Head-Fi.org › Forums › Equipment Forums › Sound Science › How do you tell if a cd is actually cd quality?
New Posts  All Forums:Forum Nav:

How do you tell if a cd is actually cd quality? - Page 2

post #16 of 25
Yes, I guess it could have been misleading. I meant that if you burn a CD that´s playable in any CD-player.
post #17 of 25
Originally Posted by watchluvr4ever
I'm not sure I understand what you are saying. If I were to burn a CD in MP3 format it will take up less space.
I guess I was misleading there... I meant a CD in .cda, a "normal" CD, but made of fmp3-files.

Originally Posted by Sovelin View Post
lol, I definitely read the graph wrong. There's a very good chance I'm wrong on the 100Hz thing. It is probably closer to 50 or below. When I had my home theater system, I had the crossover on my sub set to 80Hz. When I played a song through my iPod that was at 160kbps, the bass response would be very weak. When I played the same song on the cd, the sub would knock me off my chair. I know the 160kbps is going to cut off the bass at some frequency, just not sure where.
Okay, I see then.

EDIT: Sorry for the double post, my earlier post wasn´t visible and I thought it didn´t get sended at all. Probably clicked "back" or something...
post #18 of 25
Originally Posted by TheOtus View Post
This got me very interested... How is this possible? Well, more precisely, how can a normal CD-player play that? I mean doesn´t the CD-player read the disc with a standard speed? I really don´t get this... The audio has to be compressed somehow, but how would a normal CD-player be able to get a clue of it?

To the topic, as said the analyzer or spectrum are only ways, beside listening. A CD burned of mp3-files takes the same amounf of space than a direct copy of the actual CD.
Yes. The songs will take up the same amount of space whether they come from a lossy encode or not.

As for the remastered CDs, they seem to pack the data more tightly. From Wikipedia's page on the CD:
The program area is 86.05 cm² and the length of the recordable spiral is (86.05 cm² / 1.6 µm) = 5.38 km. With a scanning speed of 1.2 m/s, the playing time is 74 minutes, or around 650 MB of data on a CD-ROM. If the disc diameter were only 115 mm, the maximum playing time would have been 68 minutes, i.e., less six minutes. A disc with data packed slightly more densely is tolerated by most players (though some old ones fail). Using a linear velocity of 1.2 m/s and a track pitch of 1.5 µm leads to a playing time of 80 minutes, or a capacity of 700 MB. Even higher capacities on non-standard discs (up to 99 minutes) are available at least as recordables, but generally the tighter the tracks are squeezed, the worse the compatibility.
post #19 of 25
Oh yes, I see. So the spiral is tighter... Well, obvious I suppose, don´t know why I didn´t think of it myself.

But, this shouldn´t reduce the quality. I got the impression that the data is compressed, not as good as normal CD?
post #20 of 25
Redbook CDs are a certain bitrate. Hence the 80 min limit on standard CDs. 700mb are taken up in 80 min. You would have a hard time proving that the file was once mp3.

Data is encoded to CD at a higher bitrate than the original. Perhaps a program could look at identical data in bits near each other, because the encoder would be reusing the lower rez bit from the mp3 to fill space in the higher rez. I doubt any program exists to do that though.

Also, I think the 160k mp3 may just be so that the downloads don't overload their server, odds aren't too bad that the CD is full quality.
post #21 of 25
Originally Posted by watchluvr4ever View Post
I'm not sure I understand what you are saying. If I were to burn a CD in MP3 format it will take up less space.

cd players that can't play mp3's can still play cd's made FROM mp3's....

say you have a cd (1411 kb/s) and you rip it LAMEly to a 128 kb/s mp3 file. when you then ask your cd burning software to burn a MUSIC cd from this file (not a data cd mind you) the software fills the bits using whatever (probably poor) algorithm to again make the file 1411 kb/s, allowing you to play the cd on any old cd player.

cd data has to fit a certain data stream standard set long ago, including (well, more like, it has the affect of having) all the music be at 1411 kb/s. that's why you can't burn an mp3 bitrate song to a cd and play it on cd players that don't support mp3.
post #22 of 25
Originally Posted by Sovelin View Post
So in this case the only thing cut out from the original song was above 15.25kHz? Well, I'm sure if we looked at it below the 1kHz mark we would see how the 160 kbps copy is lacking, probably cut off at ~100Hz
Adobe Audition using Spectral Frequency mode gives a much clearer picture. You'll notice that lower bitrates appear "blocky" in addition to the frequency being cut off at the top end and bottom end (not as early as 100Hz though).

I'll repost this later since I stupidly saved as a dirty, dirty jpg (who likes lossy compression?) and don't have more time now.

Top = FLAC
Mid = 192kbps MP3 (Latest version of LAME)
Bot = 128kbps MP3
post #23 of 25
Most of the times it's easy to detect, but you'll have to know what to search for. Even the 320kbps mp3 have this artificial noises do the compression on the very high frequencies and the very low frequencies, some times you can hear it on the mids or around the vocals too.

Any mp3 can be convert to wav, or aiff file and be burn to CD. Just keep in mind that the quality of the mp3 will not improved.
post #24 of 25
Usually, a "plot spectrum" command with Audacity should suffice: if the frequencies go up to 22500 Hz, it's an original CD.

But the reverse can be false, I've recently checked some pop music CDs in which they use mp3 samples during the recording. While the tracks went up to 22500 Hz, the cymbals on one track cut at 16 kHz (the rest of the track was normal). I suppose there are CDs that are worse, where the use of compressed samples is generalized.
post #25 of 25
to be honest. Most cd's bought today arn't even of cd quality. Philips wanted to sue a couple of music companies for applying anti cd-copying techniques which degraded the cd in such a way cd-roms could not read it any more. They opted to not get into this as the patent would expire in a year and the lawsuit would most definitely last longer.
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Sound Science
Head-Fi.org › Forums › Equipment Forums › Sound Science › How do you tell if a cd is actually cd quality?