Laserdisc PCM Capture Guide

[Falcon]

On Audacity the capture works (except that we don't get the famous bitperfect on audacity)

16 bit audio can be captured without alteration of the audio in Audacity as well. The trick here is to select either 24 bit or 32 bit floating point during the recording session and save the result to 16 bit to avoid the dithering. Otherwise, the least significant bit will be altered, corrupting any AC3 or DTS data.

Also, I'd suggest using WASAPI as the interface.

Ok, thanks ! 
The Bit-Perfect testkit works with audacity in Wasapi mode / 24 bit capture / 16 bit export ? 
If i deasactivate dither, can I capture in 16 bit ?

I can't use the testkit, because my LD player can't read audio CD (no audio CD works and I don't have DTS LD)

[zoidberg]

A CD/DVD player with optical out should be able to play the DTS CD (as long as it's set to bitstream).
If your capture device can handle the test CD then you should be all set, pretty much all LD players are bit-perfect by default

[little-endian]

The Bit-Perfect testkit works with audacity in Wasapi mode / 24 bit capture / 16 bit export ?

Yes.

If i deasactivate dither, can I capture in 16 bit ?

No, at least not for me as the assumed dithering seems to already happen in the driver, so also in e.g. Goldwave, I have to select 24 bit in the recording device settings when using DirectSound as the interface (as WASAPI support apparently is buggy for me with random recording stops). Anyway, before exporting the recording to 16 bit, the only minor drawback here is a 50% higher temporary storage usage.

I can't use the testkit, because my LD player can't read audio CD (no audio CD works and I don't have DTS LD)

That is tricky as if you only can playback LaserDiscs, you'd have to record something which has already been done so by others and compare that result.

Neat alternative of course would be to bravely go on eBay and get at least the "mother of DTS" and cult "Jurassic Park" on LaserDisc. Compared to some other titles, that one isn't even that expensive and belongs to any halfway decent collection, I'd say.

[Falcon]

Thank you all for your help.
I tried to capture DTS from DVD (capture in 48Khz), I can't decode it with DTS Parser. I guess the reason is either:
-DTS Parser is made for DTS 44.1 kHz
-I started the capture while the DTS was launched, and cut the capture before the end (first and last DTS frame could not be "finalized") and DTS parser fails to delete the unnecessary samples.
I can't get Wav2dts to work unfortunately ...

By cons I compared captures with my friend with a LD that we had in common (highlander), I tested with this:

-Windows 7 (CSL USB 7.1) Audacity (Wasapi / capture 32 bits float / export 16 bits)
-Windows 7 (CSL USB 7.1) Reaper (Asio / export 16 bits)
-Macbook Pro (mini toslink) Audio Recorder capture 16 bits
-Macbook Pro (mini toslink) Audio Recorder capture 24 bits
-Macbook Pro (mini toslink) Quicktime capture 16 bits
-Macbook Pro (mini toslink) Quicktime capture 24 bits

The 24 bits WAV files, I converted them to a flac with EAC3to, this one showed me "The original audio track has a constant bit depth of 16 bits." and it reduced the tracks to 16 bits automatically.

-I aligned the samples on Adobe Audition
-I compared each captures with DeltaWave

The result was 100% identical each time.

So I can consider that my setting allows me a perfect capture

[bendermac]

@Falcon

Just rip the DVD. No need to capture anything and trying to get it to work

[Falcon]

The objective was not to recover the DTS from the DVD, but to test my captures...

[bendermac]

AFAIK, This will not work.

You need a DTS CD

[Falcon]

The DTS CD is to test the player, if you don't have a DTS laserdisc.
You can capture AC3 or DTS in the same way.
I already tried to capture AC3 and DTS in this way. Mediainfo immediately recognized my DTS 1509 in my Wav, and my AC3 640 in another wav.
The problem now is to decode them.
My goal is to be able to capture AC3 from the TV box or VOD platforms that broadcast in AC3.

[DeafYakuza]

What about the sound card of Blazer Sound Z that I have and it supports ASIO input and output?

[pipefan413]

This is the first time I've tried recording using Reaper. My previous LD PCM rips were done using WaveStudio, it isn't as configurable and is meant to just do what the sound card tells it to do. I didn't see the same problem using WaveStudio but I've also not been able to pass your DTS CD test using that so wanted to try something more accurate.

I'm away from my computer just now, but when I get back I'll try recording from a laserdisc into Reaper to see if I can hear any kind of skipping or speedup, for some reason I didn't think of that earlier.

I'm using ASIO4ALL because Creative's ASIO driver sadly has a problem with this card at 44.1 kHz. I'll experiment with different protocols too. Any you recommend?

Thanks for the help.

I'm currently fighting with another Creative Sound Blaster card: the ZxR + DBPro. It would appear that it too is a bit iffy.

I initially tried it with the built in ASIO driver, which defaulted to 48 kHz, so I set Reaper to "request" 44.1 kHz" to see if it worked. It did, but it wasn't bit-perfect, so I figured there was resampling going on. So then I tried ASIO4ALL instead, which reported that the WDM driver could indeed capture anything from 32 to 96 kHz through the digital input on the DBPro, yet it still isn't bit-perfect even when the driver is ostensibly passing Reaper 44.1 kHz at 24-bit.

The thing that seems to be consistent through every test recording I've done though is that DTS Parser doesn't render anything. The output file is completely empty, 0 bytes.

Is there something really dumb I might be missing that could cause that? For instance, does it matter that there's silence at the start of the Reaper .wav file (i.e. after I hit record and before the player actually starts playing the CD)? Don't know if I should be deleting it in Reaper before putting it through DTS Parser or what.

I thought I had posted this before, but there's a tool that will replace the process of using dtsparser and then xvi32 to fix the frame headers. It's called "Wav2dts". It was developed by tebasuna over at doom9, and altered a bit by me to make it more usable with LaserDisc captures.

It can basically be used as a drag and drop interface on windows. Drag the Wav file you've recorded onto the .exe, and it will strip any padding from the beginning and end, convert to 16bit standard dts format, and correct all of the frame headers, in one step.



Here's the compiled version and source code:

https://mega.nz/#!DZUXTKRa!VJIvzhMSa4Fit...ecUZT4cOaU

Tried this in case the problem I described above was something to do with DTS Parser on my system, but I can't get the wav2dts.exe to run at all because it throws up an error saying it can't find "libgcc_s_dw2-1.dll":



Anybody have any ideas?