Laserdisc PCM Capture Guide

[bronan]

This guide is for doing bit perfect (identical to source) captures of the digital PCM track on Laserdiscs. In general you only need a few things, and the process is very simple. The thing that complicates it is that there is a whole slew of audio interfaces, sound cards, and recording software out there, each with their own quirks and processes. This guide is mainly based on the hardware and software I'm using, but it should still be handy for all since the basic concepts will be the same. So I just want to say up front that I don't think this is the way, just a way. If you use something different or have any suggestions please feel free to leave a reply.

1. Hardware setup



The hardware setup for the capture is pretty straightforward: your Laserdisc player outputs a digital signal via its optical output that is routed into your PC and captured via recording software. The thing that is not so straight forward is making sure nothing happens to the signal between the Laserdisc player and the file that ends up on your drive. There are 2 places where you will commonly get snagged when trying to achieve bit perfect capture: the audio interface and the recording software. Even if a cheap consumer soundcard has a digital input, it's unlikely to support a wide range of sample rates and will just re-sample everything to a certain rate (48 kHz for instance). Because of this, it's absolutely crucial you use a sound card that supports ASIO and can pass through 44.1kHz signals without altering them. In general, pro music recording gear is the best option for both analog and digital capture.

2. Audio Device Config

Once your hardware is all setup and connected, the first thing to do is open the control panel for your audio device and make sure everything is setup correctly for 16-bit digital capture at 44.1 kHz. For instance, on my ESI the input method needs toggled between Digital and Analog, and the Digital input can be toggled between several sampling rates for capture. It's possible your device may automatically capture at the right rate, but I would recommend always installing the driver software and double checking things



3.Recording Software
I tried a ton of different software I saw recommended online for capturing bit perfect, and had no luck with anything except for Cockos Reaper. While it's not free, it does have a full featured 60 day trial that should give you plenty of time to decide if its worth shelling out the 60 bones for. I also use it for syncing (a guide for another day), so for me it was more than worth the price tag. There are just a couple things to do in Reaper before you can begin recording:

- In Preferences, set the Audio System to ASIO:



- Back in the main window, confirm the sample rate on the top right is 44.1 (don't worry about the 24-bit, it won't affect 16-bit captures)
- Create a new track with stereo inputs as shown below. Note that even if the track on the LD is mono you still need to capture it as stereo.
- Arm the track for recording and you are ready to record.



- After recording your track, go to File->Render and copy the following settings:



4. So is it Bit Perfect?

Now that you have a recorded track, you're probably wondering if its really bit perfect or not. Unfortunately there's no easy way for us to compare what we recorded back to what's actually on the Laserdisc, but there is a method where you burn a test CD and play it back in your Laserdisc player. Please see my post on the Bit Perfect Testkit for instructions and more information.

[DeafYakuza]

It sounds interesting and easy to work.

I recorded a sound "Dolby Digital 5.1" (AC-3 Demodulator) from Laserdisc and the format/codec is AC-3. It's the same to do with Pitch Perfect, or?

[deleted user]

It sounds interesting and easy to work.

I recorded a sound "Dolby Digital 5.1" (AC-3 Demodulator) from Laserdisc and the format/codec is AC-3. It's the same to do with Pitch Perfect, or?

Not sure if that's your question, but Dolby Digital is synonymous with AC-3.

[DeafYakuza]

So, I recorded the AC-3 (DD 5.1) 16-bit, 48kHz with Haupauge HD PVR 2 from Laserdisc (LD > RF Demodulator > Haupauge via SPDIF).

What I did with Pit Perfect so that I will get the better AC-3 sound.
I demuxed and distributed all tracks (center, FL, FR, LFE, SL, SR) to a single track (Mono) as wave (16-bit, 44,1kHz) and then I followed the last tutorial (Render to File)(Mono instead of Stereo).
Lastly I muxed it to AC-3 again after Pit Perfect. It's correct so?

[bendermac]

If you're able to capture the AC-3 from a LD then you shouldn't transcode to PCM. If you want to sync it to another source, you can use eac3to or delaycut to edit the AC-3 without the need to transcode.

[DeafYakuza]

Aha... What will be happen if I do transcode to wave and will edit on Vegas for Hybrid Cut and then back to AC-3?

Don't forget that I am deaf and I can't find out the comparison between before and after.

[zoidberg]

Converting a lossy audio format to lossless and then re-encoding back will possibly result in a loss of quality. If you must go this route then it is always preferable to re-encode at a higher bitrate than the original file.

The alternative is to use your transcoded wav files for editing and create an edit log which can be used to edit the original LD AC-3 file losslessly (ie bit-perfect). eac3to and delaycut can both be used for this purpose but you must remember that AC-3 frames are 32ms in length and edits aren't as perfect as you can achieve with wav files.

[bendermac]

I recommend to either edit the AC3 or needed uncompressed, then stay uncompressed

DON'T TRANSCODE TO LOSSY ANY FURTHER!!!

[DeafYakuza]

Thank you for your explains. It means that I have no chance to get lossless quality after editing?
There are no capture cards which can captures 6 channels (AC-3 5.1) to wave directly. AJA LHi or LHe Plus can capture only 2 channels, unfortunately! Only Haupauge is the only one who can do that.
If eac3to can do better can you show me which steps can I do it?

What about Lumagen Radiance XE3D/XE3D+?
Laserdisc AC-3 RCA Output --> RF-Demodulator SPDIF or RCA Output --> Lumagen XE3D/XE3D+ HDMI Out (with correct settings) --> LHi Mini HDMI Input

[bendermac]

If you can capture the AC-3 with your Hauppage, then you most important step already done

In order to edit, using waveforms, transcode the AC-3 to WAV using eac3to

use this command: eac3to (the location it's stored) source (location of your AC-3 file) output.wavs (this will demux the AC-3 into separate channels and to wav)

The you either export your synced 5.1 to uncompressed PCM or you use the info from syncs and edit with eac3to or delaycut