RE: [SLUG] Audio storage and manipulation

From: Ken Elliott (kelliott11@cfl.rr.com)
Date: Tue Jan 09 2007 - 20:54:32 EST


>> OK... What is thermal calc, I assume that it has to do with temperature.

Yes. Ever so often, a drive will stop accepting I/O commands in order to
recalculate the position of the head, relative to the platter. As the
platter and actuator arms warm up, they expand and that throws off the
position. In most applications, this is unnoticed. But in a real-time
application, you lose the data while this is going on. The general method
was to put a larger buffer on the drive and continue to accept I/O commands
while T-Calc was being performed. There are other methods, but you get the
idea.

>> Also what is a AV rated drive, is that AV as in Audio Visual?

Yes. All it means is that it will meet it's rated write speed continuously,
and that the write speed is fast enough for an audio/visual recording
application. One trick is to get a large drive, and partition is into
several small drives (or perhaps just one). Since the average access time
is calculated at the time it takes to move the heads from the centre of
partition to the edge of the partition, a smaller partition will speed up
seek time. On 'famous' drive is actually a large drive with the firmware
set to restrict the movement of the head to a small area.

One thing to watch for. Really large drives (consumer-grade) are now so
dense that they _always_ using error correction. If you want a robust
drive, get the smallest capacity drive you can get. The exception _might_
be high-end commercial SCSI drives, that are 3x as expensive and are far
more robust. My workstation has three 70GB 15,000 rpm drives hooked to an
Ultra 320 SCSI interface and they scoot!

Ken Elliott

=====================
-----Original Message-----
From: slug@nks.net [mailto:slug@nks.net] On Behalf Of Chuck Hast
Sent: Monday, January 08, 2007 3:22 AM
To: slug@nks.net
Subject: Re: [SLUG] Audio storage and manipulation

On 1/7/07, Ken Elliott <kelliott11@cfl.rr.com> wrote:
> >> Also need to be able to record to disk from mics etc
>
> For Recording:
> http://audacity.sourceforge.net/
>
Looks good, looks like it allows for all kinds of recording and audio mani-
pulation.

> This is the choice for a lot of podcasters. Since you already have a
> mixing board, you should be set. You may want to use a dedicated HDD
> for this application. Sometimes you can have dropouts due to thermal
> calc on the HDD, and when some other application (or the OS) fights
> for attention. A dedicated hard disc drive solves this issue. I
> prefer to use AV-rated drives, so t-calc is never an issue.
>
I figured I would need a dedicated HD for this only, have one that the OS
and apps live on and one that only handles audio files.

OK... What is thermal calc, I assume that it has to do with temperature.
Also what is a AV rated drive, is that AV as in Audio Visual? This is a new
area for me, but one that maybe I can help in, and get linux going in one
more location.

> Look at some of the podcaster apps. They are designed to cue up music
> and sound clips to be fired off easily (radio DJ-style). And that
> sounds like what you are trying to do.
>

I will look and see what is available for Linux...

--
Chuck Hast  -- KP4DJT --
To paraphrase my flight instructor;
"the only dumb question is the one you DID NOT ask resulting in my going out
and having to identify your bits and pieces in the midst of torn and twisted
metal."
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