linuxaudio.org

Clemens Ladisch wrote:

quoted text
> Florin Andrei wrote:

>> [...]

>> But with the PC, once the digital coaxial carrier comes up, it's always

>> ProLogic and 2.1, never Dolby Digital and 5.1

>

> SPDIF was designed for stereo, so it has only the bandwidth for two

> channels of data at 48 kHz.  (There are extensions for higher sample

> rates by increasing the clock, but there are never more than two

> channels.)

>

> To transport more than two channels over SPDIF, the audio data has to

> be compressed so that it fits into the bandwidth that two uncompressed

> channels would use.  There are two common codecs, Dolby/AC-3 and DTS;

> both are heavily patented.

>

> Any sound card that wants to encode multichannel audio for transport

> over SPDIF has to include an encoder license.  Very few do (the Windows

> drivers for CMI8768+/8770/8788 and some X-Fi cards come with encoders).

> Without encoder, 5.1 playback works only when the source data has

> already been encoded previously (e.g., on a DVD).

Awesome - that clarifies some things I discovered last night when

googling around and doing experiments with the motherboard.
The consensus seems to be it's very hard to do 5.1 over S/PDIF unless

the data is already encoded like that (DVD) - you provided the

explanation for that. So, if I play a DVD it might be doable, but if I

play a game that has capabilities for 5.1 output, most likely it will

not work.
What I discovered is that the sound chip on the mobo can send 5 audio

channels over analog. I guess that should remove all limitations, isn't it?
> AFAIK there is no Linux distribution that ships with an encoder,

quoted text
> but you can download and install an AC-3 encoder manually (see

> ).

Is there anything similar for Windows? Some sort of universal plugin

that works with any card?
--

Florin Andrei
http://florin.myip.org/

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