can anyone provide a scale of the minutes worth of mp3 files held by various sized mp3 players.
I have an IPOD, the files seem to be large as I only have a medium sized cd collection (100) and have used 2.4 gb of the 30.
The scale is to decide on a machine for my daughter

Based on songs at 4MB per song, you can fit about:

32 songs on 128MB
64 songs on 256MB
120 songs on 512MB
240 songs on 1024MB (1 Gigabyte)

As music tracks vary it's difficult to say exactly how many minutes of music you'd get. But supposing each music track is 4 minutes in length, you'd get 128, 256, 512, 1024 minutes with 128MB, 256MB, 512MB and 10245MB respectively.

It is all dependent on the bit rate used.

A song encoded to the same format as a CD has a storage requirement of about 10MB per minute of stereo audio.

An MP3 file at 128kB/s will require a shade under 1MB of storage per minute. Obviously different bitrate MP3 files will use more or less storage in proportion (higher bit rate more storage obviously )

So if you use 128kB/s MP3 files the number of minutes of audio you can store on any device is roughtly the same as it's capacity in MB. As a very rough guide that is

of course the other to go is don't believe the song total that the companies advertise, as they normally use a lot lower compression rate, whilst it does give you more songs the quality is prety awful. I personally use either 192 or 256 for my music, but having a 20GB I have the space to do as I'm not bothered about having 5000 songs on it.

Mine are all encoded at 128k and i've got a 3/4 full 20gb player, it equates to 5250 songs at the current rate.

128k sounds terrible at loud volumes.

Let's eb honest 128 sounds pretty awful full stop. That's why ia m at present changing most of tracks to 192 or 256. The difference for instrumental music is quite marked between 128 & 256. I can see why some people have their music at 128 just so they stuff their player with as much music as possible. But it can take a lot of time to actually get through about 4,000 - 5,000 tracks. But whatever rocks your boat i guess.

Just out of idle curiosity...

How are you re-encoding your mp3s? I hope you are doing it the "proper" way which is to go back to the source CD and re-rip/encode to a different bitrate.

The "wrong" way is to take your original 128kb mp3s and re-code to 256kb All that does is double the size of the file and DEGRADE the sound compared to the 128kb original ! In fact if you do not have the original CD of any the tracks you would be better off leaving them as 128kb.

For the curious the reason for this is inherent in the way MPEG works. A CD format track is about 1.4Mb/s so to reduce that to 128kb/s a shed load of information has to be discarded, about 90% in fact! (no wonder they sound c**p!! ) It does this by ignoring bits of audio that it thinks are inaudible. Trouble is once these bits of audio are discarded they are gone for ever and cannot be re-created. (a very simplistic and crude explanation I know)

So a 128kb/s mp3 converted up to 256kbs does not have any more audio information than it had in the original 128kb/s file. In fact it is likely to have even less as the re-encoding process inevitably strips out a little bit more!

I work with varios flavours of commpressed audio formats professionally. I always advise my colleagues to avoid copying files between formats, or even the same format too much as it always degrades the sound quality. A general rule of thumb is no more than three passes through an encoder stage. Any more than that and you can turn a finely tuned concert grand piano into the kind of thing you see being played in the saloon in cowboy movies

I re rip them from CD. Or if I don't have them on CD I down them from allofmp3 as I can decide the kps not the record company plus no stupid dumb DRM.

Think of it as around a megabyte a minute give or take. mp3's usually take up about a tenth of the space of WAV files.

Only at 128kb/s bitrate though. Not all mp3s use this bitrate so you cannot really make generalisations of this kind.

The way to work out how many bytes per minute you need is fairly simple. Multiply the bitrate in kb/s by 60,000 (1000 bits per kb, 60 seconds per minute) then divide the result by 8 (8 bits per byte). This gives you the number of bytes in one minute of audio.

Now comes the 1000/1024 bytes per kB arguement. But if you use the Microsoft standard for measuring kB/MB divide the above figure by 1024 to get the file size in kB and a second division by 1024 to get it in MB.

If you do that for 128kb/s mp3 you get

128x60,000 = 7680000 b/m
7680000/8 = 960000 B/m
960000/1024 = 937.5 kB/m
937.5/1024 = 0.91552734375 MB/m

where B = Bytes and b = bits and /m = per minute.

Which means that if you use 128kb/s format multiply the capacity in MB of the player by 1.1 to get the approximate number of minutes it will store (not allowing for any file system overheads).
Last edited by chrisjr : 02-11-2006 at 12:25