ADC designed for Video and not RF. The DdD went through many revisions to understand the signals involved and reflections caused. With this in mind the DdD has a custom designed RF front end filter.

In short... cxadc is cheap and good for playing with the system and tools and also fast enough for VHS but may not be ideal due to the filters.

The DdD was designed and built to solve the problems and issues identified by using the cxadc

Domesday Duplicator

The Domesday Duplicator captures the raw RF signal from a laserdisc player’s laser. The player provides the mechanical tracking, focus and movement of the laser over the disc’s surface and the duplicator records the signal. This effectively turns the laserdisc player into a highly accurate optical scanner. The resulting sample is the spiral of analogue data represented by the continuous track on the disc. The aim is to ensure that the sample resolution is higher than the resolution by which the disc was originally recorded. This way you could (in theory) produce another disc from the copy – and that ‘round-trip’ preservation loop means you capture everything on the disc, even if you can’t decode it yet (or if there is data you didn’t know about).

Since the resulting sample is still a laserdisc, you need a laserdisc player to play it. Therefore, the next stage of development is to produce an emulated laserdisc player in software that will play the ‘disc’ and output the resulting sound, video and data (data being a complex mix of Acorn VFS partitions, frame data, VBI, teletext, etc.). Of course, the better the emulator, the better the resulting video and sound – and it’s fairly easy to see how a fully digital emulated player could out-perform a 30 year old analogue VP415 (and the ‘samples’ won’t wear out or degrade like physical discs).

The Domesday Duplicator project is completely open-source and open-hardware. [...] The hardware/software solution was originally designed to act as a sampling front-end to the ld-decode (software decode of laserdiscs) project and replaces the generic TV capture card to provide high-frequency sampling with 4 times the sample resolution. Increasing the sample resolution allows better capture of disc overall however, the primary advantage is that the Domesday Duplicator provides better performance for weaker RF signals especially at the start of a laserdisc (where the RF output has lower amplitude) and when the disc is degraded due to age and surface damage.

Digital Audio Capture

For recording the digital audio tracks on a LaserDisc, (uncompressed PCM stereo, Dolby Stereo, DTS, or demodulated AC-3), you'll need an audio interface with either TOSLINK or Coaxial S/PDIF inputs. For AC-3, you'll have to first connect your LD Player's AC-3 RF output to an AC-3 RF demodulator, and then send this demodulated signal to your audio interface over TOSLINK or Coaxial.

Your audio interface also needs to be capable of "bit-accurate", "bit-matched", or "bit-perfect" recording. Some interfaces will resample digital inputs to a different rate. If you are recording PCM stereo this may not be an issue, but if the interface performs any resampling of an encoded track like DTS or demodulated AC-3 it will be ruined. Look for devices that support ASIO. A device which states it does not support S/PDIF surround passthrough is not necessarily bad for recording encoded audio, but it definitely won't allow you to send a surround signal directly to the S/PDIF output for real-time listening. For PCM stereo, record in 44.1KHz/16-bit.

For encoded formats like DTS and AC-3, the recorded signal will sound like noise if played back directly. You'll need to use software which can decode your file and save it to the appropriate format such as .ac3. For AC-3, make sure to record in 48KHz/16-bit.

Hardware

Only bolded items are confirmed as working for digital audio recording of encoded formats.

PCI/e Sound Cards

(Pre-Windows 10)

• ESI/Audiotrak Prodigy 7.1 HiFi
• M-Audio Audiophile 2496
• M-Audio Audiophile 192
• M-Audio 1010LT
• M-Audio Delta 66
• HT Omega Striker 7.1
• HT Omega Claro (Plus)
• HT Omega Claro Halo (XT)
• Creative Labs Audigy (Emu10K-2 chip w/ custom KX driver)
• Creative Labs Audigy 2 (Emu10K-2 chip w/ custom KX driver)
• Creative Labs Audigy 2 ZS Series
• Creative Labs Audigy LS
• Diamond Xtreme XS71DDL
• Terratec Aureon 5.1

(Windows 10 Support)

• Creative X-Fi series (w/ Front Panel Hub)
• CMI878x, CM88xx
  • Sedna SE-PCIE-SC-10 7.1 Channel Sound Card (CM8828 + CM9882A) w/ S/PDIF Bracket
  • StarTech.com PEXSOUND7CH 7.1 Channel Sound Card
  • HT Omega Fenix (w/ CA-1 Coaxial Digital Input Cable)

USB External Sound Cards

(Pre-Windows 10)

• ESI Waveterminal U24
• ESI Waveterminal U2A
• M-Audio Audiophile USB
• Sabrent USB-SND8 Sound Card
• Serounder USB 7.1CH 3D External Sound Pocket
• Optimal Shop USB 2.0 External Sound Card 6 Channel
• Terratec Aureon 7.1 USB
• Phonic Digitrack

(Windows 10 Support)

• ESI U24 XL
• Creative Sound Blaster X-Fi HD USB Audio System
• A ADWITS 7.1 External USB Sound Card
• V.TOP 7.1 USB Audio Adapter
• StarTech.com ICUSBAUDIO7D 7.1 USB Sound Card
• Vantec NBA-200U USB External 7.1 Channel Audio Adapter
• HISU 6 Channel External Sound Card
• Ebetter USB 2.0 External Sound Card
• Hauppauge HD PVR 2 model 1512

Other

• 2011 Mac Mini

Software

Recording

• Cool Edit
• Sound Forge
• Cockos Reaper
• Creative WaveStudio
• Apple Logic X

Decoding

• BeSplit
• DTSparser