[pulseaudio-discuss] Mono Upmixing Only

Carl Gridley crgridley at gmail.com
Wed Apr 3 02:20:43 PDT 2013

Wow, wasn't expecting code so quickly - thanks!

I've been away for a bit. Is this working and done? Do I need to get PA 3
and a patch on my system or is it all good and in the queue for an offical
release in the future?

Many Thanks

On 21 March 2013 09:45, Carl Gridley <crgridley at gmail.com> wrote:

> Hi Tanu,
> Thanks for replying :-)
> When upmixing is disabled, mono playback is silent but does not generate
> errors that I can see from pulseaudio -vvv or any notifications.
> Here's a bit of output:
> I: [pulseaudio] source-output.c: Trying to change sample rate
> I: [pulseaudio] source-output.c: Resampling enabled to 44100 Hz
> D: [pulseaudio] module-suspend-on-idle.c: Sink
> alsa_output.pci-0000_01_00.1.hdmi-surround-extra1 becomes busy.
> D: [pulseaudio] resampler.c: Channel matrix:
> D: [pulseaudio] resampler.c:        I00   I01   I02   I03   I04   I05
> D: [pulseaudio] resampler.c:     +------------------------------------
> D: [pulseaudio] resampler.c: O00 | 0.000 0.000 0.000 0.000 0.000 0.000
> I: [pulseaudio] remap.c: Using generic matrix remapping
> I: [pulseaudio] resampler.c: Using resampler 'peaks'
> I: [pulseaudio] resampler.c: Using float32le as working format.
> D: [pulseaudio] memblockq.c: memblockq requested: maxlength=33554432,
> tlength=0, base=12, prebuf=0, minreq=1 maxrewind=0
> D: [pulseaudio] memblockq.c: memblockq sanitized: maxlength=33554436,
> tlength=33554436, base=12, prebuf=0, minreq=12 maxrewind=0
> I: [pulseaudio] source-output.c: Created output 14 "Peak detect" on
> alsa_output.pci-0000_01_00.1.hdmi-surround-extra1.monitor with sample spec
> float32le 1ch 25Hz and channel map mono
> This particular one is from a mono youtube video played in Chrome, the
> behaviour is the same in other applications too.
> For the plans comment, this is just a quote referring to fine-grained
> control over upmixing from this thread:
> http://lists.freedesktop.org/archives/pulseaudio-bugs/2009-December/003553.html
> That was several years ago though.
> I think your option would be good, to make sure I understand it it would
> be:
> - no upmixing of stereo sources (or any multichannel source) with the
> upmix module disabled
> - mono would still be upmixed (probably to all channels) regardless of the
> upmix module being active or not
> Or something functionally equivalent to the above.
> If I can help with testing I'm happy to try any patch on my system.
> Cheers
> Carl
> On 21 March 2013 07:58, Tanu Kaskinen <tanuk at iki.fi> wrote:
>> On Wed, 2013-03-20 at 10:34 +0000, Carl Gridley wrote:
>> > Hi folks,
>> >
>> > I have found some old messages on this, but wondered if anything had
>> > changed or anyone had any bright ideas on it now :-)
>> >
>> > I have PA 2.1 running on Kubutu 12.10.
>> >
>> > It is connected via HDMI to my AV receiver and so I have 5.1 PCM output.
>> >
>> > I've got two music speakers, and the surround speakers are much
>> smaller, so
>> > I turn 5.1 upmixing off. I also turn off LFE mixing as the receiver
>> does a
>> > good job and can set a crossover per channel.
>> >
>> > Everything sounds great, but mono sounds don't work as they can't get
>> > upmixed to stereo. If I re-enable upmixing, mono works, but then all
>> stereo
>> > sources get upmixed which I'd prefer not to.
>> I haven't bothered to try this myself: how do mono streams behave when
>> upmixing is disabled? Does the stream fail to connect to the device, or
>> does it connect but is silent, or something else?
>> > I know from the previous notes there were no plans to allow more control
>> > over upmixing, has this changed at all?
>> No plans in what sense? Patches for enabling sensible use cases will be
>> accepted, and this use case definitely is sensible. If you mean "no
>> plans" as in "nobody has promised to do the work", then you're right,
>> and nothing has changed.
>> > An option just to enable mono
>> > upmixing only would be fantastic :-)
>> >
>> > Or even map mono to the centre channel if one is reported.
>> I'm not sure there is need to have any new options. If mono streams
>> don't work at all in case upmixing is disabled, I don't see why anyone
>> would want to keep the current behavior. We could have a special case
>> for mono-only streams so that such streams would always be upmixed to
>> all channels (or some smart selection of a subset of the available
>> channels, but all channels is easier to implement).
>> I looked at the remixing code to determine what it would take to
>> implement this, and it seems simple enough that I'll write a patch
>> myself.
>> --
>> Tanu
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.freedesktop.org/archives/pulseaudio-discuss/attachments/20130403/1d11d885/attachment-0001.html>

More information about the pulseaudio-discuss mailing list