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Author Topic: Sound sampling rate - what does it do? ~ANSWERED  (Read 1237 times)

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Messer

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Sound sampling rate - what does it do? ~ANSWERED
« on: November 02, 2009, 06:51:27 AM »

Hey, sorry for the (probably) stupid question. I just downloaded a few SAS soundpacks (for the 190s and the Allison engines) and I noticed that in all the readme's the sampling rate was set to 22khz.

My Il-2 setup is set to 44khz (max supported), while my Xonar DX audio card is set to sample at 192khz PCM ~ trough to a reciever (I guessed more is better). So, if the in-game samples are set to 22, the game process them at 44 and then the sound card at 192khz... what? Does that lead to sound distortion, missing sounds, cracking etc? Or just workload for the CPU and it doesn't affect quality at all?

Sorry, audio systems have never been my passion. :) I hope someone can explain this....
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Paulo Hirth

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Re: Sound sampling rate - what does it do?
« Reply #1 on: November 02, 2009, 07:54:51 AM »

  Cirx set 22mhz to SAS... but i will sugest 44mhz, because better quality and work ok in modern onboard soundcard too.
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SAS~CirX

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Re: Sound sampling rate - what does it do?
« Reply #2 on: November 02, 2009, 09:14:26 AM »

it will increase the workload of your DD and DA converters a bit. The quality of Sampling rates is in the modern world very much a "emopor's new clothes" thing.

What advertising makes you believe is one thing, while reality is somthing else. While one can hear a difference between 22K and 44K, it is very content dependant. And in the case of engine sounds only noticable in the higher frequency and harmonic ranges where you enter into the area of the nynquest theorim. It makes little difference with a primarlily low and mid freq engine sound, but having it at 22K effectively halves the ammount of data your machine has to munch. Making the sounds mono again halves the workload once more.

Setting your game sound at 44K means that the game itself is doing the initial conversion for you before passing it out to the CPU, and since conversions from 22050 to 44100 is a "clean" conversion, it is not such a big deal. So you dont have to worry.

And if your setting at your card side is not causing you issues, then it is also OK.The card setting  is the sample rate wat which the card then resamples all outgoing signal to send a "higher fidelity" signal to your amp. But since what it is resampling is substantionally smaller than it's setting, all you will hear extra are digital occurenses particular to that card. Many commercial soundcards today are "tuned" to the playing of mulimedia formats, in which you have varying rates and bitdepths and compressions. So, handling this again should not be a problem.

In short, if it is not broken, dont fix it!

Distortion is an effect of pushing a processing step with a suprior amplitude setting into a step that does not have headroom to accomodate it, causing it to "clip" the tops of the pulses. In analogue this can be quite nice, and is the principle behind the electric guitar amp. One preamp you will boost (or "drive")the signal, while turning down the input capacity of the preamp input of the next amp, so it cannot handle the signal it receives properly, causing distortion (overdrive).

In digital world distortion is very bad and ugly though. Digital SP ends at 0db, and one has to make things louder then by applying compression in multiple bands and clever eq and bass handling and such, to make it "sound" louder, without going over 0. because 0 is the limit of the adressing capacity of the bitdepth sampling envelope. it gets realy interesting from there on. But anyway, this is the reason digital recordings are often mastered to a flat top, with very little dynamic range. These days one has to considder the compression and mix parameter from the first instrument you record for a piece, because compression changes the mix, and one cannot compress so colorfully as you could with tape.

So if you gather distortion, it is because one of the steps in your chain is overboosting. Boost has to be the largest at the end line (amp,) and the smalles at the start, so it slides upwards naturally.

In IL2, cracks and pops are normally cause by the limitations of the soundengine  (this will appear as a soft click when switching from outside to inside view) or ill dicipline when compiling samples (continious popping and crackling in a specific view). This is because of mixing stereo and mono sample, samples of sifferent sample rates, but depths ect. Also, even if you dont get the artifacts, just having such a mix of media parameters loads your PC work a lot.

As an example, look at the recent UI1.2 samples folder.

Have a look at the samples folder. Look at it in "detailed" view, and choose then to view the arrtibutes of "Bit Rate" "Audio Sample Size" "Audio Sample Rate" and "Channels"

You will see what a bad mix of formats are thrown together there.  12 diffent types of bitrate! All Sample Size is 16bit except 1 24 bit file that has to work with 16bit files in Packard merlins, 9 different types of sample rates! And mono and stereo files all mixed together.

In the SFS mod we made, all is mono, 16bit, 22K and 352kbps, except the sound for rain and for the zenitka, which we left at stereo.

So regardless of your setting in game or at card, your machine is going to be much happier and healthier.
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SAS~Malone

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Re: Sound sampling rate - what does it do?
« Reply #3 on: November 02, 2009, 09:33:51 AM »

The sound-meister has spoken.... :D :D ;)
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CoolBreeze

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Re: Sound sampling rate - what does it do?
« Reply #4 on: November 02, 2009, 10:27:06 AM »

Great explanation. I love when CirX talks dirty. ;D
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Flanker35M

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Re: Sound sampling rate - what does it do?
« Reply #5 on: November 02, 2009, 11:11:48 AM »

S!

 Sucha dirty man he is ;) Playing his black bitch all day..:P
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