[vdr] Re: 5.1 Sound with analog soundcard?

[Marcel Wiesweg <marcel.wiesweg@gmx.de>]

Am Donnerstag, 3. Juli 2003 09:45 schrieb Markus Schorer:
> hi,
>
> to get a bit more ontopic:
>
> Guido Fiala wrote:
> > Can you give an commandline example where i can feed a52dec with _any_
> > stereo-pcm/mp3-data and it makes 5.1 sound? So far i understand this
> > program can only play ac3-frames just like ac3dec, if your mpeg-stream
> > does'nt have it you hear nothing - unfortunately except Pro7 actually
> > nobody has the money to send such streams - or maybe they are reluctant
> > to buy a licence themselfes ?-)
>
> i do not think the task was to convert any sound to 5.1.
> if i did get it right, the task was to integrate 5.1 and standard stereo
> in a system where you would get both possibilities.

That's it. After all, it is a52dec and not "a52enc".

> in my setup i connect the dvb-s out to the line-in of my soundcard and
> with marcel's plugin we would get the best hearing experience possible.

In my setup, I actually use my TV's speakers for normal output, I use the 5.1 
speakers only for Pro7 and MP3 via a customized MP3OSS plugin.
But that shouldn't be much of a difference.

I have a Celeron 1200, there is a slight delay, I cannot say which audio is 
early, anyway it is almost unnoticeable.
Is 5.1 sound late with your setup? That would be bad.

As I said, I will not "officially support" anything, I will not dig into any 
syncing code, I will only put the plugin on the web.
There is a patch to VDR to mute the DVB hardware when 5.1 data is available.
The a52dec command is hardcoded (using -oss6), aumix is invoked to adjust the 
OSS mixer.
It's a small hack, not worth too many words:
http://www.wiesweg-online.de/linux/vdr/vdr-a52dec-0.1.tgz


> - i think it should be integrated in the audio-track/language switch
For me switching works out of some magic in VDR.
> - do you think we would need a per channel delay or do you think the
>delay
There is only Pro7?
>  depends mostly on cpu power ?
don't know...


>
> i'm not going to say anything on legal/patent issues.

The plugin only executes another program, so if there are issues, they should 
be with a52dec/liba52 (which is integrated into mplayer, by the way).

Marcel



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