The aliasing thread

Sampler and Sampling discussion (techniques, tips and tricks, etc.)
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autloc wrote:Low sounds the same to me as "poor". Why not just say "noisy" and "clean"?
I personally prefer high/average/low, although noisy and clean seem equally valid too. Maybe interpolation naming would make more sense, but unfortunately there are some samplers giving no details about this.

But I'm still amazed how many products, even new ones, are still using linear interpolation :(

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What about removing the "high, average, low" or "good, medium, poor" or "da bomb, so-so and shitty" cathegorizations completely?

After all, aren't the limits between cathegories subjective?

-René

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autloc wrote:
Muon Software Ltd wrote:No, not at all. They're not LTI processes at all and can introduce spectral elements not in the original signal.
I think we must be talking at cross purposes. The equation y[n] = 0.3*x[n] + 0.7*x[n-1], for example, (a linear interpolation or 1st order FIR) cannot add spectral components.
autloc, the part you're missing is that those coefficients (0.3 and 0.7 in your example) change from sample to sample and are very dependent on the relationship between the sampled rate and the playback rate. That part makes them not LTI.
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Don't do it my way.

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René wrote:After all, aren't the limits between cathegories subjective?
Agreed.

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george wrote:
René wrote:After all, aren't the limits between cathegories subjective?
Agreed.
The great value of those graphs is that they give you a (relatively) objective measurement of interpolation noise. As such, and for political reasons, it's probably best to avoid any subjective labeling on them entirely. Also, you might want to add a brief summary of the better points raised in this thread. Something like "keep in mind that resampling fidelity is only one aspect of synthesizer quality, and any of these instruments is 'good enough for rock'n'roll.'"
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Don't do it my way.

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René wrote:What about removing the "high, average, low" or "good, medium, poor" or "da bomb, so-so and shitty" cathegorizations completely?

After all, aren't the limits between cathegories subjective?

-René
I am like manymany other users (owning products by George, WilliamK and the wonderful sfz+ and others from René) just beginning to understand what this all is about :D . Well, actually it's a lie, I downloaded all the pages (mostly before sentences were deleted maybe, I don't know) to understand what could be meant and hope to know it tomorrow :D .

But the last post by René is the best in this thread, methinks. Quite right for all of us philosophers 8) and musicians round here :D . It's not only stoicism in philosophy, we learn here :D.

I completely agree too that those threads (and the funny link from Ben/KVR :hihi:) are wonderful for users. Not because of the bashing, of course, but because that's the right words to read and read again and(in my case) maybe understand in some time and then goin' back to your vsti-s and see what you can make of it.

Cheerio.

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autloc, the part you're missing is that those coefficients (0.3 and 0.7 in your example) change from sample to sample and are very dependent on the relationship between the sampled rate and the playback rate. That part makes them not LTI.
right, i agree - that's why there's aliasing with sample rate conversion but not with a constant fractional delay. i was just trying to say that "linear interpolation" or "hermite interpolation" do not necessarily alias. in fact, when used for delay lines (unless there's constant adjustment to delay line length) there is no aliasing at all.

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Adding some fuel to the fire, and to reinforce rene's quoting about 16 vs 12 bits wars time ago (cool), i remember when Nintendo's N64 gaming console was released, it has bilinear interpolation for texture mapping. Half community of the gamers complained that its graphics looked dull compared to sony's psx1, wich just used 'nearest' interpolation for texture mapping... :P

I wonder how many games are released nowadays without bilinear interpolation texture mapping at least in its minimun ?quality? settings.

The fun really starts here: 8x or 16x oversampling in realtime 3d rendering will be the bread and butter of games in a few years, and i'm sure no hardcore gamer in the world would argue that no-oversampling helps for a better gameplay experience (mm... at expensiveness of Frames Per Seconds, always fine with a minimun of 60fps).

:D Maybe in 50 years we have sinc texture mapping.

In the other side: who doesnt like playing those old lovely games with 'aliased' graphics in emulators.
:lol:

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when used for delay lines (unless there's constant adjustment to delay line length) there is no aliasing at all.
In this case the linear interpolation primarily has an impact on the frequency response (specifically lost of high treble). So I guess you could describe this action as being consistant with a filter. Guess we are indeed talking about the same thing :D

Cheers
Dave

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Why do I percieve everyone so cute now. I somehow miss something, so let's do something about it.
keep in mind that resampling fidelity is only one aspect of synthesizer quality, and any of these instruments is 'good enough for rock'n'roll.'"
Perhaps you meant tarnce? Only girly rock'n'rollers use samplers.

Adding some fuel to the fire, and to reinforce rene's quoting about 16 vs 12 bits wars time ago (cool), i remember when Nintendo's N64 gaming console was released, it has bilinear interpolation for texture mapping. Half community of the gamers complained that its graphics looked dull compared to sony's psx1, wich just used 'nearest' interpolation for texture mapping...
That's bullshiet. Everyone and his 6-yo sister does know that psx1 eats n64 alive even on sunday mornings.

-René

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double on sunday mornings! nothing cures a hangover like psx1.

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george wrote:I personally prefer high/average/low, although noisy and clean seem equally valid too.
Or you could invert the relationship:

- Low Aliasing (= clean)
- Medium Aliasing
- High Aliasing (= noisy)
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:D :D :D :D
Lol rene, true man...

PSX1 Castlevania (Symphony of the night) best game ever!. (With best soundtrack)

But N64's goldeneye was... :o

Mejor que el spectrum nada.

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i remember when Nintendo's N64 gaming console was released, it has bilinear interpolation for texture mapping. Half community of the gamers complained that its graphics looked dull compared to sony's psx1, wich just used 'nearest' interpolation for texture mapping...
I think it was more because the N64 had no memory, so textures were tiny and very blurred when looked close

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Ok. To start facing the 'how much the graphics represent audio quality', I've prepared a few audio snippets. I believe they might help.

All the audio snippets have a violin major third, transposed in different intervals. They all compare Linear interpolation with Bicubic interpolation. All tests were rendered in sfz.

The first test is transposing the sample down two octaves. I agree that this is quite out of 'standard' or 'used' transposition ranges, but it helps a lot to first hear what we're looking for very clear to then move to more subtle examples.

http://www.rgcaudio.com/downloads/other ... oct-dn.rar

Ok. I believe everyone here will be able to percieve the noise we've been discussing about. If you can't, please ignore the rest of this post. Perhaps it's time to get a new soundcard or speakers :D

If you can percieve it but you think the linear wave sounds better, that's cool as well. The important thing is that you hear the difference.

The second snippet shows the same scenario, but now the transposition level is 5 semitones down. This is a very commonly used interval. For SoundFonts and Akais, for instance, one-octave transposition values are pretty common. This is about a half.

http://www.rgcaudio.com/downloads/others/vln-5st-dn.rar

Ok. If a difference between both samples is not really noticeable for you, there's nothing wrong. I performed the test to 5 non-musically/technically trained persons here, and only two were capable of hearing it. But if it -is- noticeable, let's take the next challenge.

http://www.rgcaudio.com/downloads/others/vln-2st-up.rar

Now the transposition is one whole tone up. I won't comment on this one, I'd like to know what you hear.

No tricks, no hidden stuff, nothing 'fancy'. Just trying to translate from graphics and numbers to sounds and perceptions.

If this thing is somehow accepted, I can prepare other snippets with some other material.

-René

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