Audio CDs and MP3

[stormx]

Hi,

i am a CD collector (i have about 400 original CDs). I never liked the idea of illegally downloading music from the net, nor copying it. Basically, for 2 reasons:

1- Ethical. No further comments are necessary, i beleive
2- I like to have the original CD, with its case and inside notes

So, because i do have the original CDs, i listen to them in a discman player when i am out. However, it seems that discmans are old fashioned nowadays, when you have MP3 players with gigas of capacity being 10 times smaller in size.

Questions:

If i convert my audio CDs to MP3 format (which is the best program to do this?), will be the sound quality loss be really noticeable? Let suppose that the conversion is done preserving the best quality possible.

Do you beleive the long work of converting my 400 audio CDs into MP3 format worth the time?

What do you think??

Thanks

[minor9th]

It depends on the quality of the playback equipment. If you use high quality headphones or play through a high end stereo, this will be a slight loss of dynamics, and perhaps a slight loss of clarity (likely due to the compression). However, played back with typical supplied headphones or in the car, any loss will be negligible.

[stormx]

Thanks for your reply.

I do not have either a particular gifted ear, so possibly the quality loss would be even less noticeable for me 

Follow up questions:

1- What program do you use for such a conversion (audio-MP3)?

2- How much space does an 80 minutes CD takes, when converted  to MP3 format (with good quality)?

3- Does the conversion process take too long?

[Kassaa]

For the conversion I use Winamp Pro, when converted to a good format it takes around 100-110MB, in the best format around 160. The conversion time depends on the quality, with high quality it takes around 10 minutes for one CD.

[richard black]

If you get yourself a good, modern portable player with a hard disc you can store your CD recordings as native CD data ('WAV' files) or losslessly encoded if the player supports it ('FLAC' files) which effectively doubles the storage capacity with no loss in quality. I find all MP3 files, even at the highest data rates, very annoying to listen to and far from getting accustomed to MP3 effects, most people find them more annoying over time. That said, it does depend somewhat on the music you want to listen to - solo piano survives pretty well, actually.

If you do decide you want to maximise capacity and compress, consider using MP4, also known as AAC. Many modern players support this and it's considerably better than MP3. No, there isn't a super-high-quality MP5, not even as a proposal!

[landru]

Follow up questions:

1- What program do you use for such a conversion (audio-MP3)?

2- How much space does an 80 minutes CD takes, when converted  to MP3 format (with good quality)?

3- Does the conversion process take too long?

1. I use Exact Audio Copy in conjugation with the LAME mp3 encoder. I wish I could tell you how to obtain them (they are freeware) but I've forgotten. But by googling you should be able to find the tutorials to use them.

Basically, the idea behind the LAME encoder is that it dynamically adjusts the sampling bit-rate according to the complexity of the music- if the music can be represented by sampling at low rates it does so, and if it needs to cram more samples per second to be accurate it does that.

The "problem" with most mp3 encoders (Apple, Winamp etc.) is that you can only encode the whole piece at one sample rate. So if you want to make a mp3 of a Mahler symphony, you might choose a high sample rate to catch most of the music without unacceptable distortion, and then have a humongous file to deal with. The LAME encoder makes sure that you can balance file-size with "acceptable" reproduction. Most of the sample may be at a low sample rate, but when all 200 pieces of the orchestra start playing at once - you want as much sampling as you can get!

You are still left with an mp3 file that has left out information from the original. Some people can hear the difference very readily - some can't or it doesn't matter as much. For me, getting my music into digital format on my hard drive makes it more accessible

2. What I've found is that a good rule of thumb is that every 10 minutes of music corresponds to 10 MB at higher compression rates. So 80 minutes -> about 80 MB. Though with LAME it all depends on the music.

3. The conversion process is mostly dependent on the speed (and accuracy) of your CD-ROM drive. You could have a fast drive, but the error correction could be so lousy that it could still take a long time. A CD usually takes about 5-10 minutes.

[maul]

Just make sure you encode them at 320kbs. Anything else is just, well, newb.

[pianolearner]

There are some good answers here, but just to clarify some technical misconceptions.

1) WAV files are NOT native CD format. They are 2 entirely different standards.
2) Sampling Rate is frequency dependent ie/ The higher the frequency, the higher the sampling rate needed. It has nothing to do with the number of instruments playing at the same time. I suggest people read more about the Nyquist frequency.

[richard black]

WAV files are NOT native CD format. They are 2 entirely different standards

They are the same in the sense that matters, i.e. a WAV file retains the exact data on the CD, bit by bit. I work with this stuff for a living and have _many_ times proved that the WAV files on my PC are bit-for-bit the same as the data on the CD - I check it as a matter of course when CDs I've mastered come back from the factory.

Sampling Rate is frequency dependent ie/ The higher the frequency, the higher the sampling rate needed. It has nothing to do with the number of instruments playing at the same time. I suggest people read more about the Nyquist frequency

The terms 'sampling rate' and 'bitrate' (bit rate, bit-rate?) get a bit confused sometimes, and no surprise. Sampling rate is generally defined for a format (e.g. for CD it is 44100 samples per second) and in turn it defines the maximum frequency you can record. Most MP3 files are at that same sampling rate, though others are possible. It is technically possible to have non-constant sampling rates but it's a bit pointless and never done. Bitrate of MP3 (etc.) files basically tells you how much data compression has been done. Variable bitrate (the 'VBR' setting which as someone pointed out is supported by LAME and _some_ other MP3 coders) gives a higher bitrate when the music demands it and lower when the music allows it.

To answer the question about how much space an 80-min CD takes up:

As WAV files, 800MB = 0.8GB (10MB - megabytes - per minute almost exactly)
As 128kb MP3 (the commonest bitrate), 80MB
As 320kb MP3 (the highest available bitrate), 200MB
As typical VBR, roughly 100MB, give or take at least 20% depending on settings and the music you're encoding.
As FLAC files, which I mentioned earlier, 300-400MB depending on the music.

[pianolearner]

They are the same in the sense that matters, i.e. a WAV file retains the exact data on the CD, bit by bit. I work with this stuff for a living and have _many_ times proved that the WAV files on my PC are bit-for-bit the same as the data on the CD - I check it as a matter of course when CDs I've mastered come back from the factory.

Yes, but this is still misleading. Native means in essance, exactly the correct standard. A WAV file isn't always exactly the same standard as an audio CD because you can record a WAV from an analog source with different sampling rates. Native would imply that if you have a WAV file it is recorded as defined by the RED BOOK standard which specifies the form of digital audio encoding: 2-channel signed 16-bit PCM sampled at 44100 Hz. WAV is a Microsoft and IBM audio file format standard for storing audio on PCs. It does not specify sample rates or the number of channels.

[pianolearner]

Sample Rate and Bit rate are interrelated. It's nothing more than a case of simple arithmetic. There are 8 bits in a byte.

ie/ Bit Rate= (Sampling Frequency ) X (Sample Size) x (Number of Channels)

For example, the Bit rate for an Audio CD is:

Bit rate = 44100 samples/s × 16 bit/sample × 2 channels = 1411.2 kbit/s (more than 10 MB per minute)

[richard black]

OK, fair enough, WAV is indeed a broader standard than CD but if you get the raw data off a CD the default WAV file you will create (i.e. unless you quite deliberately process it) will be the same bits. There are several other formats to which you can convert the data (AIFF, for instance) which differ only in trivial stuff like header information and byte order.

Bit rate and sampling rate are only directly related for linear PCM. MP3 files are compressed so the bit rate is (sampling rate) times (word length) times (number of channels), divided by (compression ratio), which last parameter depends on setting and in the case of VBR is non-constant.

Bit rate = 44100 samples/s × 16 bit/sample × 2 channels = 1411.2 kbit/s (more than 10 MB per minute)

10.584MB per minute, indeed. Or 10.3359375MB, or possibly 10.09368896484375MB, depending on whether you like your mega to be 1,000,000, 1,024,000 or 1,048,576.