[linux-dvb] Re: DVB and dual audio

[Johannes Stezenbach <js@linuxtv.org>]

Robert Schlabbach wrote:
> From: "Gerd Knorr" <kraxel@bytesex.org>
> > Ondrej Zima <amiandrew@volny.cz> writes:
> > > I have problem to select audio channel if the broadcast is in dual
> > > languages. It plays from the left audio channel the native language
> > > and from right the original language.
> >
> > Uh, thats a pretty strange way to broadcast dual-language ...
> 
> No, it's not. This has been provisioned in the MPEG audio standard right
> from the start.
> 
> > Do you know how that differs from mono/stereo broadcast
> > (i.e. how to detect this in the software)?
> 
> Check the "mode" bits in the MPEG audio header. They tell you whether the
> audio is mono, dual channel, stereo or joint stereo. The "dual channel"
> mode means that channel 1 and channel 2 carry separate audio and are NOT
> the left and right channels of a stereo signal.

The component descriptor (EN 300 468) contained in the EIT can
also be used to signal the content type of the audio stream.
Can't remember if it is actually used in real-life broadcasts, though.

Johannes