ALSA for audio
 

On 2013-02-24, Daniel James wrote:
In article , John
Legon wrote:
In my own installations of Win2k and XP on several computers
(including the laptop in question), I have gone to the
manufacturers' websites and have downloaded device drivers and
utilities specific to the hardware. There has been no guesswork
or making of assumptions - the OS understands the specific
hardware and works the way it is intended to.

That's not actually how it works. The OS knows nothing about the
hardware except what the drivers tell it -- if you have the right
drivers then everything should work (that's true for almost any OS, not
just Windows).

There is always a degree of guesswork and assumption-making when you
visit the vendor's website and find drivers for a gazillion models of
hardware but none that has *exactly* the same model number as yours.


Alsa on my laptop, however, has clearly failed to identify the
hardware configuration, and provides mixer controls which serve no
purpose.

Linux sound drivers are a bit more of a black art than hardware drivers
(ALSA forms a layer above the actual hardware drivers, and getting it
configured appropriately is nowhere near as straightforward as getting
hardware drivers to spot their own bits of hardware and install
themselves).

Alsa actually is the hardware drivers. pulse is a layer above alsa (like
Jack). OSS
is a different set of drivers. alsa has an oss emulation layer.

The problem is not so much that they do not play together. The problem
is that sound card manufacturers are both proprietary (I emember writing
to MAudio about their Transit card, and asking which file on Windows was
the firmware file. They wrote back and said this was proprietary
information and refused to tell me.) and irresponsible ( all feel that
they have the right and duty to make their soundcards completely
different from and incompatible with every other card out there.
They make sure that they write a driver so that their card works in
Windows, and maybe osx, but that is it.


The biggest problem here, it seems to me, is that there are competing
standards (ALSA, OSS, Pulse, whatever) and no common conventions,
interface, or utilities to make them all play (pun intended) nicely
together.

Pulse was an attempt to make a common convention, a common API that all
programs could use. Of course then it has to speak to alsa to actually
drive the cards. And of course it introduces its own layer of bugs.







By default most people want to start with a fully functioning system
- bongs and all! They have the option to turn them off if they want
- but no Windows user would expect to have to fire up a terminal
program in order to toggle a mute control for an obscure surround
sound channel which isn't supported on the machine - just to get
basic functionality for sound whether for alerts or playing music
or videos etc..

Scream at the manufacturers of your sound card.


No, with windows it's the other way around -- whenever you install it
you have to spend time turning OFF the inane jingles it likes to play to
itself whenever it starts up and shuts down (and a few more besides).

totally different layer from the soundcards.


Somewhere in between that and the ALSA default silence would be nice!

It took me some time, a while ago, to try to get sound over HDMI out of
a Linux nettop thingie ... not only was the sound muted by default on
HDMI, the software needed to unmute it wasn't installed by default.

I agree that that's not very impressive.

Cheers,
Daniel.

ALSA for audio
 

In article , Unruh wrote:
Alsa actually is the hardware drivers. pulse is a layer above
alsa (like Jack). OSS is a different set of drivers. alsa has an
oss emulation layer.

OK ... I thought ALSA went some way beyond 'mere' hardware drivers, but
perhaps not. I did mention that sound on Linux was a black art!

Until I started fiddling with lirc I would have said that sound was
*THE* hardest thing to grok on Linux!

Cheers,
Daniel.

ALSA for audio
 

In article , Daniel James
wrote:
In article , Unruh wrote:
Alsa actually is the hardware drivers. pulse is a layer above alsa
(like Jack). OSS is a different set of drivers. alsa has an oss
emulation layer.

OK ... I thought ALSA went some way beyond 'mere' hardware drivers, but
perhaps not. I did mention that sound on Linux was a black art!

It does provide mechanisms for doing things like rate, etc, conversions or
copying or mixing, etc. So, e.g., it does provide some flexibility for
someone who wants something like mixing down a surround sound stream to
stereo at a different sample rate with a different data format. Hence not
purely a 'hardware driver' in the basic sense. The challenge is to be able
to understand how to use the features it may be able to offer to get a
specific result. Lack of clear and understandable user-level documentation
means people generally have no idea how to make best use of it.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

ALSA for audio
 

Just to let people know I've updated the content of

http://www.audiomisc.co.uk/Linux/ALS...reSilence.html

slightly.

Having just done a fresh install (Xubuntu 12.04) reminded me of what a
subtle and devious PITA 'Pulse audio' can be! Even having set my alsa
default and told Audacious to use it, Pulse was resampling and applying a
volume control to the data stream in between Audacious and the DAC! The
result was downgraded sound quality for some Audacious settings and weird
errors for other settings.

Un-installed Pulse. End of problems. Bit perfect output.

So I've added a stark warning box to the page, alerting readers.

I'm lucky in having an external DAC which displays the format it is being
fed. So I could immediately see it was being given 44.1k when I played a
96k file. Anyone without such a hardware display may simply not know that
the sound was being needlessly degraded.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

ALSA for audio
 

Jim Lesurf wrote:
Just to let people know I've updated the content of

http://www.audiomisc.co.uk/Linux/ALS...reSilence.html

slightly.

Having just done a fresh install (Xubuntu 12.04) reminded me of what a
subtle and devious PITA 'Pulse audio' can be! Even having set my alsa
default and told Audacious to use it, Pulse was resampling and applying a
volume control to the data stream in between Audacious and the DAC! The
result was downgraded sound quality for some Audacious settings and weird
errors for other settings.

Un-installed Pulse. End of problems. Bit perfect output.

So I've added a stark warning box to the page, alerting readers.

I'm lucky in having an external DAC which displays the format it is being
fed. So I could immediately see it was being given 44.1k when I played a
96k file. Anyone without such a hardware display may simply not know that
the sound was being needlessly degraded.

I don't know about USB, but for others you can see what is being fed to
the h/w by doing (while playing something) -

cat /proc/asound/card0/pcm0p/sub0/hw_params

Of course the numbers may need changing to suit setup.

ALSA for audio
 

In article , Andy Furniss
wrote:
Jim Lesurf wrote:
Just to let people know I've updated the content of

http://www.audiomisc.co.uk/Linux/ALS...reSilence.html


I'm lucky in having an external DAC which displays the format it is
being fed. So I could immediately see it was being given 44.1k when I
played a 96k file. Anyone without such a hardware display may simply
not know that the sound was being needlessly degraded.

I don't know about USB, but for others you can see what is being fed to
the h/w by doing (while playing something) -

cat /proc/asound/card0/pcm0p/sub0/hw_params

Of course the numbers may need changing to suit setup.

Thanks for pointing that out. :-) I'll either add it as an extra to the
existing page, or include it on a future page.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html