[vdr] Re: Direct AC-3 yes or no ?

["Dr. Werner Fink" <werner@suse.de>]

On Wed, Jul 16, 2003 at 04:27:15PM +0200, peter.zeipelt@arcor.de wrote:
> Hi ML 
> 
> Again a question to the well discussed topic AC-3 through the S/P-DIF on the DVB-S. 
> My aim is to setup a full featured VDR-PC, with mp3-, divx-support and so on. 
> After reading a lot of postings, I think it's actually not possible to bring
> the "live" (I mean while I'm watching the actual TV-Broadcast and no recording)
> AC-3 from the DVB-S to the external amplifier without a loop through an alsa-supported soundcard. 
> And I don't know, if the mp3-plugin has the ability to bring the sound to the S/P-DIF of the DVB-S. 
> The only program I found supporting this feature, was mplayer. 
> I know that it's possible to watch recordings with AC-3 using a soundcard and that
> the mp3-and even mplayer can use the soundcard, too. But with mplayer using the
> soundcard as outputdevice, I have nearly 100% CPU-Load. Using the DVB-S as output I have only up to 60%. 
> I can solve the problem with to cables fro the PC to the amplifier. But in fact, I want
> to eliminate the soundcard and save connectors at the amplifier for other devices. 
> Can someone tell me exactly that I'm right, or is their a solution to eliminate the soundcard? 

Hmmm ... the only real way would be support of embbeding AC3 into
PCM in the _firmeware_ of the DVB card.  The only problem is (AFAIK)
that the PCM stream can not be marked as none audio stream.
This leads to the problem for lazy A/V receivers which do not
look into the PCM stream to detect the AC3 data therein but
put the PCM stream directly to the D/A decoder  ... that isn't
realy funny for your ears and the boxes.

Nevertheless, for all other A/V receivers it would be an
perfekt option.  No transport over the PCI bus, no synch
problems between live AC3 data streams and the quart onto
the sound card.

_BUT_ that the firmware is closed source, in other words: without
support from convergence and signing a NDA I see no way to
extend the firmware.  On the other side I guess that the source
its self is written in C ...


         Werner


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