[linux-dvb] Antwort: Re: Howto: how to play back vdr recodings with AC3sound.

[Stefan.Hagendorn@lindy.cc]

Thats right. The Stream is just sent to the spdif port .. in theory it 
should be possibe to build a small hardware (without real sound abilities) 
which just outputs the data to the receiver. We don't need the decoding 
part of ac3dec . we just use it's paththrough abilities.

And yes there are Soundcards with 6ch output like the Soundblaster XXX 5.1 
Cards or the newer Version of the C-Media 8738 which also got 6ch output. 
I don't know and I don't belive that this cards have a dolby digital 
decoder on board. The decoding will happen in the software me thinks ....

Stefan




Matthias Weingart <matthias@pentax.boerde.de>
Gesendet von: linux-dvb-bounce@linuxtv.org
09.08.2001 20:58

 
        An:     Carsten Koch <Carsten.Koch@icem.de>
        Kopie:  dvb <linux-dvb@linuxtv.org>
        Thema:  [linux-dvb] Re: Howto: how to play back vdr recodings with AC3 sound.


On Wed, Aug 08, 2001 at 09:59:37PM +0200, Carsten Koch wrote:
> Step 1: Get a sound card that has an SPDIF output.

> Step 2: Install the latest beta ALSA drivers, library and utilities.

> Step 3: Activate the driver module.

> Step 4: Connect the SPDIF output of the DVB card to 
>         the SPDIF input of the sound card.

> Step 5: Set up the ALSA mixing parameters.

> Step 6: Install the specially patched ac3dec tool.

> Step 7: Run vdr with the "-a 'ac3dec -C'" parameter.

To summarize (for AC3 newbies :-) You transfer the AC3 stream from the vdr
to the SPDIF output of the soundcard, all still digital, all still the 
same
stream (no decoding). To hear anything you need a external decoder and
amplifier. 
 With that I really do not understand why Dolby is fighting against BSD. 
Or
can the driver decode the AC3 and feed the 5+1 audiochannels to analog
outputs (e.g. some soundcards) too?

Are there soundcards available that have the 6 analog outputs on board? 
(No
external decoder required). I guess, external amplifier or active speaker
still required.

        Matthias


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