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Re: PulseAudio

On 07/18/2013 01:00 AM, Wouter Verhelst wrote:
They're both APIs that applications can use to produce audio. What do
you mean, it doesn't make sense?

Of course they're not the same thing; I get that. That's not what I'm
saying. But as far as "producing audio" is concerned, they can both do that.

PulseAudio is not a stand-alone thing, it doesn't work without an
actual abstraction layer for the sound hardware like ALSA.

When you compare PA, you should compare it with artsd, esd, dmix
or JACK, but not the low-level layer below.

PulseAudio piles another layer of possible failures on top of a kernel
driver, and hides most of the audio mixer for no particularly good
reason other than "it might confuse the poor user". It just doesn't make
any sense to me.

Some sound cards expose two dozens or more level adjustments which most
people don't even understand.

I've never seen a setup where there wasn't a "master" mixer.

Which often doesn't help if some other adjustment has been turned off
or set to a very low level. I have sometimes been debugging for hours
trying to figure out how to mute a certain channel or select it for
recording in ALSA. It's not always obvious and different for every
single soundcard model on the planet which is one of the reasons PA
was written in the first place. A canonical, consistent interface to
configure your soundcard.

There were just way too many options and level adjustments exposed,
many of them with many obscure names when you use plain ALSA. I don't
think that most users know what "IEC 958 - ON/OFF" is supposed to mean.

I've never seen a setup where there were more than a handful of mixers,
except on an expensive piece of hardware meant for audio professionals
(or advanced hobbyists). I doubt such people would like to see their
expensive hardware reduced to a single mixer.

Well, back when I still had a SoundBlaster AWE64, there were something
like 5 adjustments in total. 4 for each input and output and one master
adjustment. However, ever since AC97 or even HD Audio was introduced,
the number of adjustments just exploded and, as I said before, the
names are usually quite obscure.

Sure, it's fine when you're an advanced user and you know what you're
doing. But for an average Joe the whole ALSA mixer setup is just a

I don't think it's a bad idea in general
to clean that up and make the whole interface more consistent and
easier to understand.

Not contesting that. It's just that every time pulseaudio got pulled
onto my system, my audio stopped doing what it was supposed to. That's
not what I would expect from something that's supposed to make things
"easier to understand".

Could you please stop coming up with anecdotes and actually describe
some real situations where PulseAudio messed up due to a bug?

I often hear such statements from PA antagonists, but I am yet waiting
to read an actual bug report.

However, if you have more than one sound device, PulseAudio is a
blessing. For example, my video card has an HDMI output. When
I hook up my PC to my television via HDMI, I want the sound from
VLC to go through HDMI rather than through my sound card. It's
a matter of opening a preferences pane, change the output device
to HDMI and I am done.

That's something you can do with plain alsa, too.

I have no doubt that you can do it in ALSA as well. The question is,
however, whether it involves a 20-hour heart surgery as opposed to
just opening a panel with PA and changing the default output for
a specific application.

It's about usability. Not whether it's feasible at all or not.

How do I do that with just plain Alsa without using a text editor?


ctrl-p, go to the audio tab, and select the correct device in the
"output" frame.

That's not VLC-specific, FWIW; most applications that can do alsa output
have a way to select the output device. There are exceptions, of course,
but those applications are either immature or buggy.

Which means there is no canonical way to do it, and, like you said not
every application supports such an option.

Do I really elaborate why a central control panel to configure that is
the superior solution instead of having to figure out for each and
every application how to do it?

Even so, there's no reason why there can't be a tool to edit an asoundrc
file... but you don't really need that, in my experience, since most
applications allow you to choose the correct output device.

Again, *most* is not all and no, I don't want my mother to open up
a text editor and having to write some obscure text lines in order
for her to get the audio on her television after she connected it
to her television. Do you know how hard that is to explain something
on the phone to someone who is not a computer aficionado?

Seriously, she already found it confusing how she has to import
photos from her digital camera in Shotwell. And now you want me
to explain her that for such a basic configuration option she
has to figure out how to do that for every single application
that is using sound?!

What do I do when I want my Skype input going through the USB
webcam's microphone and the audio of Skype through my bluetooth
headset instead of my primary sound card?

You select the correct input and output devices in skype...

Ha! I am pretty sure you haven't used Skype and ALSA extensively
in the past.

You just don't select the proper output and input devices in
Skype. You actually have to go to ALSA mixer and tell ALSA
that you actually want to *record* from the microphone
connected to the front panel or the back panel. Otherwise the
signal is just passed through the sound card meaning you can hear
your voice but Skype does not record it.

I spent endless hours before I figured that out. And that was just
one of the problems. Very often Skype would just block or crash
when trying to configure audio. It wasn't until they ported
Skype to PulseAudio when it actually became usable on Linux.

I am sorry, but in my eyes, people who claim that PulseAudio is useless
simply don't realize that there can be sound setups which are a little
more sophisticated than just a single sound card and configuring
these can be PITA when you don't have PA.

That simply does not match my experience.

Well, I am sorry if that's not the case for you, but it is obviously
the case for the majority of our users, otherwise the pulseaudio
package wouldn't be so popular [1].

Either all these people don't care about broken audio or PulseAudio
*does* actually work the way it's supposed to work.



> [1] http://qa.debian.org/popcon.php?package=pulseaudio

 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz@debian.org
`. `'   Freie Universitaet Berlin - glaubitz@physik.fu-berlin.de
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913

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