The MP3 audio file format: Warning! Do not use for serious audio.

[A.S.]

Now that I am in the last stage of optimising the new Monitor 40.1 (provisional name) the prototypes have taken on an identity of their own, slinently awaiting my next visit to the Cottage R&D centre where I play all end every type of music on them to try and catch them out. Thus far, they're still smiling - I can't.

When auditioning speakers as a designer rather than listening to music for pleasure, I only need to listen for 30 seconds or so to track as I have in my mind an impression of how the track should sound. A brief listen is enough to compare what I hear with my mental memory - then move on to the next snippet. The objective is not to fall head over heels in love with the speakers but to retain maximum objectivity listening, as it were, to avoid the equivalent of continuous eye contact with a pretty girl across the room.

Anyway - rather than handling a pile of CDs some of which are at home, some at work and some in the Cottage I thought I'd rip the favourite torture tracks onto one CD. That was easy, but by the time I'd finished I'd enough to (unsurprisingly with hindsight) fill three CD's which I burned. As my new CD player advertises the ability to play MP3s from a data CD (not tested) I used the inbuilt converter within Nero burning program to convert a selection of files from .WAV to MP3 and burned a data CD with the MP3s.

When I arrived at the Cottage I dropped the MP3 disc into the CD player and to my slight surprise it found the folder and stated to play. Forgetting that I was playing the MP3 disc I was immediately disturbed by the sound - dirty, completely devoid of ambient detail, compressed, airless and with a narrow mono-like sound stage. I initially thought that I had damaged the system or speakers and checked everything until I belatedly recalled that I was listening to the MP3 disc. I replaced it with the .WAV disk. The difference in audio quality was immense: shocking in fact. The original .WAV files had air and detail, and the stereo huge and wide. I swapped the discs several times with the same conclusion. I had no idea that MP3 could sound so terrible.

I subsequently checked the MP3 disk in the PC. When I made the WAV to MP3 conversion I thought that I had selected 320kb (the highest bit rate for MP3 hence highest quality) and turned on Variable Bit rate so that the MP3 encoder concentrates its efforts on the hard to encode music details. It now seems that the encoder ignored my 320kb setting and these tracks are encoded at between 120 and 144kb. Also, the encoder without asking turned-on the 'joint stereo' option which seems to collapse the stereo spread.

Whether the encoder can be forced to make a .WAV to MP3 conversion at 320kb I don't know, but I can say for sure that down at 128kb MP3 is totally unacceptable as a quality audio format if you are listening on Harbeth speakers with their high resolution. If you are archiving your precious audio recordings to MP3 carefully check that the encoder is following your settings. Better still, don't use MP3 at all for quality audio.

I think that i'll investigate DVD-Audio authoring tools as this, I understand, can hold a high quality better-than-CD sound track.

[Knut Knutsler]

Quite so I think. Although I get enjoyable audio quality with acoustic instrument recordings using 256kb VBR on an ipod, they're clearly less good than than the CDs from which they are ripped. On the other hand, the few DVD audio recordings I have sound to me to be a major step up from CDs even when they are played back on a very ordinary ($150) DVD player. In fact, the step up in quality of the DVD-A over the CD seems of about the same order as the CD over the Apple 256kb VBR m4a files. Unfortunately, DVD-A can't sustain an interest in music because so little (almost nothing) is available in the format. It's not a serious format for the music lover.

[tinears02]

Hi Alan,

Thank you for sharing this, it is an interesting point. So many
people tell me MP3 sounds almost identical as wav in their systems.

And so I says to myself - now, wouldn't this be a great marketing tool for Harbeth?
"You can't hear the difference between 128k MP3 and wav in your system?
You can ..... with Harbeths " :)

[A.S.]

I have not tried the MP3 encode high bit-rate setting (such as 320kb); that was my intention but the encoder overrode my settings. Maybe or maybe not the quality would be OK at the high bit rate.

It makes me wonder how often people think that they are encoding at a high bit rate. It pays to load the disc into the computer again and read the hidden info about what has actually been encoded.

As I understand it, the clever part of the MP3 concept is the encoder. The decoders are very simple - and standard, all alike - so if you make an inappropriate setting during encoding, there is no way to salvage the situation during decoding (i.e. playback)

[0477]

With the availability of FLAC, Apple Lossless and others, there is less and less reason to use any form of lossy compression, especially as hard drive storage has become so cheap. The effects of 320 MP3 are clearly audible on a good system. When you rip from CD almost every program has the option of uncompressed WAV or AIFF and most now have some kind of lossless option. EAC is probably the most accurate ripper out there.

[A.S.]

The one plus that MP3 has in its favour is the almost certainty that in say 25 years, files recorded today in MP3 format will be replayable on future generations of audio/computer equipment. That is the consequence of MP3 being a popular format - not anything to do with its audio abilities.

I have edited the speech test of Derek and myself in the BBC anechoic chamber. It runs to many minutes which means that it has to be plublished here as a compressed file. to leave it in the original WAV format would create a huge download file. Please recommend an alternative to MP3 that I can code this test as that can meet the following criteria for our members:

1. Can be played on PC and MAC preferably in existing OS audio-player applications (QuickTime, Windows Media Player etc.) ideally without downloading any additional decoders or players

2. Is likely to be supported many years into the future so is 'future proof'

3. Free of charge to the Users (I am willing to pay for the encoder)

4. Easy or seamless to use

5. Better audio quality than MP3 at a high bit-rate.

[0477]

This is a bit of a tough nut to crack because the lossless files have been around only a few years and there is no official standard, even though they are all essentially the same. For longevity it would have to be FLAC (Free Lossless Audio Codec) which is open source and should be around forever in some implementation. Problem is, it isn't standard in many decoding programs like Quicktime. Usually you have to use a plug-in. Apple Lossless is standard in iTunes & Quicktime on both Windows and Macs so it is probably more accessible.

The good thing is that even if either format dries up, it's bit for bit accurate so you can easily transcode to something else in the future with no loss of quality. The last route is encoding using 320 MP3 using the LAME encoder which is simply the best encoding algorithm.

http://en.wikipedia.org/wiki/LAME

[A.S.]

This LAME encoder looks promising. How would it compare (remembering my previous critera) to the Apple Lossless codec? From what you say that would play without additional plug-ins in Windows and MAC.

[0477]

It's still an MP3 so not perfect but the LAME encoder seems to destroy the least of the sound. I'd run the file through and see how it sounds as well as compare the file size to Apple Lossless. So long as the file comes in at 20MB or less, either should be fine for the average person to download off the net. 20MB takes perhaps 3 minutes of a DSL or cable connection which most people have no problem waiting for.

[John Willett]

I find MP3 so horrible I can't listen to it.

It strips out the acoustic and grunges the sound.

No, I don't have an iPod or the like and will only get one when I can put 16/44.1 and 24/96 wav files on it. OK it won't be 28 million songs, just a few CDs worth - but at least it will be MUSIC ;-)

[Euler]

Alan has warned us about the MP3 format. Does the same hold for downloaded music files from iTunes? That is, does the compression used by Apple on iTunes yield music files which have audible losses, like the MP3 files? And what about the case where you copy CDs that you own onto your computer and then choose various tracks from those files to make a new CD? Is there any compression in that case?

I'm expecting a new pair of C7Es3's, and I'd like to make a couple of "audition CDs", full of tracks chosen for their ability to show off the speakers. It would be easiest to do this by downloading tracks from iTunes, but if that results in music files which are no good for serious audio, then instead I guess I would have to copy tracks from CDs I own.

Bruce

[EricW]

Alan has warned us about the MP3 format. Does the same hold for downloaded music files from iTunes? That is, does the compression used by Apple on iTunes yield music files which have audible losses, like the MP3 files? And what about the case where you copy CDs that you own onto your computer and then choose various tracks from those files to make a new CD? Is there any compression in that case?

I'm expecting a new pair of C7Es3's, and I'd like to make a couple of "audition CDs", full of tracks chosen for their ability to show off the speakers. It would be easiest to do this by downloading tracks from iTunes, but if that results in music files which are no good for serious audio, then instead I guess I would have to copy tracks from CDs I own.

Bruce

Apple does not use MP3; it uses a similar but more modern codec called AAC (suffix .m4a). The general consensus is that it is more efficient and hence higher quality than MP3; for example, a 256kbps AAC might sound about as good as a 320kpbs MP3.

Initially, music from the iTunes store was encoded at 128kbps AAC (which might have been roughly equivalent to, say 160kbps MP3). In the past year or so, they've moved the standard to 256kpbs AAC, and I think virtually everything on iTunes is now encoded at that rate (although as recently as a few months ago there were still some music encoded and being sold at 128).

To me, 128 always sounded completely awful. Flat, dull, compressed. 256 is substantially better, and might be okay for background music, the car etc. but it's not high fidelity in my opinion. I use iTunes but everything is encoded in Apple Lossless, which means I still buy CDs. As soon as Apple makes Lossless downloads available, I'll likely stop doing that.

There are some providers that provide downloads in Lossless, e.g. B&W's "Society of Sound". And in the U.S., HDTracks provides 24/96 downloads, which I'm sure sound great if you have the drive space. I think there will be more in the future - it's only a matter of time.

[EricW]

And what about the case where you copy CDs that you own onto your computer and then choose various tracks from those files to make a new CD? Is there any compression in that case?

Bruce

Not if you choose an uncompressed format to encode in. In iTunes, go to iTunes menu - Preferences - Import Settings. You will have a choice of WAV, AIFF, Apple Lossless, AAC and MP3. All but the latter two have the full information off the CD. Apple Lossless uses non-lossy compression so the file sizes are smaller, but no data is discarded - everything is still there.

Of the compressed formats, AAC is better than MP3 bit for bit, but when burning discs iTunes restricts you to the amount of music a normal CD would hold if you use AAC. However, if you use MP3, there's no such restriction. I find using MP3 at 320kpbs (VBR on), I can pack 5 or 6 albums onto one disc with quite decent quality. Not for the home system, but handy to take with you and play in the car, for example.

A nice thing about encoding losslessly is that you can then easily "transcode" - i.e. create an AAC or MP3 version of the same music at whatever bit rate you like, without affecting the original.

[johnfish]

CDP has been replaced by tis computer great interface designed by apple called -iTune . All my CD collections were rip into applelossless stored in Macbook pro. All I do was stream wirelessly to aiport -express & DIY tube buffer for sweeten before feed into my home audio amp. ...Bingo ! I can enjoy my entire music colections with no interruption. Very much like cruising in A380 first class flying non-stop SIN.-LON. :) ;)

[yeecn]

Below is lifted from Wiki: http://en.wikipedia.org/wiki/Advanced_Audio_Coding

Advanced Audio Coding (AAC) is a standardized, lossy compression and encoding scheme for digital audio. Designed to be the successor of the MP3 format, AAC generally achieves better sound quality than MP3 at similar bit rates.[1]

AAC has been standardized by ISO and IEC, as part of the MPEG-2 and MPEG-4 specifications.[2][3] The MPEG-2 standard contains several audio coding methods, including the MP3 coding scheme. AAC is able to include 48 full-bandwidth (up to 96 kHz) audio channels in one stream plus 16 low frequency effects (LFE, limited to 120 Hz) channels, up to 16 "coupling" or dialog channels, and up to 16 data streams. The quality for stereo is satisfactory to modest requirements at 96 kbit/s in joint stereo mode; however, hi-fi transparency demands data rates of at least 128kbit/s (VBR). The MPEG-2 audio tests showed that AAC meets the requirements referred to as "transparent" for the ITU at 128 kbit/s for stereo, and 320kbit/s for 5.1 audio.

So it says 128 kbit/s is regarded as being "transparent" - and I believe that statement is backed by extensive ABX testing. For me - I have found 320kbit/s MP3 completely satisfying, so I am quite sure that 256 kbit/s (maybe even 125kbit/s) AAC is good enough for me

Anyway - with the drastic decrease in price in solid state memory, even entry level mp3 players comes with 2GB RAM. Few people cares to encode down to the lowly 128kbit/s anymore.

For that matter, FLAC (lossless) is able to compress down to an equivalent of 500-600kbit/s. A full length CD can be packed down to 250MB. I have not found any reason to deal with MP3 - except for downloaded materials.

Below is a useful utility for cross-conversion to/from some 20 lossy/lossless encodings:
http://xrecode.com. You can use the program for free with a nag screen.

[steve]

FLAC format compresses but does not lose data. It is wide spread and you can convert from FLAC back to your original WAV anytime you like, With disk space being cheap and memory getting cheaper this is the way to go,

[yeecn]

FLAC format compresses but does not lose data. It is wide spread and you can convert from FLAC back to your original WAV anytime you like, With disk space being cheap and memory getting cheaper this is the way to go,

Yes - FLAC is my choice of storage for music. One problem is that almost none of the "MP3" players plays FLAC. In contrast mp3 is ubiquitous - I got it in my mini-combo, mp3 player, car player, DVD player, Western Digital Media Player and PC. Whereas FLAC is only available on my PC and my Western Digital Media Player. It is OK for me now, but I do hope that FLAC (or one of the lossless compression codec) will become more widely supported in the future.

[A.S.]

When I ripped (almost) my entire CD collection and gave it away, I seriously considered FLAC or Vorbis or one of these lossless encoders. I didn't even consider MP3, not even at a high bitrate. I decided in the end that I'd probably regret coding with an 'enthusiasts' coder in twenty years when it had disappeared and that I should either use MP3 (no) or retain the original WAV files, disk space being cheap.

So I ripped them all to 44k 16 bit WAV files, the same format they're on the CDs.

[george_k]

A few years ago I encoded a piece of music using 3 different formats (mp3, ogg, wma) using the highest possible settings (e.g. 320kbs). I then looked at each version of the song using spectral analysis and compared it to the original. I noted that in all three cases information was missing and in some cases it was quite drastic.

I now encode exclusively to FLAC using XLD on my Mac.

[kittykat]

hasnt cheap storage negated the need for compression? you can fit 600 uncompressed cds onto a 500gb pocket size drive. all for less than 150 USD's.