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Guest
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 Posted:
Mon Oct 10, 2005 3:10 pm Post subject:
74 min. at 16x44.1 is 747MB. How does it fit on a 650 MB dis |
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Hi. I'm thinking of buying a portable CF media recorder that can record
at various bit depths/sample rates. Whilst researching which CF card I
would want to go with the recorder, it dawned on me that the 74
minute/650 MB capacity CD disc paradigm just doesn't calculate:
(((((16 x 44100) / 1,048,576) / 8) x 60) x 2) x 74 = 746.93
16 bits/sample x 44,100 samples/second = 705,600 bits/s
divide by 1,048,576 bits per megabit = .673 Megabits/s
divide by 8 bits per byte = .084 MB/s
times 60 s/min = 5.05 MB/min per audio channel
times 2 channels for stereo = 10.1 MB/min
times 74 min = 746.93 MB
I churned through the CD-R FAQ ( http://www.cdrfaq.org/faq.html )
pretty thoroughly and didn't see this addressed. Still could have
missed it though. Can anyone explain or point me at info about this
discrepancy? Is the raw PCM information somehow (gasp!) _compressed_ on
CD? Or is a CD actually bigger than 650 MB? Or...? Thanks!
Peace,
Sanaka |
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Andrew Reid
Guest
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| Posted:
Mon Oct 10, 2005 7:25 pm Post subject:
Re: 74 min. at 16x44.1 is 747MB. How does it fit on a 650 MB |
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On 10 Oct 2005 03:10:29 -0700, sanaka@gmail.com wrote:
| Quote: | Hi. I'm thinking of buying a portable CF media recorder that can record
at various bit depths/sample rates. Whilst researching which CF card I
would want to go with the recorder, it dawned on me that the 74
minute/650 MB capacity CD disc paradigm just doesn't calculate:
(((((16 x 44100) / 1,048,576) / 8) x 60) x 2) x 74 = 746.93
16 bits/sample x 44,100 samples/second = 705,600 bits/s
divide by 1,048,576 bits per megabit = .673 Megabits/s
divide by 8 bits per byte = .084 MB/s
times 60 s/min = 5.05 MB/min per audio channel
times 2 channels for stereo = 10.1 MB/min
times 74 min = 746.93 MB
I churned through the CD-R FAQ ( http://www.cdrfaq.org/faq.html )
pretty thoroughly and didn't see this addressed. Still could have
missed it though. Can anyone explain or point me at info about this
discrepancy? Is the raw PCM information somehow (gasp!) _compressed_ on
CD? Or is a CD actually bigger than 650 MB? Or...? Thanks!
Peace,
Sanaka
|
The figure 74min/650MB is actually two completely different things
The 650-700MB spec is for 'Data Disks'. CD data disks have error
correction bits that chew up quite a bit of the storage area of a CD.
In other words you can get 650-700MB of data on a CD and the rest of
the CD's space is taken up by the error correction bits.
Audio 'data' contains no error correction bits so ALL of the CD can be
used for the audio information.
I hope that's clear as I haven't had my morning coffee yet :-)
--
Reply to:
Reido
reido741@hotmail.com |
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Spamless
Guest
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| Posted:
Mon Oct 10, 2005 7:49 pm Post subject:
Re: 74 min. at 16x44.1 is 747MB. How does it fit on a 650 MB |
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On 2005-10-10, sanaka@gmail.com <sanaka@gmail.com> wrote:
| Quote: | Hi. I'm thinking of buying a portable CF media recorder that can record
at various bit depths/sample rates. Whilst researching which CF card I
would want to go with the recorder, it dawned on me that the 74
minute/650 MB capacity CD disc paradigm just doesn't calculate:
(((((16 x 44100) / 1,048,576) / 8) x 60) x 2) x 74 = 746.93
16 bits/sample x 44,100 samples/second = 705,600 bits/s
divide by 1,048,576 bits per megabit = .673 Megabits/s
divide by 8 bits per byte = .084 MB/s
times 60 s/min = 5.05 MB/min per audio channel
times 2 channels for stereo = 10.1 MB/min
times 74 min = 746.93 MB
I churned through the CD-R FAQ ( http://www.cdrfaq.org/faq.html )
pretty thoroughly and didn't see this addressed. Still could have
missed it though. Can anyone explain or point me at info about this
discrepancy? Is the raw PCM information somehow (gasp!) _compressed_ on
CD? Or is a CD actually bigger than 650 MB? Or...? Thanks!
|
CD's can have data on them in different formats. Extra data, such as
checksums, depend on the format. Those checksums take up space and the
different formats have different number of data bytes which can be stored in
each sector. Each sector contains data, for an audio CD, for 1/75 second.
At 44,100 samples/second * 2 channels/sample * 2 bytes/channel * 1/75 second
gives 2352 bytes of audio data per sector. There are also some bytes which
(unless you use a RAW mode) you will not be able to write (the "subchannel"
data used by the reader - e.g. cdrecord, open software burner, if one's
burner supports it, can write in -raw96r mode:
Select Set RAW writing mode with 2352 byte sectors plus 96 bytes of
raw P-W subchannel data resulting in a sector size of 2448 bytes.
CD-DA (similar to Red Book) audio format: 2352 bytes per sector [audio CD]
CD-ROM mode 1 (Yellow Book) format: 2048 bytes per sector [data CD]
(there are other formats)
a (nominal) 74 minute CD contains: 74minutes * 60 seconds/minute * 75 sectors/second
333,000 sectors, which at 2352 bytes per sector is 783,216,000 bytes
or 783 Meg (decimal) or 747 Meg (binary) (1 Meg decimal = 1,000,000 = 1000*1000,
1 Meg binary = 1,048,576 = 1024 * 1024 while a floppy disk, at 1.44 Meg,
uses a mixed "Meg" - it's Meg is 1 Meg mixed = 1024*1000!)
That same disk with those same sectors can only hold 2048 bytes as a data CD
(but with better error correcting codes, etc. - codes which take up some of
the space in the sector) and so, at 2048 bytes/sector * 333000 sectors it
holds 681,984,000 bytes = 681 Meg (decimal) = 650 Meg (binary)
So, as a data disk it can hold 650 Meg (binary) or 74 minutes of audio data
(747 Meg binary).
If you record a WAV file to media, it records as a data file - the data file
will take 747 Meg binary for 74 minutes. You cannot rip the audio from an
audio CD which has 74 minutes of music (747 Meg binary) and then save the
music to a (standar) 74 min/650 Meg CD as wav files (that would save it as
data and the disk only holds 650 Meg binary as a data disk). |
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Mike Richter
Guest
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| Posted:
Mon Oct 10, 2005 10:30 pm Post subject:
Re: 74 min. at 16x44.1 is 747MB. How does it fit on a 650 MB |
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Andrew Reid wrote:
| Quote: | The figure 74min/650MB is actually two completely different things
The 650-700MB spec is for 'Data Disks'. CD data disks have error
correction bits that chew up quite a bit of the storage area of a CD.
In other words you can get 650-700MB of data on a CD and the rest of
the CD's space is taken up by the error correction bits.
Audio 'data' contains no error correction bits so ALL of the CD can be
used for the audio information.
|
You're in good shape until that last. There is substantial error
correction on any CD format; if there were not, data would be impossible
to retrieve given the high inherent error rate. However, there is one
extra layer on a data disc - hence the reduced capacity - which is not
on an audio disc.
There's a page on the encoding of information on a CD in the primer at
my WWW site; it may help understanding.
Mike
--
mrichter@cpl.net
http://www.mrichter.com/ |
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Guest
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| Posted:
Mon Oct 10, 2005 11:58 pm Post subject:
Re: 74 min. at 16x44.1 is 747MB. How does it fit on a 650 MB |
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Awesome. Thanks, folks. That helps alot, as I wish to record with a
device which will create .wav's as regular data files, but with the
ultimate intent of the audio going to CD.
Also, this _is_ in the CDR FAQ, in a whole section I didn't discover
'til later, but not in so much detail as your responses above.
So I guess a rule of thumb would be to use minutes, not MB or MiB, to
estimate CD capacity usage. I.e.: on hard drive, divide (16x44.1) wav
file MB size by 10.1 to get minutes of audio. Then check against your
CDR also in minutes (like 74 or 80), not MB or MiB.
Peace,
Sanaka |
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smh
Guest
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| Posted:
Tue Oct 11, 2005 1:33 am Post subject:
Mike Richter's Cockamamie Mumbo Jumbo on C1/C2 Errors |
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.. --------------------------------------
Mike Richter, were you born with
"Scam Artist" emblazoned on your face?
--------------------------------------
http://tinyurl.com/6eldj
(No Mikey S-lickers have been able to prove ANY of the above is a LIBEL)
( )
( -- despite Mikey claimed to have proof of misquotes !! )
'
Mike Richter (Slimy Friggin Shit) splattered:
| Quote: |
There is substantial error
correction on any CD format; if there were not, data would be impossible
to retrieve given the high inherent error rate.
|
Expert on the error rate, Mikey?
-----------------------------------------------------
Mike Richter's Cockamamie Mumbo Jumbo on C1/C2 Errors
-----------------------------------------------------
=============================================
From: Noik
Date: 8/13/05
Mike Richter (Slimy Friggin Shit) splattered:
| Quote: |
James Perrett wrote:
if I'm seeing C2 errors then there MUST, by definition,
be C1 errors on the disc - in fact, every disc will
have a few C1 errors.
You are assuming a correlation between C1 and C2 errors
which is stronger than reality.
They are different measures and while they do have a gross
correlation, it is not the sort you are expecting.
I still feel that C1 and C2 errors are substantially different.
|
I think that a C2 error is a C1 error(s) that couldn't be corrected
with the C1 error correction capabilities. They're not independant,
they're basically the same thing except for which level of error
correction can correct the error. You're using a program that just
doesn't report C1 errors, as indicated by the fact that the "C1 error"
part in your screenshot is greyed out.
Now I know why you can create disks that have no C1 errors.
=============================================
-------------------------------
Wow! What a slimy friggin SOB!
----------------------------------------
Mikey, you are the Slimiest Friggin SOB!
----------------------------------------
Mike Richter, were you born with
"Scam Artist" emblazoned on your face?
--------------------------------------
(Mike Richter, any Material Connection w/ Roxio?) |
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smh
Guest
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| Posted:
Tue Oct 11, 2005 5:55 am Post subject:
Mike Richter, Digging C1 Errors out of Assholes? (10-05) |
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.. --------------------------------------
Mike Richter, were you born with
"Scam Artist" emblazoned on your face?
--------------------------------------
http://tinyurl.com/6eldj
(No Mikey S-lickers have been able to prove ANY of the above is a LIBEL)
( )
( -- despite Mikey claimed to have proof of misquotes !! )
'
Mike Richter (Slimy Friggin Shit) splattered:
| Quote: |
There is substantial error
correction on any CD format; if there were not, data would be impossible
to retrieve given the high inherent error rate.
|
Mikey must have dug the C1 errors out of assholes:
------------------------------------------------
Mike Richter, Digging C1 Errors out of Assholes?
------------------------------------------------
Mike Richter (Slimy Friggin Shit) splattered (8/10/05):
| Quote: |
James Perrett wrote:
Do you ever see any C1 errors with CDSpeed on your machines?
I recall having seen C1 errors on earlier versions of CDSpeed,
but I have run tests on several faulty discs on a number of drives
and can find no C1 errors any longer.
Perhaps the program has changed;
perhaps my drives (Plextor and Pioneer) are to blame.
Unfortunately, I'm not running Plextools and therefore have no further
information to offer.
|
Perhaps the Plextor used to pull the C1 errors out of thin air?
Perhaps CDSpeed used to pull the C1 errors out of thin air?
Perhaps Plextools used to pull the C1 errors out of thin air?
Anyhow, how would you get the C1 errors when you don't even have
a drive reporting the C1 errors?
Perhaps you used to dig the C1 errors out of your assholes, Mikey?
'
-------------------------------
Wow! What a slimy friggin SOB!
----------------------------------------
Mikey, you are the Slimiest Friggin SOB!
----------------------------------------
Mike Richter, were you born with
"Scam Artist" emblazoned on your face?
--------------------------------------
(Mike Richter, any Material Connection w/ Roxio?) |
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