[pulseaudio-discuss] Conditional up/down mixing

[Lennart Poettering]

On Mon, 28.12.09 14:49, Colin Guthrie (gmane at colin.guthr.ie) wrote:

> Hi,
> 
> I could have sworn this was asked about on the ML recently but perhaps
> it was just IRC as I cannot for the life of me find the message :s
> 
> Anyway, someone was asking about their 5.1 capable card and how they
> would prefer that stereo streams were not upmixed as their sound
> receiver does a better job of upmixing (e.g. Dolby ProLogic or similar
> gubbins).
> 
> I was thinking about this today and I think this is a pretty common
> setup. I think I may actually have need to do that in my own setup now
> I've finally gotten around to configuring it up in a vaguely working way!
> 
> So what I was thinking was some way to defining the mixing profile (via
> simple module argument) that simply lists (comma separated) the channel
> counts that are permitted for remixing.
> 
> The remix = yes/no still works too but inverses the logic of the
> remix_profile argument.
> 
> e.g. remix="yes" remix_profile="2" means it will *not* remix 2 channel
> sound to the sinks channel count.
> 
> whereas remix="no" remix_profile="1,3,4,5,6,7,8,9,10"  means much the
> same thing, but only as far as 10 channels.

Isn't it a bit ugly if one config options completely reverses its
meaning depending on another one?

> Obviously remix_profile is fully optional and remix= works as currently
> if specified on it's own.
> 
> I've not analised how the code works to see how much hassle this would
> be to implement, but if this sounds like a vaguely sensible idea, I'll
> look at cooking up a patch.

Hmm, IUC the use case for this is that mono→stereo upmixing should
always be done while stereo→5.1 and mono→5.1 upmixing should not be
attempted, right?  And that this means that if you play a mono stream
you need to upmix it to stereo on a 5.1 device right?

That use case complicates things considerably sincei its not just
about saying remixing yes/no, but about saying: if remixing from "A"
to "B" is requested actually do "A" to "C", with "A" != "B" and "B" !=
"C", if you follow.

Lennart

-- 
Lennart Poettering                        Red Hat, Inc.
lennart [at] poettering [dot] net
http://0pointer.net/lennart/           GnuPG 0x1A015CC4