A few notes on the new 64 bit mode

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KVRist
55 posts since 24 May, 2005 from Germany

Post Sat Nov 26, 2005 4:54 pm

Hi all!

We are happy about the positive response to our latest release of the ArtsAcoustic Reverb 1.1 and its new 64 bit mode! So, we thought it might be useful to open this thread giving you some background information to the new 64 bit feature, as well as a few tips and hints how to use it. Also, discussion is appreciated!


What’s the technical background

To generate a reverb effect, lots of calculations have to be done. Traditionally on native systems, they have been done with 32 bit precision, which seems to be quiet a lot. The truth is, 32 bit is good, but not best. Why? Each time, a calculation is done by the CPU, very slight rounding errors occur. Normally, this doesn’t matter. But especially when dealing with recursive structures, where recent calculation results are used to calculate new results, rounding errors will be carried on and so can influence the overall result significantly.
You can compare this to the following example: you tell a friend that a well known reverb costs 189,-. He tells a friend that he should spend about 190,- for an excellent reverb and his friend tells another friend a pretty good reverb should not cost more than 200,-. As you can see, the result means still the same thing, but not exactly. This is similar to 32 bit. In 64 bit, it is like if the friend of the friend of the friend would still know the exact price of 189,-.
However, the 32 bit differences are much smaller than in our little bit far fetched example...


What’s the effect on sound quality

From the developer’s sight, the reverb calculates now more that way it was intended by himself. Means, the reverb finally does the thing he wanted it to do. From a producer’s sight, the reverb gains on transparency, spatiality, depth of field, smoothness, whatever it can be called. You surely will find your own words, but one thing is definite: it has a noticeable improved sound quality.
Of course, the difference is not dramatic. But we feel, working on 32 bit compared to 64 bit is a bit like looking through milky glass or a mosquito net.

Consider to test this for yourself by taking a mix and listen to it, when the reverb is switched to 32 bit. Then listen again with 64 bit. Tell us what you found out!


What’s the effect on CPU load

Actual CPUs can process calculations in double precision (= 64 bit), which are much more precise. So, why not do all the algorithms in 64 bit? The reason not to do so would be the higher CPU load. The reason to do it anyhow is, the errors can be reduced drastically and so the overall sound can be improved considerably. Fortunately, actual CPUs can do 64 bit calculations with not so much more CPU load and that’s why we decided to rewrite our whole algorithm for 64 bit and let the user decide whether he wants to render in 32 or in 64 bit.

In other words, you will notice a slightly higher performance need when working in 64 bit mode on actual CPUs. How much, that depends of your system. Older CPUs, like Pentium II, might cause much more load in 64 bit than in 32 bit mode.



When should I use the 64 bit mode

If your CPU is fast enough and you’re not running out of capacity, then always use 64 bit. We don’t think you will find 32 bit sound nicer than 64 bit (as it is sometimes the case with the low quality switch).
If you need every percent of your CPU’s power, then you can switch to 32 bit. If you are using more than one instance of the ArtsAcoustic Reverb, first switch down the less important ones.

The original reason, why we left the 32 bit mode is, when you open older projects. We know how annoying it can be to open a song after a few months and suddenly the CPU is to weak to play it because of a few little CPU percents. With the new ArtsAcoustic Reverb release 1.1, you even can be happy, because your recent projects will need less CPU, as the actual 32 bit mode needs less CPU power than before!


Ok, that’s it for the moment, let’s turn back to music and enjoy! :)
kind regards, timo
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KVRian
1119 posts since 29 Jun, 2004 from within you without you

Post Sat Nov 26, 2005 5:21 pm

imho the 64 bit mode is sublime! It sounds more spacious and beautiful. Like you mentioned, there is more profound depth of field. Sounds especially sweet in Sonar 5's 64 bit mix environment.

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