[pulseaudio-discuss] [PATCH] Add HDMI Surround 7.1 profiles

[David Henningsson]

On 2014-07-13 12:45, Tanu Kaskinen wrote:
> On Sun, 2014-07-13 at 15:07 +0600, Alexander E. Patrakov wrote:
>> Signed-off-by: Alexander E. Patrakov <patrakov at gmail.com>
>
> Looks good to me, but I wonder whether there was some reason for not
> having a mapping for 7.1 when there already was a mapping for 5.1.
> Before applying the patch, I'd like to give David a chance to comment
> (he's on vacation for the next week).
>
> Somewhat related, I also wonder why the surround mappings (both 5.1 and
> 7.1) are only in extra-hdmi.conf. My understanding is that the point of
> extra-hdmi.conf is just to offer the additional mappings for the
> subdevices 1-3, so the non-extra surround profiles should be copied to
> all other profile-set files too.
>
> And still one related note: it seems that 5.1 mappings are missing for
> the "extra" subdevices.
>
>> P.S. should I also upstream profiles that allow sending software-DTS-encoded
>> stream to HDMI?
>
> Probably yes.

Every new profile added is a trade-off: It takes some extra time (at 
startup or hotplug) to probe a profile. And we want computers to boot as 
fast as possible.

Adding new profiles will increase the functionality but at the expense 
of longer startup time for everyone, regardless of whether they'll 
actually ever use that profile.

That's the original reason why there is one extra-hdmi profile in the 
first place, to avoid extra time being spent probing hdmi stuff on e g 
USB headsets.

That said, I think it makes sense to make some additional measurements. 
If we get stopped at the alsa-lib layer (e g because the "hdmi" name 
does not exist), then maybe there isn't much overhead to consider.

So, it probably makes sense to
  * Merge extra-hdmi.conf into default.conf
  * Merge this patch as well
  * Allow up to 8 hdmi devices (alsa 1.0.28 has this addition)

...but the question is how much additional overhead this will mean for 
analog built-in audio, USB headsets, etc. Anybody who wants to do some 
research on this topic?

-- 
David Henningsson, Canonical Ltd.
https://launchpad.net/~diwic