Burrrn and MP3s

[Fantome]

When burning MP3s to a CD, how do you know when you've added more than a CD will allow? When you go over the limit, Burrrn doesn't let you know.

[Soixante]

A normal cd holds 80 minutes of audio undless you have a 74 min or 90 min cd-r..So all you have to do is look at the cd length reported bt Burrrn




MP3 DISC

The way to answer that question is to take a look at how MP3's are encoded. Most MP3's these days are encoded with a variable bitrate. A variable bitrate (VBR) is how many bits per second does a particular file contain. The more bits, the better reproduction of the music. VBR allows files to use more bits when needed, and less when not, achieving a balance between file size and audible quality.

The other way to encode MP3's is Contant Bitrate (CBR). With CBR, a bitrate is specified at encoding time and that number is never deviated from.

So, how many minutes can fit on a 700MB CD?

If you have a constant bitrate file at 192Kbps (192,000 bits per second) that means that each second of music will contain 24,000 bytes (192,000 BITS divided by 8 to get BYTES). 24,000 bytes/second equals 1,440,000 bytes per minute (or 1.44 MB). Knowing that, we divide 700MB by 1.44MB and you can fit around 486 minutes worth of songs on a CD. There is some file overhead, so that number might be a little lower, but it's in the right ballpark.

The math is easy enough to adjust for other constant bitrates. Here's the whole formula:

minutes per disc = 700 / ((192,000 / 8) * 60)

or, more generically:

Minutes per disc = <disc size> / ((<bitrate> / 8) * 60)


For variable bitrate files, it's a bit harder, since potentially each second of each file can have a different bitrate. I believe the maximum bitrate (or at least the most common max bitrate used), even using VBR for MP3's is 320Kbps, but I could be way wrong. I think the best you can hope for here is to establish min and max values. Say you're encoding a music file that can bounce between 128kbps and 320kbps as needed, using the formula above you could deduce that you could store between 291 and 729 Minutes of music on the disc. Which, oddly enough, probably averages out somewhere near the mark for a 192kbps CBR file

Hope that helps.

[dphirschler]

And if you are too lazy to look at the total time (or just miss it), I believe Burrrn warns you before actually writing to the disc.


Darryl

PS. I just reread what I wrote and I didn't mean to come across as condescending. Please don't read it that way.

[hech54]

When burning MP3s to a CD, how do you know when you've added more than a CD will allow? When you go over the limit, Burrrn doesn't let you know.

As simple DATA or are you looking to make an audio CD?

[Fantome]

And if you are too lazy to look at the total time (or just miss it), I believe Burrrn warns you before actually writing to the disc.

Nope. No warning, which I found strange.

PS. I just reread what I wrote and I didn't mean to come across as condescending. Please don't read it that way.

I didn't.

As simple DATA or are you looking to make an audio CD?

Simple data. With audio I know just not to go over 80 mins. since I'm using 80 min. CDs. I guess I have to know the bitrate and do some math as Soixante described. Thanks Soixante.

[hech54]

[Simple data. With audio I know just not to go over 80 mins. since I'm using 80 min. CDs. I guess I have to know the bitrate and do some math as Soixante described. Thanks Soixante.

That makes ZERO sense. Bitrate has ZERO to do with creating a CD full of MP3 files.

[dphirschler]

If you are making a data CD, then use InfraRecorder instead of Burrrn. Burrrn is better suited for audio CDs (does it even do data CDs?).


Darryl

[t0nee1]

[Simple data. With audio I know just not to go over 80 mins. since I'm using 80 min. CDs. I guess I have to know the bitrate and do some math as Soixante described. Thanks Soixante.

That makes ZERO sense. Bitrate has ZERO to do with creating a CD full of MP3 files.

For Audio CD I have to agree, but for creating a CD full of MP3 files, the lower the bitrate the smaller the file size and hence more mp3s will fit the data disc..Nitpicking , I know!..

And no, burrrn does not create Data CD's..