> You are of course throwing resolution away if you use the 7-bit or 6-bit
> modes. The low bit(s) are just gone. In 9-bit mode the extra bit is just
> "invented" by the system so it's still just 8-bit sound.

Well, I thought I explained this. The reason that argument is not calid can
be attacked from two different angles:

1) If you move from 8-bit to 9-bit, though you gain resolution in sample
depth, you lose resolution in sample rate. That extra timing bits are, to
quote, "just gone".

2) The sound card pushes the same amount of data per second no matter what
mode you're in, implying that no loss of resolution has occurred, but rather
a shift in resolution.

Here's a hint: don't say "of course". That's a really dangerous phrase,
especially when your substantiation of why rigorously ignored half of what's
going on.

> In 9-bit mode the extra bit is just
> "invented" by the system so it's still just 8-bit sound.

Can anyone confirm this? This seems ludicrous to me, and I've never seen
anythign which supports this. Moreover, when I generated tones through the
AGB, I was able to tell the difference, when using waveforms whose timing
was adjusted to be different.

That said, there's been some indication on the list that a waveform expanded
to fill different timing rates somehow sounds different, so I worry that
that's what I'm hearing.

The nine bits of data *are* being interpreted by the system. Otherwise,
that ninth bit I put in the waveform should have wreaked havoc, and it
didn't. Moreover, 8-bit data filled in in the 9-bit mode sounds completely
wrong, leading me to suspect that you're just making that up.

> The balance between sample rate and sample depth is most elegantly exposed
> using PWM. Roughly speaking, you can double your sample rate and half
your
> dynamic range [= drop 1 bit from the sample depth] and the sound quality
is
> equivalent [i.e. identical, assuming proper analog output stages].

Instead of picking on the grammar here (start with a question, end with a
statement attatched with an "and"), I'm gonig to point out that

a) sound quality is *certainly* *not* equivalent, and if you were to try the
MP3 experiment I described, you'd know that, and
b) if it were equivalent, how could you possibly be losing resolution?

> PWM is
> essentially 1 bit at very high speed, and it *emulates* 8 bits and 65kHz,
or
> 9 bits at 32kHz, etc. There is no reason to choose one over the other in
> principle because the DATA RATE is the same, and it's data rate that
counts.
> However, the analog shaping circuitry at the output stage makes a BIG
> difference here. Not knowing what the output stage is exactly, the only
> valid advice is to try the different modes and choose the one that sounds
> best.

Uh, no. While it is true that PWM is a 1-bit signal constructed into
varying rates, there are absolute scads of logical errors. If the sound
quality is equivalent, what's this about testing to see which sounds best?
And what makes you think that it cannot be predicted what effects sample
rate and sample depth will have on a sample?

> I don't understand where FM comes in. GBA uses Pulse Width Modulation,
not
> Frequency Modulation. FM uses sine waves; PWM does not.

Brain fart. I tend to use FM to mean sampled sound, because most people
recognize it that way, much like I tend to use Hacker to mean Cracker, even
though the word is just wrong. That said, this is a technical forum and I
shouldn't have. My bad.

> Another hint from DSP theory: if you calculate the sounds internally at
> higher than 8-bit resolution, then you should add a certain amount of
noise
> [dithering] before you cast the sample to 8 bits. The dithering should be
a
> random amount between -0.5 and +0.5. The difference is marginal at 16
bits,
> but at 8 bits it is audibly noticeable. In experiments, it has been found
> that people can hear a sine wave that is only 1/2 LSB large AS A SINE WAVE
> when 1/2 LSB of noise is added. Without the noise added, all you hear is
a
> SQUARE wave. That's a big difference at low amplitudes. Think of how a
> greyscale image would look with and without dithering - your ear works the
> same.

Um. I'm not a sound technician. +0.5 what, and -0.5 what? Why would
adding noise make something sound better? Is this to combat aliasing? If
so, why not just approach the aliasing from a known position? Certainly
there's something better than randomness. For that matter, if random noise
is good, why are uninsulated cables bad? They're not getting very much
amplitude compared to the real signal at all, and though +0.5 has *no*
*unit* (this is bad, 3rd grade math), I'm assuming you mean against a signal
level of one. I don't know whether line amplitude is measured linearly or
logarithmically, but either way, I'd be hella surprised to learn it went
over 0.5 on a scale of 1 unknown unit.

That said, unless you're a sound engineer, that paragraph is completely
incomprehensible. And I'm kind of hesitant to believe that a sine wave,
when played wihtout noise, sounds liek a square wave when listened to. Or
whatever you meant.

Look, you seem to know a lot about the topic, but what you say is
self-contradictory. Let's put the debate to rest: the amount of data flow
is unchanging, and there is no compression involved, so there is no
resolution loss. This is very simply put. The sample rate can have a
difference in resolution, *or* the sample depth can have a loss in
resolution, but the sample itself cannot, as the rate and the depth will
mirror each other.

If you're discarding sample rate, then yes, sample depth can lose
resolution, but that seems to me to be a clearly erroneous thing to do. The
bitrate is unchanging, and I'd like to see you address that.

In the meantime, what's all this about random noise making things sound
better? If you mean that the dither pattern has a random component, that's
different, but those aren't random - tehy're pseudo-random, and in the case
of dithering patterns, not very - they have rules regarding neighbors, etc.
That's very different than random noise and should not be presented as such.

Dithering seems like entirely the wrong word to use, by the way. Dithering
is a term used specifically to refer to graphics, especially bitmap
graphics. It comes from the old english word, meaning to shiver (merriam
webster online comes up with that one; the better definition can be found at
FOLDOC.org).

Now, I'm not claiming to know how people on the inside of the digital audio
industry talk about things, but I think it's curious that every single one
of the pages I come up with uses the phrase "anti-aliasing".

So, look. Your last message neatly restated what you said before, but did
not address any of the concerns I raised as to why I think you're wrong, so
I still think you're wrong. If you have a good way of demonstrating to me
that the *total* resolution - sample rate and sample depth - is changed by
this operation, I'll take it. Do remember, as I keep restating, that the
data rate is unchanged.

For the sake of this list, I'm gonna drop the thread, unless his new reply
actually addresses some of these topics.

- Fatty the somewhat annoyed
("of course" indeed)


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