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wrc1944
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PostPosted: Sat Aug 04, 2012 1:04 am    Post subject: KLANG: A New Linux Audio System For The Kernel Reply with quote

Just ran across this item.

KLANG: A New Linux Audio System For The Kernel

Anyone have more info or thoughts on this, and is it something to look forward to?

As one who's sought a really great Linux pro audio solution for a long time now, It sure sounds intriguing to me.

http://www.phoronix.com/scan.php?page=news_item&px=MTE1MDc

http://klang.eudyptula.org/
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PaulBredbury
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PostPosted: Sat Aug 04, 2012 1:21 pm    Post subject: Reply with quote

Interesting discussion.

Until I can patch it into the kernel and play with it, I shall remain a reluctant ALSA fanboi.
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Ant P.
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PostPosted: Sat Aug 04, 2012 3:44 pm    Post subject: Reply with quote

Knee-jerk reaction
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John R. Graham
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PostPosted: Tue Aug 07, 2012 7:10 pm    Post subject: Reply with quote

Moved from Multimedia to Unsupported Software. Not in Portage so it fits better here.

- John
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PostPosted: Thu Aug 09, 2012 3:43 pm    Post subject: Reply with quote

I followed some bits of the discussion between KLANG guy and Lennart Poettering at Linux Expo. I wouldn't pay much attention to it as it looks like the guy behind it (Wolfgang Draxinger) doesn't really have thorough understanding of real-time sound and Linux internals, as pointed to by Paul Davis (JACK developer) on the dedicated Phoronix discussion.
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krinn
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PostPosted: Thu Aug 09, 2012 5:39 pm    Post subject: Reply with quote

Great discoveries were made by mistakes and hazard.

So, even if he fail, that guy might do something everyone with high understanding of sound and real-time linux will never do because it appears silly for them, and maybe discover something that is finally useful and a great step for them.
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VinzC
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PostPosted: Thu Aug 09, 2012 7:03 pm    Post subject: Reply with quote

krinn wrote:
Great discoveries were made by mistakes and hazard.

So, even if he fail, that guy might do something everyone with high understanding of sound and real-time linux will never do because it appears silly for them, and maybe discover something that is finally useful and a great step for them.

Maybe. But the major argument I retain is about using floating point for audio. It is currently used in major audio software and wanting to port that to kernel is the reason why it's a blocker: floating point in the (Linux) kernel is prohibited. So as far as I can see it, KLANG is likely not going to happen otherwise at least one of its goals (precision and/or speed for integer instruction uses more clocks than SSE, for instance) is going to fail.
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PostPosted: Tue Aug 21, 2012 3:36 pm    Post subject: Reply with quote

Plz no more audio engines for linux.Rather improve the existing ones.
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PostPosted: Tue Aug 21, 2012 4:12 pm    Post subject: Reply with quote

VinzC wrote:
the major argument I retain is about using floating point for audio. It is currently used in major audio software and wanting to port that to kernel is the reason why it's a blocker: floating point in the (Linux) kernel is prohibited. So as far as I can see it, KLANG is likely not going to happen otherwise at least one of its goals (precision and/or speed for integer instruction uses more clocks than SSE, for instance) is going to fail.

He might not be the kernel expert, but on phoronix he made the point:
floating point is about large scales at the price of precision. You may want to mesure big stars and bacteria on a common scale, but did you once hear any sound above 30 thousand Hertz?
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PostPosted: Wed Aug 22, 2012 8:27 am    Post subject: Reply with quote

VinzC wrote:
the major argument I retain is about using floating point for audio. It is currently used in major audio software and wanting to port that to kernel is the reason why it's a blocker: floating point in the (Linux) kernel is prohibited. So as far as I can see it, KLANG is likely not going to happen otherwise at least one of its goals (precision and/or speed for integer instruction uses more clocks than SSE, for instance) is going to fail.

ulenrich wrote:
He might not be the kernel expert, but on phoronix he made the point:
floating point is about large scales at the price of precision. You may want to mesure big stars and bacteria on a common scale, but did you once hear any sound above 30 thousand Hertz?

That's wrong, really: floating points are not meant for large scales but also for small numbers, between 0 and 1, for instance, which might result from signal processing (although I don't really know the internals of a DSP); floats do quite make sense. The point in using floats is that the precision (e.g. the number of significant digits or the mantissa) is constant. With integer numbers that precision decreases when the number is small, potentially leading to more noise with small values. But even then, most audio processing software are said to use floats. Also floating point operations are faster than integer operations so it makes no sense to use integers in the process.
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PostPosted: Wed Aug 22, 2012 10:31 am    Post subject: Reply with quote

Why are floats not allowed in kernel code?
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PostPosted: Wed Aug 22, 2012 10:43 am    Post subject: Reply with quote

Hello,

Do the audio hardware support floating point buffers ? I don't think so.
So, there is at least two layers :
- the hardware support, with integer buffer
- the audio engine, as an application, which communicate with the kernel, and converting the floating point streams.
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PostPosted: Wed Aug 22, 2012 12:07 pm    Post subject: Reply with quote

VinzC wrote:
Also floating point operations are faster than integer operations

Not necessarily:

http://www.keil.com/support/docs/1476.htm

http://stackoverflow.com/questions/2550281/floating-point-vs-integer-calculations-on-modern-hardware
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PaulBredbury
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PostPosted: Wed Aug 22, 2012 3:28 pm    Post subject: Reply with quote

Herring42 wrote:
Why are floats not allowed in kernel code?

They are allowed when justifiable, but it's complicated - has different subtleties, and potential slowness of switching in and out of floating-point mode, depending on the architecture.

Code:
$ find /usr/src/linux-3.4.9/ -name \*.c | xargs grep kernel_fpu_begin\( | wc -l
35
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Ant P.
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PostPosted: Wed Aug 22, 2012 5:27 pm    Post subject: Reply with quote

I don't see why people are up in arms about this using fixed-point because it's in-kernel. How do you think ALSA already does it?
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PostPosted: Thu Aug 23, 2012 7:00 am    Post subject: Reply with quote

VinzC wrote:
Also floating point operations are faster than integer operations

Fitzcarraldo wrote:
Not necessarily:

http://www.keil.com/support/docs/1476.htm

http://stackoverflow.com/questions/2550281/floating-point-vs-integer-calculations-on-modern-hardware

My bad: I only checked the clock cycles of a few opcodes on Intel CPU. Might indeed not be the same on *every* supported architecture.
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