Sound with the Computer

There are two manners to use the computer as a source :

The most common manner is to use the computer as a digital source and to use an external DAC (most of the time an AV Amp). You just need a good sound card that supports 44.1 Khz without resampling. Most of the cheap cards only support 48 Khz and so they resample every 44.1 Khz signal to 48 Khz. Having a 44.1 Khz compatible sound card allows not to spoil CD-Audio LPCM, it just pass it through the card without resampling. You can also read DTS CD-Audio that use 44.1Khz. An AV amp receiving resampled DTS will play a kind of rose noise. When you got a decent sound card, you just need to use Foobar with Kernel Streaming (Foobar2000 > Preferences > Output > Kernel Streaming), chose your soundcard in "Go to Settings".

To play DVD's just choose the digital output in the player settings.

Actually this is not that kind of use I am interested in.

My PC replaces CD player, DVD player, preamp and filters, this is more complicated but much more interesting. Of course, as the sound card is doing more job, it needs to be a good quality sound card. We are not talking of consumer sound cards here even the best Creative sound cards. The choice of the card depends on what you want to do and in particular filtering/Room treatment or not. If you don't want to process sound you can choose any pro sound card you want otherwise stick to Esi.

Decoding sounds

1° Decoding stereo sound files :

Just use Foobar with the Kernel Streaming output (or Asio, plugin needed). Using a power amp directly on the sound card, volume is set in the sound car panel. As the sound card DACs are working at least in 24 bits, you can reduce sound volume a lot before having digital loss. If the sound volume tou want is too low (-X db), its digital code will encroach the code of the sound and there will be quality loss.

Decoding sound from DVDs

What you need is Zoom Player Pro : you can choose the video codec you want, the audio codec you want, audio and video render. Among all the codecs available : Cyberlink PowerDVD, Intervideo WinDVD and AC3Filter. Zoom Player Pro, DVD mode, Player Options :

As we are decoding sound with the computer, the choice of the codec and its settings are very important. the most important thing is to remove dynamics compression and to avoid clipping (AC3 filter for example plays too loud). I chose AC3 filter for the moment because it offers a lot of options.

ZoomPlayer, filter properties, AC3Filter :

Remove Auto Gain and Auto Matrix as they bring dynamics compression. Remove DRC in the Main. You your own matrix coefficients, if you use 5.1 just put 1 on the diagonal, if you use 4.1, 1 on the diagonal exept for the 2nd column (0.7071, 0, 0.7071, 0, 0) : this will send the central speaker to the front speakers.

ZoomPlayer allows to use Reclock as an audio render. It allows to synchronize video and sound based on the video card clock. It also allows to correct the "Pal Speed-up" problem : movies for the Cinema are recorded using 24 frames per secondes. When put to DVD using 25 frames par seconds, if the change of speed is not taken in consideration, there is a kind of shift to the high frequencies, a little bit as the doppler effect. Some DVDs are corrected others not. You can find lists on the internet. You can easily notice if the DVD has a corrected sound or not : natural of the voices and soundtracks allow to judge.

If Audio speed was already changed, put reclock on 25 fps. On 24 fps it will be too slow.

If Aduio speed was not changed, put reclock on 24 fps. On 25 fps it will be too fast.

It is better using a video refresh rate that is a multiple of the chosen speed.

Filtering and effects.

Why doing active filtering :

Settings are quite easy and overall instantaneous (which is not that easy if you use passive filters). There is no loss between amps and speakers, no interaction between the speakers. The speakers are not "slowed down" by the components of the filter. You can use a specifi amp for each way, in particular a very powerfull amp for the low frequencies.

Why digital filtering on a PC :

Everything is done before any Digital-Analog conversion. You can use FIR filters, professional quality tools and plugins.

Filtering on stero sounds with any decent card :

You can use a foobar plugin that allows to do filtering. http://sourceforge.net/projects/xover/ You can choose the cutoff frequencie, type of filtering, gain, ...

Another great software is ACXO, working in Asio mode : http://pcazeles.perso.cegetel.net/acxo.htm

Now to do better and overall with any software (so this will include DVDs), you need a card that can do internal routing, such as ESi or Audiotraks with the great Directwire tool !

Directwire allows to redirect digital audio sound from one application to another. We are going to redirect WDM sounds from software like Foobar, Zoom Player, BsPlayer to an Asio application that allows to load any VST plugin. Now the possibilites are HUGE, you can use any professional plugin you want, this will include Voxengo Pristine Space to do convolution !

Esi Waveterminal 192X control panel :

Directwire of the Waveterminal 192X :

Now what we need is a software that allows to load VST plugins, There is Nuendo Surround Edition which is great. There is also NSP (Native Sound Processor) that loads VST plugins with few CPU load.

Here is NSP :

Setup > Routing allows to setup the IO routing. As we are going to use Stero plugins, we setup the IO in pairs. I am using bi-amping but the procedure is the same if you want more ways :

Then we can load the plugin we are going to use for filtering : Izotope Ozone 3. Load one plugin for each way of the crossover. Two for me.

Now we are going to setup the first plugin for a high pass filtering for the mid and high frequencies :

Activate parametric equalizer. Use digital mode. Show info, keep node1 using Highpass, put the cutoff frequencie and a high slope : 12 (about 96db/oct).

Let's do the same thing for the second plugin using low pass on node5

Play sound in the software you want and push play on NSP :

The filter is working well, the first four outputs are used :

Here is a page about VST plugin and all in french by my friend Lansing.