MP3 versus CD quality
EveningSky
Thread Starter
#1
21st February 2009
Old 21st February 2009
  #1
Gear nut
 

Thread Starter
MP3 versus CD quality

Could some GS Forum reader, knowledgeable in MP3 compression, explain to me what bps rate MP3 would have to be before one would notice a significant difference between the original CD audio-resolution (44.1 kHz at 16b sound) and an MP3 compression.

I find this topic confusing.

To further complicate this subject for me, I have the impression that many CDs, even CDs of well known artists, are of less than optimal, and at times down right of mediocre quality. Even some newer recordings!

Equally, some MP3s sound so good, that to my ears, I perceive that I have difficulty recognizing them as an MP3 compression.

Thank you,
ES
#2
21st February 2009
Old 21st February 2009
  #2
Lives for gear
 

CD's use PCM, uncompressed audio streams .. every sample is accounted
for and the fidelity of the original 44.1/16bit recording is preserved.

MP3, on the other hand, uses several compression techniques .. the
details of which can be found here: MP3 - Wikipedia, the free encyclopedia
While it was cool at the time, the word of compression algorithms
has matured quite significantly since the advent of MP3.

Personally, I despise MP3 .. compared to something like AAC. The compression
artifacts are completely unacceptable to me. What I notice most about
MP3 is what it does the the high-end of material (like drum overheads).
It can also pre-ring and alter stereo imaging.

If I have to use MP3, I always go as far over 192kbs as I can and choose
a constant bit rate. Variable bit-rate encoders add another level of
weirdness as they attempt to determine which parts of the material
deserve more fidelity.

I can't really comment on why a bad CD sounds bad .. I can only say
that if you think something sounds really great in MP3, it will sound
way better on CD.

jeff
#3
21st February 2009
Old 21st February 2009
  #3
Gear Guru
 
theblue1's Avatar
 

Since everyone hears differently than everyone else, as well as differently on different days, and everyone's knowledge and familiarity with sounds is different, there is no one, identifiable threshold at which one can say the sound is noticeably degraded. Untrained ears, those with colds, etc, stuffed up noses and/or Eustachian tubes, etc, will have less ability to differentiate.

In general, most folks probably are not able to differentiate a well processed 256kbps mp3 from the original, on most material. To be safe, you could go to 320 kbps.

At about the 192kbps rate, many folks who've 'educated their ears' (learned to listen for small details of difference in sound) will begin to be able to pick out the still fairly subtle degradations. Maybe.

By the time we get down to 128kbps (which was kind of the de facto standard in the early days when many folks were still on dial-up) most folks with more or less normal hearing will be able to tell right away, or, if not, can quickly be 'educated' to pick out the difference.

Now... that's for an Mp3.

More 'advanced' formats like AAC, WMA, and the fancifully named, open source, Ogg Vorbis give somewhat higher quality in most folks opinon, though there are those who prefer Mp3s because of certain aspects of the sound of the advanced formats. (Some of them will use an Mp3 at a higher rate to gain the added high end definition while avoiding the peceived negative aspects of one or more of the advanced formats.)

The advantage of the advanced formats may not be all that high at the 128kbps level, though, and that's why there has been a concerted effort by many to push the rate of acceptable fidelity up to 256kbps. (A big problem is that the iTunes store initially standardized at the degraded 128 kbps level. But when Amazon and others started selling 256kbps Mp3 files with no clunky, troublesome digital rights management encoding attached, it forced Apple to finally start selling decent quality AACs through iTunes, although for a somewhat higher price.)

And, of course, many PC folks may not have an AAC-ready player unless they have iTunes, and Mac folks and iTunes users cannot play a WMA without separate (freely available) software. (There are a lot of free players that will play any and all, of course. But not everyone has them and those who've 'bought into' the iTunes paradigm often seem reluctant to stray outside of its carefully controlled environment.)
#4
22nd February 2009
Old 22nd February 2009
  #4
3 + infractions, forum membership suspended.
 

Question

WTF ?
.wav 1536kbps
.mp3 320kbps

you write like a verry messed "crazy" person...this post is insane...
....
you should try to buy the original CD, from where the .mp3 you say that sounds so good comes from, extract that CD to .wav or .wmaL and test A/B.
wav vs. mp3
same song, same source, same player, same soundcard, same room, same DAC, same headphones, same cables, same AC line, same loudspeakers, same amplifiers, etc...
...
if you think you can do a better job than the PROS actually doing records, ok do it/proove it, to cry and complain, thers the moaning zone in gearslutz.

but... if you cannot hear the difference between .mp3 and .wav with the same source and a decent playback equipment & still think you can do a better recording/mixing/mastering job than the Pros, probably you are crazy & need medical/psycological help.
Sky
#5
22nd February 2009
Old 22nd February 2009
  #5
Sky
Lives for gear
 
Sky's Avatar
Quote:
Originally Posted by theblue1 View Post
The advantage of the advanced formats may not be all that high at the 128kbps level, though, and that's why there has been a concerted effort by many to push the rate of acceptable fidelity up to 256kbps. (A big problem is that the iTunes store initially standardized at the degraded 128 kbps level. But when Amazon and others started selling 256kbps Mp3 files with no clunky, troublesome digital rights management encoding attached, it forced Apple to finally start selling decent quality AACs through iTunes, although for a somewhat higher price.)
Blue, I need to correct this part of your post, as there has been some public confusion about what really happened with Apple around the time Amazon started selling DRM-free MP3s.

On February 6, 2007, Steve Jobs published an open letter, Thoughts on Music, where he became the first to call on the entire music industry to drop digital rights management. In it he said:

"The third alternative is to abolish DRMs entirely. Imagine a world where every online store sells DRM-free music encoded in open licensable formats. In such a world, any player can play music purchased from any store, and any store can sell music which is playable on all players. This is clearly the best alternative for consumers, and Apple would embrace it in a heartbeat."

Three of the Big Four record companies answered Jobs' call by offering DRM-free songs to Amazon and others at higher bit rates, while denying the same to Apple's iTunes Music Store. Their goal was to break Apple's dominance of the online music market by essentially colluding in favor of new competitors.

In 2009, the Big Three finally relented and offered Apple the same terms that Amazon enjoyed for nearly two years, and in return Apple relaxed its strict 99-cent pricing model, giving the record companies more control over price fixing (er, I mean setting).

I think it's important for people to know the true story. Apple has not been the bad guy here. Their only "crime" was taking a big risk back in April 2003 when no one else would, by launching the iTunes Music Store and redefining how music would be purchased in the future. It gave the traditional CD-based industry the lifeline they needed to survive into the 21st century, and the jury is still out on that one.

Sky
#6
22nd February 2009
Old 22nd February 2009
  #6
Lives for gear
 

you're right Sky .. and further, we can thank Apple for breaking the "CD-only" sales
model. The labels resisted mightily by insisting that music only be purchased
CD at-a-time. The 99 cents per song took over a year to negotiate.

jeff
#7
22nd February 2009
Old 22nd February 2009
  #7
Moderator
 
narcoman's Avatar
 

you've got to compare "like for like".... some MP3s DO sound better than some CDs.... but not the same song!!

256 before it becomes hard to discern, 320 preferable.
#8
22nd February 2009
Old 22nd February 2009
  #8
Lives for gear
 

Quote:
Originally Posted by space2012 View Post
WTF ?
.wav 1536kbps
.mp3 320kbps

you write like a verry messed "crazy" person...this post is insane...
....
you should try to buy the original CD, from where the .mp3 you say that sounds so good comes from, extract that CD to .wav or .wmaL and test A/B.
wav vs. mp3
same song, same source, same player, same soundcard, same room, same DAC, same headphones, same cables, same AC line, same loudspeakers, same amplifiers, etc...
...
if you think you can do a better job than the PROS actually doing records, ok do it/proove it, to cry and complain, thers the moaning zone in gearslutz.

but... if you cannot hear the difference between .mp3 and .wav with the same source and a decent playback equipment & still think you can do a better recording/mixing/mastering job than the Pros, probably you are crazy & need medical/psycological help.

You write as a person that has no knowledge about how human hearing works with certain masking effects and all. Also you write as a person that is clueless about actuall listening tests that have been used when developing these compression methods.

What theblue1 has written in this thread is spot on.. also he is a nice guy who knows how to behave among others..


/Peter
#9
22nd February 2009
Old 22nd February 2009
  #9
Gear nut
 

Just to throw 1 more spanner in...

mp3's of the same bitrate are not even equal. unfortunately itunes built-in conversion seems to be the standard, but for me it sounds awful even at it's highest settings. both in terms of stereo image and high frequency artifacts.

However wavelab's frounhoffer option (don't ask me to spell that again) sounds far better even at 256 (high q, slow setting).

This however is in a high quality listening environment.

It has been said before, you can't put a number on it for all the above reasons.

A better question would be "how do i data compress audio without losing any quality?"
in which case look at AAC and FLAC etc.

If you must use mp3, i.e. a client has requested this format, then 1st establish the client is aware of the quality reduction, then 2nd use the highest quality algorythm at its highest quality setting and only the most critical ears (like those typing here!) will be able to complain!

Warning: a client once asked me for an mp3 (on an audio CD!) because they weren't aware any other format existed! they thought mp3 was release quality!
So do check before you throw away all those hours of work!

So I must ask; why do you wan't to use mp3?
Sky
#10
22nd February 2009
Old 22nd February 2009
  #10
Sky
Lives for gear
 
Sky's Avatar
Apple's 256 kbps AAC format is a good overall choice when considering data size versus sound quality. For me, anything above 192 Kbps AAC is acceptable, and even 128 Kbps MP3 is okay for casual background listening.

I think this all depends somewhat on the program material. Today's pop / alt / rock recordings generally play well at lower bit rates, while dynamic classical / solo /jazz recordings may not.

Sky
#11
23rd February 2009
Old 23rd February 2009
  #11
Gear addict
 

Also note that a few mp3 encoders, such as LAME, are still under development. They sound better now at the same bit rate than they used to a few years ago.

I hear no difference at/above 192kbps (converted with LAME at high quality settings). I convert to 320kbps fixed bit rate usually because the conversion is faster than VBR and memory is cheap.

For mixing etc., I use uncompressed audio only.

Since my internet connection has become reasonably fast, I use FLAC for audio file transfers whereever applicable. Some of the newer player software (foobar, and the winamps of the last 2 years or so) can play back FLAC without extra plug-ins.

Frownhover is spelled like that:

Fraunhofer
#12
23rd February 2009
Old 23rd February 2009
  #12
Lives for gear
 

I think there are a few ways to go about judging the quality of mp3 vs. CD. First is the actual audible difference which greatly depends on the listening situation. On earbuds or most headphones for that matter, on cheaper stereos, an in cars I personally can not tell the difference between a decent mp3 and a CD. On my monitors, the difference is there but surprisingly not huge. On my nicer stereo the difference is quite huge.

Another way to judge the difference in quality is from a technical standpoint, or what is actually being done to the file. Stereophile did a test on what various types of compression did to test tones here:

Stereophile: MP3 vs AAC vs FLAC vs CD

Its hard to know how these results will translate into actual listening differences, but it shows a bit of how different compressions do their job. In that test a 320kbs mp3 was surprisingly close to CD quality, at least from what I was expecting.

I personally think that what files you listen to should depend on where and how you listen to your music.
#13
23rd February 2009
Old 23rd February 2009
  #13
Gear Guru
 
theblue1's Avatar
 

Quote:
Originally Posted by Sky View Post
Blue, I need to correct this part of your post, as there has been some public confusion about what really happened with Apple around the time Amazon started selling DRM-free MP3s.

On February 6, 2007, Steve Jobs published an open letter, Thoughts on Music, where he became the first to call on the entire music industry to drop digital rights management. In it he said:

"The third alternative is to abolish DRMs entirely. Imagine a world where every online store sells DRM-free music encoded in open licensable formats. In such a world, any player can play music purchased from any store, and any store can sell music which is playable on all players. This is clearly the best alternative for consumers, and Apple would embrace it in a heartbeat."

Three of the Big Four record companies answered Jobs' call by offering DRM-free songs to Amazon and others at higher bit rates, while denying the same to Apple's iTunes Music Store. Their goal was to break Apple's dominance of the online music market by essentially colluding in favor of new competitors.

In 2009, the Big Three finally relented and offered Apple the same terms that Amazon enjoyed for nearly two years, and in return Apple relaxed its strict 99-cent pricing model, giving the record companies more control over price fixing (er, I mean setting).

I think it's important for people to know the true story. Apple has not been the bad guy here. Their only "crime" was taking a big risk back in April 2003 when no one else would, by launching the iTunes Music Store and redefining how music would be purchased in the future. It gave the traditional CD-based industry the lifeline they needed to survive into the 21st century, and the jury is still out on that one.

Sky
Thanks for the additional info, Sky. Job's piece appeared about 7 months before Amazon actually started its Mp3 sales.

But as we know, these big institutions are like aircraft carriers... they take a long time to turn around. Amazon was apparently in the planning stages before Jobs' article, as this article from late 2006 suggests:

Amazon to Sell DRM-Free MP3s? : Christopher Null : Yahoo! Tech

By spring of 2007, the industry was rife with speculation that the Amazon store would roll out in May -- Bring it on, iTunes: Amazon readying DRM-free music service - Ars Technica -- but it actually didn't go live until September.

So Apple actually got their line of non-DRM'd Mp3s out first, in May 2007.

But it certainly seems that they knew the Amazon store was coming and were moving to counter the competition.
Sky
#14
23rd February 2009
Old 23rd February 2009
  #14
Sky
Lives for gear
 
Sky's Avatar
Quote:
Originally Posted by theblue1 View Post
Thanks for the additional info, Sky. Job's piece appeared about 7 months before Amazon actually started its Mp3 sales.

But as we know, these big institutions are like aircraft carriers... they take a long time to turn around. Amazon was apparently in the planning stages before Jobs' article, as this article from late 2006 suggests:

Amazon to Sell DRM-Free MP3s? : Christopher Null : Yahoo! Tech

By spring of 2007, the industry was rife with speculation that the Amazon store would roll out in May -- Bring it on, iTunes: Amazon readying DRM-free music service - Ars Technica -- but it actually didn't go live until September.

So Apple actually got their line of non-DRM'd Mp3s out first, in May 2007.

But it certainly seems that they knew the Amazon store was coming and were moving to counter the competition.
And thanks for your followup. You're right about the aircraft carrier analogy with these large companies.

Regards,
Sky
#15
23rd February 2009
Old 23rd February 2009
  #15
Gear Guru
 
theblue1's Avatar
 

Well... I really appreciated yours...

Because, though I didn't actually say it in so many words, I was under the mistaken impression that Amazon had got their operation going first. So, sooner or later, I would have stuck my foot in that, without your correction. Certainly, it would have been easy to infer from my first post that I thought that was the case.

It's kind of like a wiki... we all keep each other accurate -- when the community dialog is working the way it 'should,' anyhow.

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