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Re: Advice to an audiophobe ??



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).

>       * 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.  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.

>       * 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.

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