Re: [Jack-Devel] low latency . what does it mean? how is it achieved?

Hi Paul,
thank you for the information!
While these are all valid points, in the case of music composition entirely
on a pc (with sequencers / sound generators / and digital fx all working as
programs) capturing noise really comes 2nd. And the plethora of output
audio buses that are available on the ac97 make it rather good deal.

I don't see you saying anywhere that I cannot run the ac97 with a small
buffer size, though! :)
So If I use a preemptive kernel in linux (such as the one that is found in
ubuntu studio) and set the buffer size to something in the order of 64/128
samples , it should work flawlessly ??

any book that you may have read... or written :) would also be a very
explanatory read...

Thanks!



On Wed, Apr 16, 2014 at 10:14 AM, Paul Davis <[hidden]>wrote:

>
>
>
> On Wed, Apr 16, 2014 at 2:48 AM, Athanasios Silis <
> [hidden]> wrote:
>
>> Hi all,
>> I find myself wondering again and again what makes a difference between a
>> simple AC '97 audio chip and a professional sound card...
>>
>> I mean the chips are different, sure, but I always hear about
>> "professional equipement, does not go through the normal application
>> execution path", or something in those lines.
>>
>
> marketing BS from the old windows days when the only "normal" path for
> sound added 100ms. this has not been true for a long time on windows, and
> has never been relevant on linux.
>
>
>>
>> both ac97 and professional chips go through ALSA (in linux at least).
>> what gives an edge to the professional chip then? Why can I not run an ac97
>> with a latency of 10msec or so (and a low latency kernel) ? I mean, the
>> processing power of a core i7 should be enough to run audio, right?
>>
>
> latency rarely has anything to do with processing power. latency is about
> the ability to meet deadlines. it is not dependent on processing power
> (typically) but rather on the lack of operations that take a long time and
> prevent sufficiently "on-time" processing of audio data.
>
> the key features of "pro" audio interfaces are typically:
>
>     * playback and capture streams run from the same sample clock and are
> thus always synchronized
>     * often have analog connections outside the radio-frequency-noisy
> environment of the computer chassis
>     * have the option to use an external sample clock, enabling correct
> integration with multiple devices
>     * lack of onboard DSP (though this varies by manufacturer)
>     * ability to handle different sample rates in the hardware without
> relying on resampling by the operating system device driver
>
> the ac97 chipset itself isn't particularly bad, but it is typically
> mounted on the motherboard along with analog connection points. doing
> analog->digital and digital->analog conversions in this environment is not
> ideal. in addition, the ac97 chipset and specification has a lot of stuff
> associated with consumer/home "theater" requirements that are not of
> interest for use in pro-audio or music creation scenarios.
>

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