Re: [xine-devel] Re: How do I mute/select/replicate just the left/right audio channel?

[Darren S. <li...@yo...>]

I demand that Lucian Muresan may or may not have written...

> Reinhard Nissl wrote:
>> if a signle MPEG2 audio stream provides two languages (i. e. one language
>> on the left channel and another one on the right channel), how can I
>> select just one channel for replay?

>> A possible solution might be to mute just the left respectively right
>> channel. A better solution would be to have the choosen channel output on
>> both channels (= mono). How could this be achieved?

>> Is this a matter for an audio post plugin?

> this is not an answer to your question, but a very related wish of mine, as
> a VDR user without a FF-card (therefore using your vdr-xine plugin or
> softdevice). I also think the better solution is to output the selected
> language on both channels, this could also be applied to solve another
> problem:

> Besides dual language in left/right track MP2 audio in DVB broadcasts,
> there are lots of mono MP2 broadcasts. At least on my setup, using a
> CM8738-based sound card I can't hear anything in my external receiver amp
> hooked via SPDIF. I think it's just because PCM over SPDIF has to be
> stereo.

I see a similar problem:

  BBC Radio 5 Live: mono   => audio.device.alsa_default_device
  BBC 7           : stereo => audio.device.alsa_front_device

I'd prefer to alter just one option and have alsa_*_device (where blank)
follow this with some appropriate default, but this probably isn't practical
or even possible :-|

> I raised this problem once on the xine MLs and got no solution  yet. I
> *think* the solution for these mono tracks, in order to be audible over
> SPDIF is that there're upmixed to identical left/right,

The upmix plugin could be extended to handle this *but* you still lose out
with the mixer settings: that always uses alsa_default_device - speaking of
which, how to set this so that the mixer affects all sound devices but only
sends output to one?

> and if this is true, the same should be done with the dual language
> left/right streams, what do you think?

I suspect that that's vdr's job, although xine-lib's own DVB code needs to
handle this too. That said, why don't those broadcasters use two mono
streams instead?

As for upmix from mono to stereo - a job for the upmix plugin?

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