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Very wierd quantise error sound

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Very wierd quantise error sound

PostPosted: Fri May 09, 2008 5:40 am
by Anonymous
Hi guys.

I have recently been talking about computers and how they deal with sound. Well....today I was recording some music and found the latency too high so I changed the ULLI settings in my Pulsar soundcard to give me a lower latency.After I had done this it allows me the option to use the settings without restartind the DSP software.
After this I reset the ASIO drivers in Cubase and got this Strange sound:

Sound MP3

This makes me question the stability of computers and how they handle audio.
Ok, eveything was ok after a reboot but why did it become this flakey.

Could anyone confirm if this is a quantisation error sound? It sounds very similar to the sounds in Hugh's "understanding digital" post.

Thanks

Re: Very wierd quantise error sound

PostPosted: Fri May 09, 2008 9:09 am
by hugol
Come on you're still talking about the process of getting the sound into / out of the computer. This requires the computer to be able to supply or retrieve data from the sound card fast enough - and yes your motherboard / CPU / sound card combination will determine the latency you can reliably achieve. If it can't keep up then you quite often get wierd digital artifacts.

It's simple if you require low latency real-time processing then your computer has to be fast enough to deal with it. That's why there are buffers on the sound-cards because computers process data in time-sliced chunks, yet audio is at a real-time fixed rate stream. If the computer doesn't get back to empty / populate the buffer in time then the real-time stream is affected.

This effect is pretty binary - if you set the latency too low you'll frequently get pops, clicks and distortion because data is too late. Set it high enough and you won't.

There is a big difference between what you were originally inferring about computers just somehow corrupting audio quality - and the low latency demands of real-time streaming and processing. AKA choose your system wisely and set your system up properly and everything should be fine. This is why DAW builders choose motherboards and other components very carefully to ensure the system performs well with low latencies.

Aside from latency getting sound in/out of a computer you obviously need to ensure you don't overload the CPU with the amount of processing you need it to do. This is just common sense.

Re: Very wierd quantise error sound

PostPosted: Fri May 09, 2008 10:24 am
by dmills
Sounds to me like some of the software didn't pick up the buffer size change and is dropping (or repeating) a few samples.

Interestingly that file also appears to have been **SHARPLY** lowpassed at ~17Khz, which lends weight to the possibility of something in the application getting it wrong.

To me, this is a case of "Doctor, it hurts when I do this...", restart your app after changing buffer lengths and everything should be fine.

Nothing really to see here (except possibly a minor bug).

Regards, Dan.

Re: Very wierd quantise error sound

PostPosted: Fri May 09, 2008 10:38 am
by James Perrett
dmills wrote:
Interestingly that file also appears to have been **SHARPLY** lowpassed at ~17Khz, which lends weight to the possibility of something in the application getting it wrong.

That's probably down to the mp3 encoding Dan.

I'd agree that changing buffer settings on the fly can be dangerous - many programs try to save processing power by making assumptions that are usually safe - like the fact that the buffer size won't change.

Cheers

James.

Re: Very wierd quantise error sound

PostPosted: Fri May 09, 2008 1:39 pm
by Teleute
I've replied to your original post as you have kind of a double posted.

http://www.soundonsound.com/forum/showf ... Post613771