Burning a CD -- Minutes vs. File Size

[Opv]

When creating an audio CD using a standard 80 minute CD, is the amount of audio that can be recorded constrained exclusively by the number of minutes of audio to be burned, or does the size of the files come into play? (I'm speaking exclusively about burning an audio CD, not merely copying data files to the disk.)

For example, say I have two sets of audio files, both comprised of exactly 72 minutes of audio. However, one set of files is in WAV format hypothetically taking up 1,000 MB of disk space, while the second set of files are in MP3 format hypothetically taking up only 250 MB of disk space. When attempting to create an audio CD using these sets of audio files, are they equal in that they both equal 72 miniutes of audio or would the size of the WAV files be prohibitive, even though the total minutes of audio is within the CD capacity?

I guess what I'm asking is if one minute of audio is always equal to one minute of audio (once it's burned) when burning an audio CD?

[johns0]

80 minutes of audio burned as an audio cd will always be 80 minutes of play time.

[Opv]

I understand that. My question pertains more to the mechanics of getting the 80 minutes of audio on the CD, i.e., the source files. More specifically, there appears to be a megabyte constraint on the CD as well as a minute constraint. With that in mind, is it possible to have 72 minutes of audio but the combined file size of the source files exceed the disk capacity, even though the minutes are within the CD capacity? (Remember, I'm not talking about merely copying mp3 files to the CD...I'm talking about burning an audio CD.)

[yoda313]

I guess I'm more curious why you are asking.

What is your goal? What is your need?

There are extended play cdrs you can buy - 90 minutes and 99 minutes but they are out of spec and will not work on many cd players - it would be near impossible to find a list of exactly which cd players do play them. That would be a desperate measure.

Is this just a technical question or is there a practical application you are looking for?

As far as total playing time it is far more economical to get an mp3 player of any type or description. Or to invest in a cd player that plays mp3's off discs. They have portable and car models that play mp3s off cdrs. The original files not burnt as audio.

If you let us know what you're getting at we could offer more tangible real world advice if its not just semantics.

WAV format hypothetically taking up 1,000 MB of disk space

This might be your confusion point. Wav 16 bit at 44.1khz at cd level is a fixed format. YOu can't get any more or less than the fixed bitrate at that recording level. It will always be the same. So hence the 80 minutes on a 80 minute cdr or the 74 minutes on a 74minute cdr (or is it a 72minute disc???). - in other words it is a cbr constant bit rate - no ups or downs just one hard number.

[jman98]

The "Red Book" audio CD standard states that the audio MUST (NO EXCEPTIONS!) be 1411.2 Kbps LPCM (this is equivalent to standard WAV format). This is the limiting factor. If you do the math using the capacity of the disc you'll see that an 80 minute blank only allows for 80 minutes of audio meeting this specification. There is no "minute constraint" per se. It's really a capacity constraint measured in minutes simply to make it easier for non-techies to understand. You cannot play with the bit rates in audio CD to squeeze more audio onto a disc. However, you can do "overburning" to get up to about 2 extra minutes of space by writing to the lead out area. You can also use non-standard 90 minute (easier to find and burn and higher compatibility) or 99 minute (harder to find, burn and less compatible) discs if you need more space. Overburning on 90 and 99 minute discs is NOT recommended and most likely will fail.

[johns0]

Doesn't matter what size the original audio files are,they will always be converted to audio cd.

[yoda313]

that the audio MUST (NO EXCEPTIONS!) be 1411.2 Kbps LPCM

Thanks jman98. I couldn't remember what the wav bitrate was for cd audio.

[Opv]

Sorry my question wasn't made more clear. I presumed the stated presumptions (80-minute CD, and two sets of audio files, each set containing 72 minutes of audio but one set being in WAV format and the other in MP3 format) were sufficient.

My question springs exclusively from idol curiosity. I was talking with my brother earlier and he told me that he was having trouble burning an audio CD. He told me he was using a CD (stamped 52X 80 min or 700 MB on the label). He then told me that his source files for burning were in WAV format and that the total size of the WAV files totaled 748 MB. When he selected the files from within his burning software, it indicated that he had a total of 72 minutes of audio. However, when he attempted to burn the files, he received a message that the selected files exceeded the CD capacity. He ended up having to burn the files to two CDs.

That just didn't make sense to me, as I thought 72 minutes of audio would fit on an 80 minute CD, regardless of the file size or format of the source files. Hence, my question.

[yoda313]

Was this a really old burning software? Maybe it doesn't recognize 80 minute discs? Was there a slider to tell it to use 80 minute discs?

I would just use another 80 minute disc. Maybe it was a bad disc. Was it already partially burnt but not finalized hence not a completely blank disc?

[Opv]

Was this a really old burning software? Maybe it doesn't recognize 80 minute discs? Was there a slider to tell it to use 80 minute discs?

I would just use another 80 minute disc. Maybe it was a bad disc. Was it already partially burnt but not finalized hence not a completely blank disc?

Unfortunately, I don't know the answer to the question about the age or functionality of his software. He advises that the CDs were new out of the box.

Can you explain the phraise, "1411.2 Kbps LPC." You indicated that is the standard WAV format. Can a WAV file be saved at different bit rates similarly to the way an MP3 can? I thought WAV was a fixed, standard format, so that the identical audio saved on different machines using different software would still end up being the identical size and format on the disk.

[yoda313]

Can a WAV file be saved at different bit rates similarly to the way an MP3 can? I thought WAV was a fixed, standard format, so that the identical audio saved on different machines using different software would still end up being the identical size and format on the disk.

Wav can be saved at just about any bitrate.

But for it to be playable as an AUDIO CD it has to be at that fixed rate. No way around that.

So yes you could set a wav file on a computer to any spec you want and play it back on another computer without a problem. But it has to meet the specific requirements for audio cd in order to be burnt as a proper cd for regular playback.

[Opv]

Thanks.

OK, so let me see if I have my original issue straight. Assuming that the WAV is in the standard format, am I correct that 72 minutes of audio should fit on an 80 minute CD? If so, it sounds like my brother's software (or possibly the burner, itself) could be causing his problem.

[yoda313]

Thanks.

OK, so let me see if I have my original issue straight. Assuming that the WAV is in the standard format, am I correct that 72 minutes of audio should fit on an 80 minute CD? If so, it sounds like my brother's software (or possibly the burner, itself) could be causing his problem.

Exactly.

Don't forget to check the discs too. They could be faulty. Try a different batch of discs.

[Opv]

Thanks.

[Cornucopia]

What goes onto an AudioCD is only one type of file: a raw, headerless LPCM data stream. It is 2 channel, 16bit, 44100Hz, uncompressed. (similar to but not the same as WAV, which has headers and is byte ordered differently)
This amounts to 2 (bytes/channel) * 2 (channels/sample) * 44100 (samples/second) = 176400 Bps. Multiply that times your time and that's how much space it takes up.

For 72 min. = 72 (minutes) * 60 (seconds/minute) * 176400 (see above) = 762048000 Bytes, or 726.74MB. ALWAYS.

The problem that you, your friend, and many many others have with this is figuring out HOW this fits onto a CD.

Well, for all our purposes, you could say there are 3 kinds of CDs (or rather 3 ways to burn a CD): Audio mode, Data mode1 and Data Mode2form2.

Audio mode uses 2352 Bytes/sector. You use it for burning standard Audio CDs.
Data mode1 uses 2048 Bytes/sector. You use it for burning standard Data CDs.
Data mode2form2 uses 2324 Bytes sector. You use it, along with a small track of data type above, for burning standard Video CDs/SVCDs.

So it all comes down to not how many MB or Minutes does a CD hold, but how many SECTORS does it hold?

For 80 minute CDs = 360,000, 72 minute = 333,000.
So for AudioCD = 360000 (sectors) * 2352 (Bytes/sector) = 846720000 Bytes, or 807.49MB. Enough to fit your music clip above.
For DataCD = 360000 * 2048 = 737280000 Bytes, or 703.125MB. NOT enough to hold your clip.
For VideoCD it would be somewhere in between these 2 but leaning toward the larger capacity. But you aren't making a VideoCD so we'll ignore that for now.

Wait, you say. I'm not making a Data CD either. Aaaahhh, but I think you were. Even though you didn't mean to.

If you're not a power user of CD burning, it's easy for the user or the program to make that mistake.

*********************

Well, what about your 72 minute MP3 file mentioned in the OP?
If you make an AudioCD, this will HAVE to be converted to LPCM, but since it's only 72 minutes, it will fit.
It will also fit on a Data CD it its original MP3 form.

What if it were 90min?
It wouldn't fit as an AudioCD, but would as a DataCD (unconverted).

Clearer?

Scott

[AlanHK]

Sorry my question wasn't made more clear. I presumed the stated presumptions (80-minute CD, and two sets of audio files, each set containing 72 minutes of audio but one set being in WAV format and the other in MP3 format) were sufficient.

My question springs exclusively from idol curiosity. I was talking with my brother earlier and he told me that he was having trouble burning an audio CD. He told me he was using a CD (stamped 52X 80 min or 700 MB on the label). He then told me that his source files for burning were in WAV format and that the total size of the WAV files totaled 748 MB. When he selected the files from within his burning software, it indicated that he had a total of 72 minutes of audio. However, when he attempted to burn the files, he received a message that the selected files exceeded the CD capacity. He ended up having to burn the files to two CDs.

That just didn't make sense to me, as I thought 72 minutes of audio would fit on an 80 minute CD, regardless of the file size or format of the source files. Hence, my question.

In this case I think the burning application, or perhaps the burner itself, could not recognise the real capacity of the blank.
So it assumed a lower, standard, size. Or, you may have to enable "overburning" in the application to do this.

I've put over 80 minutes on a standard CDR, to combine a double album into one disc at original quality.

And you're right, the source format -- wave, MP3, whatever, has no bearing, they're all converted to the same format and only the total duration is important.

[Noahtuck]

That just didn't make sense to me, as I thought 72 minutes of audio would fit on an 80 minute CD, regardless of the file size or format of the source files. Hence, my question.

Well if you wanted to make an MP3 disc you could put quite a few hours of music on it, but then it would only play on hardware that was capable of playing MP3 disc's.

And maybe i missed it, but did you ever say what the burning program was ?

Don't forget to check the discs too. They could be faulty. Try a different batch of discs.

CDR's are not the same as DVDR's, i have used the cheapest no name brand of cdr's with really no issue except maybe how the back covering was made and could be scratched off easily when you did not take care of them.

Oh wait, i take that back, i did have some "silvers" from oversea's that went bad after like 15 years, not real "silvers" but the plain jane cdr's that just had a shiny silver backside for writing on.

But for the last decade plus, they all seem to be pretty much the same, even though i have my specific preference for CDR's.

@ Cornucopia

Clearer?

Do you intentionally try to make newbies head's implode or is it just a coincidence ?
LOL!!

[Cornucopia]

I went into my Dad lecture zone and just couldn't get out!

BTW, to add to the info for those wondering: DVDs & Blu-Rays ONLY have 1 mode - equivalent to Data Mode1.

Scott

Noahtuck, I got a spindle of CDs for free that were meant to be burned as "Music samplers" but had gotten the wrong tracks preprinted and so were worthless to use for the client.
Unfortunately, EVERY one of those discs lost their coating and became unreadable within 2 years!!!!
Had to do a LOT of scrambling to recover what I could. Quality means everything.