Is it just a file structure thing so it only occurs when multiple
files are combined for access on (eg) CD, or is each file inherently a
different size?

Karl Engel wrote:

Is it just a file structure thing so it only occurs when multiple
files are combined for access on (eg) CD, or is each file inherently a
different size?

There is a ton of error detection/error correction data that is added when
the data is recorded on every audio CD. There's even more error
detection/error correction data that is added to CDROMs. This is one reason
why the CD ROM format is preferred for archiving audio data.

The CD burning software adds error detection/error correction data
more-or-less transparently, right before the data it sent to the CD Burner.

The CD player/reader hardware removeserror detection/error correction data
before forwarding the data to audio section of the CD player, or the
software running on the PC.

Just out of curiosity, would you happen to know the ratio of [correction
bits : actual data bits] typically used on CD audio?

Dave

"Arny Krueger" wrote in message
...
Karl Engel wrote:

Is it just a file structure thing so it only occurs when multiple
files are combined for access on (eg) CD, or is each file inherently a
different size?

There is a ton of error detection/error correction data that is added when
the data is recorded on every audio CD. There's even more error
detection/error correction data that is added to CDROMs. This is one
reason
why the CD ROM format is preferred for archiving audio data.

The CD burning software adds error detection/error correction data
more-or-less transparently, right before the data it sent to the CD
Burner.

The CD player/reader hardware removeserror detection/error correction data
before forwarding the data to audio section of the CD player, or the
software running on the PC.

Doesn't the material on audio CDs are compressed with a ratio of 1:1,5?

bence

"Arny Krueger" wrote in message
...
Karl Engel wrote:

Is it just a file structure thing so it only occurs when multiple
files are combined for access on (eg) CD, or is each file inherently a
different size?

There is a ton of error detection/error correction data that is added when
the data is recorded on every audio CD. There's even more error
detection/error correction data that is added to CDROMs. This is one
reason
why the CD ROM format is preferred for archiving audio data.

The CD burning software adds error detection/error correction data
more-or-less transparently, right before the data it sent to the CD
Burner.

The CD player/reader hardware removeserror detection/error correction data
before forwarding the data to audio section of the CD player, or the
software running on the PC.

Doesn't the material on audio CDs are compressed
with a ratio of 1:1,5?

Actually, the data on an audio CD are "expanded" by a factor of 14:8. This is
called "eight to fourteen modulation" (EFM). Each byte is mapped to 14 bits,
which makes the data much more robust.

Locsmándi Bence wrote:
Doesn't the material on audio CDs are compressed with a ratio of 1:1,5?

No.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"Karl Engel" wrote in message
om...
Is it just a file structure thing so it only occurs when multiple
files are combined for access on (eg) CD, or is each file inherently a
different size?

..CDA files are simply headers, not music. You don't get to see the
corresponding raw PCM data on a pressed/burned CDDA. Don't know about Macs,
but at least not with any PC I've built.

Now I don't know if that's what you meant, but it's the question you asked.

--
-----------

Roger W. Norman
SirMusic Studio

"Karl Engel" wrote in message
om...
Is it just a file structure thing so it only occurs when multiple
files are combined for access on (eg) CD, or is each file inherently a
different size?

..cda files are only pointers.

On Thu, 1 Apr 2004 08:53:42 -0500, "David Grant"
wrote:

Just out of curiosity, would you happen to know the ratio of [correction
bits : actual data bits] typically used on CD audio?

64 parity bits are added for each 192 data bits, along with 27 sync
and 8 subcode bits. These "frames" are interleaved and then run
through an eight to fourteen lookup table to minimize long
strings of 1's or 0's.

For a complete and interesting explanation, try Ken Pohlmann's
books, especially "Principles of Digital Audio".

Chris Hornbeck

"David Grant" wrote in message m...
Just out of curiosity, would you happen to know the ratio of [correction
bits : actual data bits] typically used on CD audio?

1:3

See

http://www.ee.washington.edu/consele...udio2/95x7.htm

for details.

Sam

Roger W. Norman wrote:

"Karl Engel" wrote in message
om...
Is it just a file structure thing so it only occurs when multiple
files are combined for access on (eg) CD, or is each file inherently a
different size?

.CDA files are simply headers, not music. You don't get to see the
corresponding raw PCM data on a pressed/burned CDDA. Don't know about Macs,
but at least not with any PC I've built.

Now I don't know if that's what you meant, but it's the question you asked.


I think what he really wanted to know is why you can record 74 minutes
of audio on a 650MB CD-R, but 74 minutes of audio data takes up more
than 650MB of disk space on a data-format CD-ROM or on a hard drive.

ulysses

Justin Ulysses Morse wrote:
Roger W. Norman wrote:


"Karl Engel" wrote in message
.com...

Is it just a file structure thing so it only occurs when multiple
files are combined for access on (eg) CD, or is each file inherently a
different size?

.CDA files are simply headers, not music. You don't get to see the
corresponding raw PCM data on a pressed/burned CDDA. Don't know about Macs,
but at least not with any PC I've built.

Now I don't know if that's what you meant, but it's the question you asked.



I think what he really wanted to know is why you can record 74 minutes
of audio on a 650MB CD-R, but 74 minutes of audio data takes up more
than 650MB of disk space on a data-format CD-ROM or on a hard drive.

ISTR that the directory on a CD-R takes 32 MB for the first session and 16 MB
after that, so there's a sizeable chunk you never see. Audio CDs don't have that.

"Justin Ulysses Morse" wrote ...
I think what he really wanted to know is why you can record 74 minutes
of audio on a 650MB CD-R, but 74 minutes of audio data takes up more
than 650MB of disk space on a data-format CD-ROM or on a hard drive.

Because the CD-ROM data format uses significantly more error
detection/correction overhead than the Red Book audio format uses.