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View Full Version : reasonable expectations for ripping speed



pfarrell
2009-11-06, 22:39
In a discussion on the main list, one regular thought that taking four
minutes to rip (actually just extract) music from a CD is way too long.

> But seriously: that's the old priorities issue.
> Would it be possible to just _rip_ the CD first (rip a 1:1 copy as an
> image to hd) and the use that for the CDPlayer plugin while the
> autoripper continues to encode the original CD? Or copy the iso and do
> both from HD in parallel or something...

Back when people actually bought CD drives for PCs (most modern ones are
at least DVD drives and many are BlueRay), the CD drive vendors competed
on speed. They could claim that their new drive was 5X, meaning five
times faster than reading a disk at normal CD speed. Then the next
vendor would say "That is slow, my new drive is 8X"

The first question is "what is the base X that starts all this?"

The CD audio spec (aka RedBook) was designed to hold about 70 minutes of
music. (perhaps 74 minutes). The CD was not invented for computer data,
it was to replace the hated (by the record companies) cassette tape.

Data Rate = "X"
= 16 bits * 2 channels * 44.1kHz
= 16 * 2 * 44100
= 1,411,200 bits/second
= 176,400 bytes/second
= 172 Kbytes/second

So it is easy to see that to make CD audio, you need at about 1.5
Megabits per second. This is "X", 172KB per second. This also means that
if you want to stream RedBook audio, you need to pass about 1.5 Mbs.

To claim that a drive is 10X, it has to be able to read a whole CD in
under eight minutes. 20X under four minutes.

In practice, the ratings were marketing hope, at best what could be seen
in a lab under optimal conditions. So take the ratings with a large
grain of salt.

But to address the fundamental question: why can't you rip a CD in
seconds? the answer is that with a 70X drive, you could do it in about
one minute. Of course, then you get to compress it, tag it, etc.

Most pop/rock/country/etc CDs are not full, so you can do it faster. But
a couple of minutes is a reasonable lower bound.

--
Pat Farrell
http://www.pfarrell.com/

funkstar
2009-11-07, 03:22
In practice, the ratings were marketing hope, at best what could be seen
in a lab under optimal conditions. So take the ratings with a large
grain of salt.
I forget what speed CAV (Constant Angular Velocity) and CLV (Constant Linear Velocity) started to be thrown about by CD-ROm manufacturers, but i think it was at about 12x and over. The top transfer rates were only for the outer most section of the disk as it was travelling fastest. Drives usually have "24x Max" or something similar to indicate that you would only get that kind of speeds in certain circumstances.

Add to that those speeds were only ever for reading data, not for ripping audio, these are very different functions for an optical drive. Video data on a DVD, HD-DVD or BluRay are just files on a data disk. Audio on a CD is completely different, this is why you have to rip it as opposed to just copying some files off the disk. Ripping at high speed is a lot harder for a drive to do, the Audio-CD was never designed to make this easy, it was just designed to play 16/44.1 PCM audio. Anything else you can do with an actual CD has been tacked on well after audio CDs were released.

maggior
2009-11-07, 09:02
TDK at one point marketed their CD-R drives based on their audio ripping speed and qualitities. I used one for a while - it has a fabulous (at the time) burning speed of 12x. It ripped at a pretty good rate.

The best rip rate I've seen is my Plextor Premium. On the outer edges of a disc, it will approach 40x.

pfarrell
2009-11-07, 09:07
maggior wrote:
> The best rip rate I've seen is my Plextor Premium. On the outer edges
> of a disc, it will approach 40x.

Nearly a decade ago, we tested real world ripping speeds and I got one
of the winners, it was a TDK drive. I don't think it was as fast as your
40x, but it was fast.

Your 40x will still take two minutes for a full audio disk. Plus
compression, normalizing, etc.

--
Pat Farrell
http://www.pfarrell.com/