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Re: Advice to an audiophobe ??



Thanks Tim;

Some of these questions were meant simply as examples of the kind of
thing I don't understand.  Nonetheless, to flesh them out:
On Wed, 2008-12-24 at 08:30 +1030, Tim wrote:
> On Tue, 2008-12-23 at 10:55 -0500, William Case wrote:
> >       * What is the difference between alsa and pulseaudio?
> 
> Major differences:  Pulseaudio can produce different sounds at the same
> time (e.g. your IM program can bleep at you while your music program
> carries on playing music, and do so without crashes, hangs, hold-ups for
> one to finish, or nasty noises), and with individual volume controls for
> each (e.g. your IM bleeps subdued, while your music may be reasonably
> loud).
> 
That begs the question, when I use the volume control gui the Device:
field gives me five options:
     1. HDA NVida (Alsa-mixer)
     2. Analog Devices AD1986A (OSS Mixer)
     3. Playback: HDA Nvida - AD198X Analog (PulseAudio Mixer)
     4. Capture: Monitor of HDA NVidia - AD198x (PulseAudio Mixer)
     5. Capture: HDA NVidia - AD198x Analog (PulseAudio Mixer)

HDA NVida (Alsa-mixer) seems to be the default.  

1. Gives me a whole range of adjustments for different channels.  (I
assume channels means different sources e.g. Master, Headphone, PCM
etc.). 
2. gives me two choices and 
3., 4., 5. gives me only Master.  
Which should I choose and why?

Help is less than useless.  There should be a man page but damned if I
can find anything helpful.  man pulseaudio has techish for installing
and setting up the backend but nothing that might be useful to an audio
newbie.

In case it helps:
]$ lspci returns 00:10.1 Audio device: nVidia Corporation MCP51 High
Definition Audio (rev a2) on a ASUS M2NPV-VM motherboard; Fedora 10,
Linux kernel  2.6.27.7-134.fc10.x86_64.

If I should be using HDA NVida (Alsa-mixer), why do I have PulseAudio
options?

> >       * What is the difference between Master, PCM, Front, Line-in, CD,
> >         PC-Speaker etc. ?
> 
> Master is the overall volume control over everything, the same control
> that you're used to on your stereo system.
> 
> PCM is just the volume control for generated sounds (Waves, MP3s, etc.).
> 
> Front is the volume control for the front speakers, if you have a system
> with front and rear speakers (3 - 5, or more, speaker systems).  Used as
> a balance control between front versus rear sound levels.
> 
> Line-in will control the volume from the analogue audio line-in in
> socket (which may accept signals from something like 0.2 to 2 volts of
> audio, compare that to microphone sockets, which may use something in
> the range of 0.0001 to 0.010 volts, i.e. there's a large factor of
> difference between line and microphone signal levels).
> 
> CD will (generally) control the volume from the (3 or 4 pin) analogue
> audio cable between the CD/DVD drive and the sound card.  Although it's
> *possible* that systems digitally decoding the audio stream from the
> data from the drive (down the IDE/SATA cable) may *also* pay attention
> to that volume control, it's generally a hardware control of the line
> input on the audio card.
> 
> PC speaker controls, if it's connected, the motherboard beeper volume
> through the sound card.  On some systems, that's a cable between the
> beeper output and a sound card input, on others its handled without
> additional cabling, and others it can't be done.
> 
> These individual mixer input controls should normally be left off if you
> never use them, as they can each introduce noise (hiss, beeps and
> burbles, etc.) to the system.  

I will turn them off except for Master and Front.  I will experiment
with PC Speaker.  Of course these are only available to me if I use the
default alsa mixer setting.

By the way, I have a Multimedia Systems Selector frontend which gives
various perms and combs which don't make sense given the above remarks
and which 'help' says to leave alone if you are not an advanced user
which, obviously, I am not.  The test beep seems to work on just about
any combination.

There is also a sound preferences gui that is set to autodetect that
seems to also test out with any setting giving a long beeeep.

It is all very confusing.

> And when you do use them, it's dependent
> on the card whether the nominal position for the level control is all
> the way up (for simplicity's sake), or part way up (allowing you to
> listen to signals that are really too low in level).  And again, there's
> variances as to where the partial position may be (e.g. half way, or
> three quarters up).  Also, what's connected to the mixer plays a role
> there, whether it has a low output level that will need boosting, the
> same level as the card expects, or a high level that will normally be
> too much.
> 
> >       * How is sound related to video ?

> Sound is the sound, video is the picture...  The question is too vague
> to be answerable.
> 
Sorry, I didn't mean to be vague.  Most of my sound problems over the
years seem to have been related to sound that goes with video of
different kinds - Flash being the most recent.  The solution for me has
always been trial and error or to get advice from the mailing list.  And
then just button push without having a clue as to what I was doing.  I
wanted to read some overview that would give me a fighting chance to
diagnose problems myself.

> >       * Why are there so many files associated with producing sound?
> 
> Driver-wise, there's a plethora of different sound cards, which all work
> very differently, and each have differing controls available to the
> user.  There's a plethora of different audio codecs.  For playing MIDI
> files, something needs to generate the actual sounds each note will play
> (that could be one file per sound, or you could make use of hardware
> that does it).
> 
> That's another almost unanswerable question.
> 
Yea tell me.  It wasn't a question I expected answered individually.
But I have noticed that every time I install something involving sound I
get any number of files as dependencies.  A few Fedora versions ago I
uninstalled Alsa for some forgotten reason and it ripped out almost my
entire system and I had to re-install the whole Fedora.

I thought someone might have written up a manual on sound basics to
explain all this.  For example, I have looked at The Linux Document
Project for something useful but all the documents are howto's with
little emphasis on why or what.  From what I read, I was left with more
questions than answers.
-- 
Regards Bill
Fedora 10, Gnome 2.24.2
Evo.2.24.2, Emacs 22.2.1


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