What the SD on MP3 Sound?

General Questions
#1

I had a guy I know make me a CD. It sounded great. It was a CD of Minnie Ripperton which I already own. When I worked out I listen to CDs and awhile back I lost the original so I figured if I made copies who cares if I lose the copies.

Now I also like old time radio, so I got some CDs that burn like 100 “Burns and Allen” shows onto one CD but in MP3 format. When I mentioned this he told me he could burn things in MP3 format as well.

This guy then burned me the same Minnie Ripperton CD in MP3 format and put more on to boot.

The question is the CD sounds OK in MP3 but not like the CD version he burned me at first.

So just to be sure, I had two other people I know, burn me some of the record to see if it was the format or the technique. All the MP3s sound the same but none come close to the first CD he burned nor the original.

Now I have a tin ear, so my question is do MP3 sound less than CDs. To me it was like the difference between a cassette and a CD version of a song. Is there a big difference. And if I can notice it surely others can.

Or am I not hearing it (in other words is it just me)

#2

I’m kinda confused - does this “CD in MP3 format” play in a regular CD player? I’m guessing yes.

If you rip audio directly off a CD, you’ll end up with a .wav file, which is uncompressed, 44khz audio. Layer 3 MPEG compression then squishes the file giving you an MP3. It should be no big surprise that the mp3 doesn’t sound as good as the original. OTOH, your CD now takes up 50M instead of 500 (and you don’t get this good compression with non-lossy formats).

A CD player is a dumb device and knows nothing about this, so when someone makes a regular CD from mp3s, your burner program will decompress the mp3s into raw audio (.wav-type) before writing it to disk. The data that got squished out in the first place - it ain’t coming back!

So there you go. Yes, most people can hear the difference if it’s side-by-side on good equipment. But when you’re using headphones on the bus, the only difference between an hour of ok-music and 5 minutes of great is the time.

#3

Markxxx:
The quality of an mp3 depends on its “bitrate”. Uncompressed CD audio is about 1400 kBps. (kilobits per second)
I think mp3’s that are at least 160 kbps are good… 192 kbps is even better, and I think the maximum bitrate for mp3’s is 320 kbps. Note that people often make 128 kbps mp3’s - their lesser quality is fairly noticeable.

Apparently some formats like ogg, wma and aac(?) sound about as good as mp3’s do that have twice the bitrate… so a 64 kbps wma is meant to sound about as good as a 128 kbps mp3. On the other hand, things like wma and aac(?) can have copy protection built into them… ogg is an open source format though it isn’t very popular.

#4

While we’re on the subject, is AIFF a lossless format? I’ve been using it when I want to burn a classical music CD through iTunes (i.e. when a lack of distortion is important), but maybe I shouldn’t be.

#5

AIFF is lossless. MP3s vary in quality depending on bitrate and the encoder. I don’t really do much of this stuff myself, but I’ve heard that LAME is probably the best encoder out there (contrary to its name!)

#6

Markxxx, here’s another way to think about it. We all know mp3 is a compressed format. At 192kbps the compression ratio is 7.4:1, roughly meaning the compression algorithm is discarding 7.4 bits for every one bit it leaves remaining. At 128kbps stereo, the ratio is 11:1, you’re listening to only approx. 10 percent of the source material! Yet 128kbps is considered an acceptable format in many cases.

For my ears mp3 audio, while still acceptable, has less depth and definition than uncompressed audio.

On the subject of lossless file formats, I’m aware of the opinions of some audiophiles(of which I am not one)that they can hear subtle differences in file types that they attribute to the actual coding of the file format(aiff, .wav, …)

#7

LAME definatly is the best mp3 encoder out there. I have encoded 128kilobit mp3’s with LAME that sound better than 160 or 192kbit mp3’s with other encoders.

Or so my audiophile friends tell me. I personally can’t tell the difference between a decently encoded mp3 and a CD, even on fairly high end equipment.

#8

I don’t believe this is correct. A compression ratio of 7.4 doesn’t mean that 7.4 bits are discarded for everyone one kept, because MP3 is a combination of lossy and lossless compression methods. After the music signal is quantized and filtered, it is Huffman encoded. That last process is a final compression step that is lossless.

#9

A compression ratio of X means the file size (or bit rate) is being divided by X. Quite simple really.

#10

Then they probably are delusional. AIFF, WAV and AU formats only refer to how the file is structured. In other words, mostly how the non-audio data is formated. AIFF only supports uncompressed audio, WAV and AU on the other hand support some forms of data compression.

From a sound quality point of view, what really matters is the format of the audio data itself. If you have PCM data at 16-bits, 44.1 kHz, it doesn’t matter what kind of package you put it into. The same data bits are going to get sent to the DA converter.

Now, of course, not all uncompressed audio is equal. “CD quality” means 16-bit PCM at 44.1 kHz. This is not going to sound the same as a 24-bit PCM at 96 kHz, or 8-bit PCM at 22 kHz.

I’ve read very heated exchanges on music-tech mailing lists about how various playback softwares affect the sound quality of a PCM soundfile. The culprit in (supposed) reduction of quality would be rounding errors introduced by volume adjustment multiplications. Some claim they can hear the difference, some claim that’s impossible.

#11
      • MP3’s support various file bit-rates, (I think) 56Kb, 64Kb, 96Kb, 128Kb, 160Kb, 192Kb, 256Kb and 320Kb/sec.
  • 128Kb/sec is the “default” rate that many programs use, but for constant-rate MP3’s, high-frequencies such as cymbals sound warbled at that rate. I have read that average listeners on typical low-end stereo equipment can’t reliably tell a 192Kb/sec MP3 from the original CD being played.
  • If the guy made an MP3 rip of an audio CD of an MP3 rip of an audio CD, it’s going to sound worse. Every time you convert from higher-bitrate to lower you lose some quality.
  • The funniest part is how many who claim to be able to hear such differences refuse to any comparison-tests, on the grounds that they are simply certain that they would know if their CD player was dropping a bit here and there…
    :rolleyes:
  • They also argue about the best lossless format to rip CD’s to, but MP3 is still the most practical (IMO), just because the most programs support it and read the ID3 tags used in it…
    ~
#12

I recorded some LPs onto my PC, sampled at 44khz 16bit stereo and converted them to MP3 - the least bitrate I could stand was 256bit, any less sounded bad.