Music CD-R holds a total of 260 MB of "lossless" audio?

Question

I just ripped a full (all 74 minutes used) Music CD-R to six .flac files, one for each track. In total, the files add up to 262.1 MB. I thought a CD was supposed to hold 700 MB. Where did the other 440 MB go?

Answer 1

It depends on several factors. "The audio contained in a CD-DA consists of two-channel signed 16-bit Linear PCM sampled at 44,100 Hz." This means 176400 bytes/second (2 bytes per channel, times 2 channels, times 44100 samples/second).

By definition a CD-DA should fit 74 minutes of audio at this sampling rate, meaning (176400 * 60 * 74) = 783,216,000 bytes, or 746.93 MiB.

Now, please notice that this is simply raw, sampled audio with no compression whatsoever.

So assuming you were to rip a CD with an actual play time of exactly 74 minutes, to an equivalently-raw format such as WAV or AIFF, you would get close to those 746 MB of information.

Your data is smaller due to two factors.

First, your disc may not be entirely full. Many CDs simply don't contain all possible 74 minutes of information. To put an example, The Beatles' Rubber Soul contains only 36 minutes of music, so it would contain less information.

Second, and perhaps most important, FLAC may be a lossless format, but it's not compressionless. To quote Wikipedia:

"FLAC (/ˈflæk/; Free Lossless Audio Codec) is a codec (compressor-decompressor or coder-decoder) which allows digital audio to be losslessly compressed such that file size is reduced without any information being lost. Digital audio compressed by FLAC's algorithm can typically be reduced to 50–60% of its original size"

So if you assume that your 262 MB of audio are compressed by 50%, you'd come up with 520 MB of raw, uncompressed audio, which translates to a play time of about 55 minutes.

Add up the runtime of your tracks and I'm pretty sure it'll be close to this figure.

References:

• http://en.wikipedia.org/wiki/Compact_Disc_Digital_Audio#Storage_capacity_and_playing_time
• http://en.wikipedia.org/wiki/Rubber_Soul
• http://en.wikipedia.org/wiki/FLAC#Compression_levels

Answer 2

.flac is a lossless compression format. It compresses the files so that they become smaller in size. That's why the total is less than 700MB.

Answer 3

CD-R discs do have a capacity of 737,280,000 bytes (700 MB), if they're not defective. But, a music CD can be made with less than the maximum capacity, so if the flac files add up to less than 700MB, that might not be a problem.