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Re: How to slow down noisy CDROM
- To: Schlomo Schapiro <schlomo(at-nospam)schapiro.org>
- Subject: Re: How to slow down noisy CDROM
- From: "Nadav Har'El" <nyh(at-nospam)math.technion.ac.il>
- Date: Fri, 1 Dec 2000 19:12:00 +0200
- Hebrew-Date: 5 Kislev 5761
- In-Reply-To: <Pine.LNX.4.21_heb2.08.0012011534001.411-100000@nessy.home>; from schlomo@schapiro.org on Fri, Dec 01, 2000 at 03:37:45PM +0200
- References: <Pine.LNX.4.21_heb2.08.0012011534001.411-100000@nessy.home>
- Resent-Date: Fri, 1 Dec 2000 19:28:48 +0200
- Resent-From: nyh(at-nospam)math.technion.ac.il
- Resent-Message-Id: <200012011728.TAA00750@leeor.math.technion.ac.il>
- Resent-To: linux-il(at-nospam)cs.huji.ac.il
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On Fri, Dec 01, 2000, Schlomo Schapiro wrote about "How to slow down noisy CDROM":
> Hi,
>
> does anybody know how to slow down a noisy CD ? I use it mostly to play
> MP3s and the vacuum cleaner noise doesn't fit the music (and the CD would
> be still fast enough if it would run at 4x instead of 36x).
Another solution is to cache the music: if your CD player can read at 20x
speed (I don't believe the manufacturer's data to represent anything of
relevance to the truth ;)), then you can read 15 minutes of music in 5
seconds (quick calculation: mp3 is about 10 times smaller than raw CD data,
20x makes you able to read data 200 times faster than it will play later).
So you can write a small script which, every 15 minutes, reads the next
15 minutes of music from the CD onto the hard disk. It will only be 5
seconds of noise every 15 minutes (even if it's 10 seconds, it's not too
bad - if the drive needs to seek (the music is not contiguous) it will take
somewhat longer, but still not too bad). If you want you can do other
varients on this idea: e.g., if you have 100MB free space on your harddrive
you can read 100 minutes of music from the CD (this will take 30-60 seconds,
I think), once every 100 minutes. Given enough disk-space you can even copy
the entire CD (650MB) to the hard-disk and play the music from there.
By the way, there's a commercial mp3 player that takes this approach for
somewhat different purpose: that player has a 10 GB hard disk to store
*tons* of music, random access and rewritable. However because it is a
portable player, the hard disk is problematic if it spins continuously -
it wastes a lot of energy and it can be damaged by too-violent motions.
So what they do is have a memory cache of, say, 4MB that holds 4 minutes
of music. The drive has to be spun up once every 4 minutes, the 4MB of
data is read in a couple of seconds, and the drive is spun down. The
player can (in theory - I don't remember the implentation details) choose
an appropriate time to read from the hard-disk using motion sensors, and
if a read fails it can retry a while later - while still playing what it
has left in the 4-minute buffer.
--
Nadav Har'El | Friday, Dec 1 2000, 5 Kislev 5761
nyh@math.technion.ac.il |-----------------------------------------
Phone: +972-53-245868, ICQ 13349191 |Cigarette: tobacco wrapped in paper,
http://nadav.harel.org.il |fire at one end, and a fool at the other.
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