CD file size doesn't match program time [SOLVED]


I’m preparing an audio-CD. When I use Audacity to prepare the tracks, the time at the end of the final track is 76min38s. I assume this should fit onto an 80min/700MB CD-R. When I export the files for CD burning, the run time of the tracks adds up to that same amount of time. However, the size of the files adds up to 792MB, and I can’t record it onto a CD, it’s too big. I thought that when you export in the correct format for CD-Audio (44100 HZ, 16 bit PCM), that 76min of music would come in under the 800MB limit. Further, I use IMGBURN to burn the CD, and it gives me the same file size as I get from adding up the individual files, but tells me there is 88min of music. I know there is only 76 min in the program, i timed it. Any idea what is going on, and how i can get the file size down so I can record this program on an Audio-CD?


Audacity 2.0.6; exe

Music on an Audio CD is not in standard file format. It’s basically a tight stream of gap-free music and an index area. If you try to burn a million audio files (99 max) the index file goes nuts trying to keep up. It’s never a good idea to bump up against the limit on Audio CDs. You get many surprises.

And that’s a standard Red-Book CD. If you insisted on putting song titles and other stuff on there with the odd Text option, it gets worse.

how i can get the file size down so I can record this program on an Audio-CD

Leave something out. There is no Red Book Audio CD compression. You have to sheer off minutes (or numbers of files). I don’t remember this exactly, but I think if you put one single music file on there, the size numbers get really close to the numbers printed on the disk wrapper.

If you know your audience can play it, you can totally make a Data CD with MP3 files on it. You can probably get three weeks of music on there, but it won’t play in your mum’s Buick.


I know this seems odd, but when it was designed, they had to find a tight data system that made no decisions. So the sound is always perfect 44100, it always has 16 bit depth, it never has titles, etc.


Thanks for the response. Cutting it down is Plan B, and I already have an ISO for that eventuality. But the question still exists; if the sound is 44100 hz and 16 bit depth, isn’t there a direct correlation between the recording time and the size of the data file? Just trying to understand, I’ve recorded a number of Audio-CDs with the process I’m using (Audacity ==> ImgBurn), always managed via recording time and never ran into this issue.


I don’t know anything about IMGBURN, but 1 minute of 44100 Hz 16-bit PCM stereo audio is 10.094 MB (to three decimal places) and so 76 mins 38 seconds of such audio is 773.536 MB (to three decimal places), in one file or many.

Where do you read 792 MB? Are you using Export Multiple and including unintended audio before the first label?


This get’s confusing, but are you sure you have “80 minute” CDs? Maybe try a different brand… Or, maybe it’s your CD burner?

If I have some time this weekend, I’ll try making an exact 80-minute file to see if I can burn it… Or, maybe I’ll try 79:59 to maker sure I’m not over by one byte or something…

I thought an original 74 minute CD could really hold 74 minutes and I thought an “80 minute” CD could really hold 80 minutes…

I also thought WAV files take-up more space than the same files in audio-CD format. (Due to “file overhead” or “formatting overhead”, or maybe it’s just the file header which adds around 40 bytes per file.)

There’s also confusion about how big a megabyte is!!! We think of it as 1 million bytes, but according to Wikipedia, it’s either 1,048,576 bytes or 1,024,000 bytes. Blank DVDs are usually sold as 4.7GB, then you find out they only hold 4.38GB (according to the way Windows counts GB).

In addition to comments from DVDdoug, there is a difference between “data capacity” (number of bytes of data that can be stored) and “audio capacity” (number of minutes+seconds of audio that can be stored), due to audio CDs using some of the available space for the table of contents and other format data.

Definitely 80 minute/700MB CDs. If I knock the file size down to 690MB by dropping a track, I can burn it, but the total music time is on the order of 62 minutes, way below 80!

There is a reasonably understandable explanation here:

The least confusing way I can think of explaining it is that:

  • CD’s can store more audio burnt as an audio CD than they can when burnt as a data CD, because in audio CD mode they store more user data per sector rather than using some space for purposes like error correction
  • CD size capacity is quoted for burning as data CD, but playing time is quoted for burning as audio CD.

I “think” this is why around 800 MB of WAV data can be burnt as audio CD on a “80 minute 700 MB” CD-R and not because the overhead of WAV files is removed from the PCM stream which could not account for that difference.

Or, I and others are still confused…


Apart from why you have a greater WAV file size than you should have, are you sure you are not setting IMGBURN to burn a data CD?


Do you get a dialog that offers to change the spacing between tracks or songs from the default 2 sec? That’s a setting for Audio CDs.


So, I’ve uploaded three image files. The first one,
Track List.png
shows the file size and the recording time of the list of .wav files I want to burn. If I add up the time, I get 76.55 minutes, or 76min33sec. If you add up the file sizes, you get 792MB

The next one is the Audacity project screen
, with the cursor at the end of the program, showing that the program is 76min38sec. So there is 5 seconds floating around somewhere, that isn’t big enough to make a difference.

The final one is the ImgBurn window just before you start the burn
. I believe it is set up to burn an Audio-CD (ISO9660, UDF 1.02). You will notice that the file size is 812,122,112 bytes (that discrepancy was explained in an earlier post). But the program time is shown as 88min9sec!

I’m about ready to throw the white flag and burn a CD under 700MB, but if you can help me understand if either I don’t have the burner set up right or I"m somehow saving the wrong thing out of Audacity, I’d really appreciate it.



Is there any reason you’re not using a conventional Audio CD Authoring Program?

ISO 9660 is a standard published by the International Organization for Standardization (ISO) in 1988. It defines a file system for CD-ROM media (data CD based on the Yellow Book specification) to support different computer operating systems such as Unix, Windows and Mac OS, so that data may be exchanged.

Unless someone corrects me, you are not making a Red Book Audio CD.


Side note. Accepting Maximum Burn Speed is almost always a bad idea. Some systems accept a higher than you think error rate just to get that burn speed up to look good in the advertisements.


To convert bytes to kB, divide by 1024 = 793088 kB
Assuming 44100 Hz, 16 bit stereo, to convert from bytes to minutes, divide by 10584000 = 76.73

From the length and file size, all of those files appear to be 44100Hz 16bit stereo.

I’m not very familiar with ImgBurn, but if I recall correctly, it creates a CUE sheet as a separate step. Have you looked at the CUE sheet to see if there are any anomalies there (such as tracks listed more than once)?

Why is the data source an ISO?

I suggest you follow or ask on their forums.

Or use iTunes or Windows Media Player to burn.


I just burned a CD 3 seconds shy of 80 minutes.

When I tried an 80 minute file ImgBurn shows 2 seconds more than 80 minutes. I get a warning that asks me if I want to truncate, overburn, or cancel. I canceled, trimmed 3 seconds off and tried again.

This was one “full concert” WAV file. I trimmed of the end to get the length I wanted and burned it as one track on the CD.

(That was an Audio CD made using an appropriate CUE file. The 79:57 WAV file burned as “data” did not fit on the CD as a WAV file.)

Yup, and that was exactly my problem. I first burned an ISO file, which I realized was not the right path, but when I created the CUE file, I I was burning from that file, but ImgBurn was still trying to burn from the ISO. Once I opened the .cue file directly into ImgBurn, it recognized i was burning an Audio-CD and set up correctly for that. My 76 minute program burned fine.

Thanks all for your help.