CD limits

MajorFoley · April 20, 2019

Cannot believe i am asking this question, so parents friends wants his music put on CD's (apparently car doesnt have a USB plug) and i said i'd do it while they are down. So i got some 700MB discs with about 80 min length time and using imgburn. When i go to create the disc with files that get to about 76 minutes (close to 100% according to imgburn) but the files themselves are around 300mb, Imgburn says its about 807MB while burning! This normal?

mariushm · April 20, 2019

Audio CDs store music in uncompressed form.

So each second of audio uses 44100 Hz x 2 channels x 16 bit (2 bytes) per sample = 4 x 44100 = 176,400 bytes per second.

So 76 minutes of audio will use 76 minutes x 60 seconds x 176400 = 804,384,000 bytes MINIMUM, or 767 MB

There is some empty space between each audio track, and some additional disc space is used to store some data that helps audio players detect tracks and other crap, so the 807 MB approximation is more or less correct.

If you're wondering how you could store 800+ MB on a disc when the disc says 700 MB on it, well, that's because CDs can actually store more than 700 MB on them. The 700 MB value is valid only for storing DATA, not when you're creating Audio CDs or for example VideoCD.

When storing data, a part of the storage space on CDs is used to store error correction information and other crap useful to correct errors when discs get dirty or scratched, for example it's something like for every 2100 bytes of data, around 400 bytes are used for error correction and other things.

When you're creating audio CDs or VideoCDs, the software uses ALL the available data for music or video, with the reasoning that error correction is less important - if there's a scratch on the disc and the unit can't correct the bits under the scratch, worse case scenario you'll hear a click or pop on the audio, or a single video frame would be partially corrupt (you'll see a bunch of green blocks on the screen for 2-3 ms)

Your 300 MB audio files are most likely compressed to MP3 or FLAC... that's why they use only 300 MB... on audio CDs the music is uncompressed, so the burner decompresses the music into uncompressed audio which uses more space.

You should ask your friend if their car player supports MP3 playback ... in that case, you may be able to simply put MP3 files in folders on a CD and burn a CD as regular data disc. Maybe keep the folder names short, like less than 30-40 characters, and as few subfolders as possible ( ex root folder > eminem > eminem - my best album > eminem - track1.mp3 should be ok ... more complex than that less recommended)

MajorFoley · April 20, 2019

19 minutes ago, mariushm said:

Audio CDs store music in uncompressed form.

So each second of audio uses 44100 Hz x 2 channels x 16 bit (2 bytes) per sample = 4 x 44100 = 176,400 bytes per second.

So 76 minutes of audio will use 76 minutes x 60 seconds x 176400 = 804,384,000 bytes MINIMUM, or 767 MB

There is some empty space between each audio track, and some additional disc space is used to store some data that helps audio players detect tracks and other crap, so the 807 MB approximation is more or less correct.

If you're wondering how you could store 800+ MB on a disc when the disc says 700 MB on it, well, that's because CDs can actually store more than 700 MB on them. The 700 MB value is valid only for storing DATA, not when you're creating Audio CDs or for example VideoCD.

When storing data, a part of the storage space on CDs is used to store error correction information and other crap useful to correct errors when discs get dirty or scratched, for example it's something like for every 2100 bytes of data, around 400 bytes are used for error correction and other things.

When you're creating audio CDs or VideoCDs, the software uses ALL the available data for music or video, with the reasoning that error correction is less important - if there's a scratch on the disc and the unit can't correct the bits under the scratch, worse case scenario you'll hear a click or pop on the audio, or a single video frame would be partially corrupt (you'll see a bunch of green blocks on the screen for 2-3 ms)

Your 300 MB audio files are most likely compressed to MP3 or FLAC... that's why they use only 300 MB... on audio CDs the music is uncompressed, so the burner decompresses the music into uncompressed audio which uses more space.

You should ask your friend if their car player supports MP3 playback ... in that case, you may be able to simply put MP3 files in folders on a CD and burn a CD as regular data disc. Maybe keep the folder names short, like less than 30-40 characters, and as few subfolders as possible ( ex root folder > eminem > eminem - my best album > eminem - track1.mp3 should be ok ... more complex than that less recommended)

Thanks for the explanation, i think it was MP3 player supported but i just did it this way cos it seems safer, if it works it works i guess. Means longer burn times (only burning at 10x) but if it works, which at least it does in mine but i have USB then it should work on theirs. Either way even with MP3 i would still need to use at least 5 discs because of 2 very long tracks they want too which go for 47 minutes alone..