Decoding of AC3 streams with a 5.1 soundcard and 6 channel analog out

[Mental_CEO]

It is easy to explain how ac3 decoding is done via S/PDIF out: The Player (e.g. PowerDivX NextGen or PowerDVD) sends the AC3 stream unchanged to the soundcard´s S/PDIF out and the external Dolby Decoder decodes it.
How are things done when I use a 5.1 soundcard with 6 channel analog out? Which "tool" plays the role of the external Dolby decoder (guiding the 6 signals of the AC3 stream to the right output of the soundcard; there are 3 outputs to choose), the Player, the codec or the soundcard´s driver. How are these three components corresponding and which does what?

Thank you for your answers

[ookzDVD]

@Mental_CEO,

Welcome to the forum.

If your sound card has the "Dolby Encoder" such as Audigy & Audigy 2,
there is a "special player" from the Creative Labs which will tell
the sound card to decode the stream use hardware decoder.

If you use software player like WinAmp, WinDVD, PowerDVD, the .ac3
will be decode by software decoder (DS filter) and will be output
as your speakers configuration (if your speakers < 5.1) it will be
downmixed.

That's what I know, I hope it will help you.

Thank you.

[valent]

@Mental_CEO.
Here is additional information. There are two choices, if your sound card has AC3 decoding possibility (SB Live! 5.1, Audigy). With any audio configuration, except S/PDIF in the player's settings DirectShow filter (iviaudio.ax, claud.ax, etc.) will decode AC3. If you set S/PDIF in the player's settings, turn "digital out only" off, and set "AC3 decode" in the soundcard's settings, then driver of the soundcard will decode AC3.