S/P DIF Connections

July 30, 2004

Basically I have recently bought an effect processor. It has a digital out. Is there someway I can plug this into a computer?

What are the possibilities?

Matt Pacini · August 2, 2004

Well, yes & no.

It's not a stock, standard interface that comes with all PC's, so you've got to have something with it, to interface.

For instance, I have an Alesis QS8, which has analog outs, as well as digital.

However, I don't have anything at the moment to take advantage of it, although I will be soon getting a Behringer digital mixer that connects to the PC by USB.

An Alesis ADAT has these ins/outs too.

So unless you have other hardware, it's not going to do you any good, similar to MIDI, for instance.

Matt Pacini

August 3, 2004

I have now found a sound card (creative) capable of recording from it. But is it easy to edit?

I mean, PCM is the standard in audio but I don't think it supports 24bit. I would like to keep the quality. Since DVD has the capability to play at 192khz 24 bit and I have a 24bit processor there?s no point in letting it go to waste.

Actually I wouldn't mind compiling a DVD-Audio disc someday, that would be interesting.

And besides that I would like to record the audio in my next film with the latest in audio to give it that pro finish.

By the way are there any processors out there that run at anything higher than 96 kHz? Mine is 44.1 but it does fine.

Phil Rhodes · August 3, 2004

Hi,

> I mean, PCM is the standard in audio but I don't think it supports 24bit.

"PCM" just means that it's pulse-coded digital audio. Almost all digital audio is PCM, irrespective of the bit rate or depth. "PCM" is also used to indicate an uncompressed computer audio track, but this is a bit of misnomer - MP3 compression is still PCM encoded!

> And besides that I would like to record the audio in my next film with the latest

> in audio to give it that pro finish.

Well - sure, fine. But don't think that it'll instantly get you anywhere - much feature audio is still recorded on 16-bit DAT. It's much, much more to do with microphone placement.

Phil

August 3, 2004

MP3 compression is still PCM encoded!

PCM? Mpeg layer 3 I think, tell me if I'm confusing this with something.

And yeh I agree completely that placement and mixing of the microphones is very important. Much more important than having 24bit audio as opposed to 16. But recording in 24 doesn't take any effort; you should just use the best equipment available. Exactly the same steps but it will come out a bit cleaner.

One thing that always gave me trouble is using one audio track for a set of 5 video clips. I was a production assistant on a film and I was speaking to the cinematographer and he said that you record the audio on the best or first shot taken, and then to get angle changes you still keep that audio track going and mute the others. But, the lip sync wasn't perfect I found.

Alvin Pingol · August 4, 2004

PCM, or Pulse Code Modulation, is defined as "modulation in which a signal is sampled, and the magnitude (with respect to a fixed reference) of each sample is quantized and digitized for transmission over a common transmission medium" (source).

Essentially, what I understand this to mean is exactly what Phil said, is any digital audio. Makes sense if you think about it.

Phil, you said almost all digital audio is PCM... What would be an example of digital audio that was not PCM?

August 4, 2004

Dolby Digital?

Phil Rhodes · August 4, 2004

Hi,

Ages ago, back in the 80s, there were PWM audio systems. The advantage is that if the PWM is at a high enough frequency, it can be used to drive speakers directly. This means you can build very efficient digital FET amplifiers.

Phil

Luke Prendergast · August 4, 2004

PWM amps are becoming more common in professional (as in sound reinforcement) active subs due to the big efficiency increase over traditional linear amps, and the weight savings, and the cheapness. I have to fix the bastards when they break.

At the low end of the spectrum fidelity is not anywhere near so critical, hence the sub part.

Alvin Pingol · August 5, 2004

Thanks, I was not aware of PMW audio systems. I'll have to do some more research on those, as the whole efficiency deal looks quite interesting.

J. Lamar King IMPOSTOR · August 14, 2004

I would like to chime in and say 48khz is the standard sample rate for audio for film/video. I would stick with that as it could prevent possible sample rate compatability issues down the line.

Phil Rhodes · August 14, 2004

Hi,

That's rather a sweeping statement. Other formats, such as 24-bit at 96 or 192KHz, are common, particularly in high-end audio mixing. I would expect to see these systems in use during the final mix of a high-end feature, even if the on-set dialogue was recorded to DAT at 48/16. Even that's less common now, though - DVD-R recording systems are increasingly common and have much higher bandwidth.

On the other hand, your average low budget indie will probably do everything at 48/16. It can sound almost as good, it just doesn't bear as much manipulation (compare the situation with Digibeta and DVCAM.) Most modern computers and home audio gear will happily deal with it and decent results can be achieved.

Phil