[Instigator99]

I'm currently converting some tapes and LPs to CD. (I'm using an Audigy board from Creative labs, but I think this is a generic question, not specific to that hardware or software.)



I noticed that immediately after I've gotten a file onto my HD, before any further work is done by the Audigy software, the file size is typically in the range of 200--250 MB, which strikes me as about right (2 tracks, 20--24 minutes of material, etc.)



But after the Audigy software has done some sort of conversion on the file, removing hiss, pops, etc, the file is typically around 20--25 MB. When I click on this file and play it with (say) WMP, it plays fine. But a few times, when I've burned about 40 or 45 minutes of material to a CD, I sometimes get a warning from the software stating "there might not be enough space on this [new, blank] CD to hold all this."



I'm having trouble understanding these numbers. A blank CD will hold 80 minutes of material, or 700 MB. So if a 20 MB file that I can play on my machine, represents (very roughly) 20 minutes of material, (I assume there's some sort of compression or encoding going on) , why can't I write 35 such 20-minute sessions to the disk (20MB X 35 )--IOW, 700 minutes, rather than 80?



Or is it that when the file is written to a CD it must be expanded?



There's gotta bea simple explanation of this somewhere. I just have not found it yet! Appreciate all help or links I can get on this. Tnx.

[rgreen4]

The size of a digital audio file on disc or a drive is a direct relation to the compression used when converting the file. There are several audio formats, and one (mp3) even has different sampling rates. These will affect the size of an audio file. For MP3 files common bit rates (compression) are 32, 64, 128, 192 and 256. There are others and the top is 320 kb/s. This means for every second of sound the file will take 320 kilobytes. If you use 32 kb/s you would get 10 times the amount of music on a given disc, but the sound quality would be badly compromised.
If you are converting to MP3 files, and have 45 minutes of music filling the CD, it would indicate the sampling rate is 256 kb/s. (45 min x 60 sec x 256kb/s = 691,200,000 bytes or 659MB which would nearly fill a 700MB CD. The sampling rate of 256 kb/s is a high quality, by going to 128 kb/s you can double the amount of music, but the sound quality will be degraded somewhat.

[Instigator99]

Tnx for your message. I should have said that this is a WMA file on my HD, and I click on that WMA file to play it with WMP. I understand about sampling rates etc (in fact, I think it was the Bell Labs genius Claude Shannon who was the pioneer in this stuff, and long ago I read some of his work.)



Here's the part I don't get: the output of the conversion process starts out as a WMA file, e.g l.213 MB. Then it goes down to a 23(roughly) MB file. Is the smaller file, a compressed file? When the file is written to the CD to create an audio CD, I recall that it's expanded again so that typically 20 or so minutes of audio will take up 200+ MB on a CD.



So how come the same file can be 20 MB on my HD, and 200+ on the CD? That's the part I don't get. It's the same software playing either file, on the CD or the HD.

[rgreen4]

When you mention that the file is 20MB on HD and 200MB on CD, you must be talking about the entire album. But even then, the WMA compression is high. I have burned a number of songs to my HD from CD, (all are mp3) and one that I just sampled is 3:53 long and takes 9MB on the HD at a bit rate of 320kb/s. I am not sure what bit rate WMA uses, but you may also be burning the CD as a music CD rather than simply copying the files onto the CD.

If you want to get more on the CD, then instead of burning the CD from the collection of music, simply burn the files onto the CD as a data CD. Now this requires that the audio player you use must be able to read WMA files, which is not always the case. When burning the audio collection onto a CD as an Audio cd, the files are converted back to the native files they were in on the original CD which do take more room. Typical max is 25-28 audio tracks on a CD. Note that many collections of various music files will have multiple CD's if they go over this amount. I am looking at one with two CD's and has 25 tracks on one and 26 tracks on the second. Which is 75-77 minutes on each CD. Each CD of the 2 CD set occupies 177MB of HD space when converted to mp3 at 320kb/s, yet maxes out the CD in it's native CD music format. Looking at the original in Windows Explorer only show the .cda files which contain the track info not the actual audio tracks.

One of the reasons I use mp3 even though I play my music in Windows Media Player 11 is that I can copy the mp3 files to a CD and then play it in my car.

Pulling audio from phono's and tapes sometimes will also put all the audio tracks in one audio file after conversion. If this is happening you may want to convert each song individually. This will take a lot more time, but gives you more flexibility. I have not done this yet, but I am going to undertake a project like this later this year.

[smax013]

The short answer (as kind noted by [~22087]) is that WMA is still a compressed format. If you are burning the CDs as music CDs, then the music files are being burned to them as WAV files that are uncompressed. If you want to keep those files as 20 MB files or so, then you have to burn them to the disk as data files NOT music files...but then any device that you want to play them on will have to be capable of playing WMA files...which many older CD/DVD players will NOT do.

[mjd420nova]

Many things have a big effect on file sizes when converting any audio input source (LP's, cassettes or other CD's). Inputing into a sound card line input connection, you have many choices to use for sampling. Music CD's that you buy in the store are recorded in PCM stereo, 44kc, 16 bit .WAV format and take up roughly 10 megabytes per minute. Changing to 24 bit sampling that many cards have available will give better fidelity but can only be played back on another PC with 24 bit capablity and not on the normal CD player. Compressing the music to reduce the memory space used as with MP3 format will yeild good results but you may notice some loss of music content. CD players can be purchased with this MP3 ability. I preserve all my music in the 16 bit .WAV format to make it accessable to any user. I have transposed LP's(33 rpm), 45's (45 rpm) and the much older 78's (78 rpm) vinyl platters this way beside scores of cassettes, eight track, quadraphonic tapes and some four track studio format tapes this way and them burn them to CD's this way and been very pleased. I have experimented with many lossless compression formats but haven't found one that preserves the music without some loss of fidelity. This was done in a laboratory with single and dual sources, using sine waves, square waves and triangle waves that are rich in harmonics to best replicate music waveforms and found them to be lacking in that any compression scheme has to remove some content via a mathematical algorythum but cannot replace the missing content by decompression once it is removed from the data.

[Instigator99]

Ahh, now this is the kind of concise answer I was looking for. Nicely explained. Tnx.



Your answer suggests that if I want to archive these files on a CD (rather than play them), I can do it in the WMA format, and play the file on my computer, if I want.

[Instigator99]

Smax, my response immediately above was of course directed to you. Many tnx.