<div><div class="gmail_quote">On Mon, May 17, 2010 at 9:49 AM, Fernando Lopez-Lezcano <span dir="ltr"><<a href="mailto:nando@ccrma.stanford.edu">nando@ccrma.stanford.edu</a>></span> wrote:<blockquote class="gmail_quote" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0.8ex; border-left-width: 1px; border-left-color: rgb(204, 204, 204); border-left-style: solid; padding-left: 1ex; ">
<a href="http://ccrma-mail.stanford.edu/pipermail/planetccrma/2010-March/016513.html" target="_blank">http://ccrma-mail.stanford.edu/pipermail/planetccrma/2010-March/016513.html</a><br><div class="im">...</div></blockquote>
<blockquote class="gmail_quote" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0.8ex; border-left-width: 1px; border-left-color: rgb(204, 204, 204); border-left-style: solid; padding-left: 1ex; ">
The HPET or other clock sources that are used for timing in the kernel<br>are _not_ physically connected (to my knowledge) to the clock source<br>that ships the samples through the sound card. That is a separate clock,<br>
either a crystal in the sound card hardware itself or a clock signal<br>derived from the master crystal that drives the cpu clock. It does not<br>go through the kernel, it is a hardware feature. The kernel will<br>(should?) not affect where and how the hardware (a/d:d/a) gets the clock<br>
from.</blockquote></div></div><div><br></div><div>I agree. Thanks for clarifying this (again).</div><div><br></div><div>However, note <a href="http://linux.die.net/man/1/jackd">http://linux.die.net/man/1/jackd</a></div><div>
<br></div><div><a href="http://linux.die.net/man/1/jackd"></a><blockquote class="gmail_quote" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0.8ex; border-left-width: 1px; border-left-color: rgb(204, 204, 204); border-left-style: solid; padding-left: 1ex; ">
-c, --clocksource ( c(ycle) | h(pet) | s(ystem) )</blockquote><blockquote class="gmail_quote" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0.8ex; border-left-width: 1px; border-left-color: rgb(204, 204, 204); border-left-style: solid; padding-left: 1ex; ">
Select a specific wall clock (Cycle Counter, HPET timer, System timer).</blockquote><div><br></div><div>If you're telling jackd to run at a certain sample rate, e.g. 48k, how is it going to know what 48k actually is? Via the clock. </div>
<div><br></div><div><a href="https://wiki.archlinux.org/index.php/User_talk:Hollunder#timers.2C_hpet.2C_hrtimer">https://wiki.archlinux.org/index.php/User_talk:Hollunder#timers.2C_hpet.2C_hrtimer</a> indicates the main improvement w/ using HPET in jack is better midi timing.</div>
<div><br></div><div><a href="http://www.mail-archive.com/proaudio@lists.tuxfamily.org/msg03199.html">http://www.mail-archive.com/proaudio@lists.tuxfamily.org/msg03199.html</a> also suggests the soundcard crystal oscillator is ultimately in control of the sample rate, and mentions the only time-related issue is the buffer running dry. Which could happen if there's a difference between what the soundcard thinks as 48k and what the system thinks of as 48k.</div>
<div><br></div><div>So If your clock isn't sampling often enough, or accurate-enough, couldn't that affect the sound? Although in jack, i guess you'd see that as a buffer overrun, and increase your buffers to fix it. Perhaps using a desktop audio system and a media player, you wouldn't get such indication. But then again pa and dmix in alsa use large buffers to begin with...</div>
<div><br></div><div>One last idea why a system update might improve the sound. Less resampling? For example if you formerly accessed through alsa dmix at a 48k rate for compatibility w/ legacy AC-97; now f13 supports native 44.1 and many other rates, and you can listen to your music at it's original 44.1K sample rate? Perhaps an improved pulseaudio-> ALSA configuration that just invokes "plug" to align the sample to whatever is required by the hardware, but not use "dmix" to resample?</div>
<div><br></div><div>I hope to be freeing up a machine for f13 in the next months so I guess I'll find out more about F13's ALSA configuration. I might even leave pulseaudio running</div><div>for a bit just to see how things work for everybody else :-).</div>
<div><br></div>Niels<br><a href="http://nielsmayer.com">http://nielsmayer.com</a><br></div>