[M4IF Technotes] Suggest some MPEG 4 Encoders

Wed Jun 19 21:11:27 EDT 2002

Hi Stephen,
I can't argue with your perceptions of what
you've encoded, particularly if you are going
as far as doing your own double-blind tests.
However, I should point out that in MPEG's
verification tests of AAC, AAC at 128 kbps stereo
met the European Broadcast Union's definition of
"indistinguishable quality", and in fact was
statistically indistinguishable from the original
in 8 of 10 critical listening examples.
This was an extremely rigorous double-blind test, with
top-quality studio sound equipment, controlled-geometry
listening rooms, expert golden-ears listeners, and the
most critical stimuli MPEG could collect.  An independent
replication subsequently published in J. Audio Eng. Soc.
(Feb 2000, IIRC) found the same.
I must wonder if there are issues with the encoder you're
using.  From my perspective (I was the statistical
analyst on the MPEG verification test) properly-encoded
AAC should not contain audible artefacts for any normal
(non-pathological) signal in any normal listening
environment.
The listening test report is in MPEG document w2006, found
at http://www.tnt.uni-hannover.de/project/mpeg/audio/public/w2006.html
Best,
 -- Eric
----
Eric D. Scheirer, Ph.D.
edsmedia   alum.mit.edu
+1 617 666 8905
http://sound.media.mit.edu/~eds
----- Original Message -----
From: "Stephen McGrath" <stephen.mcgrath   parthus.com>
To: "Ben Waggoner" <ben   interframemedia.com>
Cc: <technotes   lists.m4if.org>
Sent: Wednesday, June 19, 2023 12:35 PM
Subject: Re: [M4IF Technotes] Suggest some MPEG 4 Encoders
> Hello, everyone.
>
> I beg to differ on the statements made here about lossy codec quality,
> particularly about AAC at 128k. Subject to the usual provisos about what
> you are looking for, quality of playback system, etc. etc., there is
> definitely a noticeable difference between source and AAC at 128 or even
> 256.
>
> Please remember we are talking about audiophile quality here - this was
> the context of the original question. For mass market consumption,
> listening over a mass market PC soundcard with cheap speakers, etc. -
> sure, the output is indistinguishable. But if you invest in a good audio
> playback system, then there is absolutely a noticeable difference. I am
> not claiming that everyone will hear it, but I am claiming that trained
> listeners and/or audiophiles will. "Trained listener" here does not
> necessarily mean someone who does this professionally, just someone who
> has listened often enough that they come to realize what they are
> hearing and recognize the distortions.
>
> Which is fine, there is nothing wrong with this. This is why there is a
> much larger market for $400 bookshelf audio systems than for audiophile
> gear. To each his needs. Just don't claim there is no difference!
>
> I can personally back this from 15 years of working in speech and audio
> compression, and much longer being an audiophile (which appears to be an
> incurable disease!) And yes, I have done this through double-blind
> testing. Many times. Repeatably. :-)
>
> Stephen
>
> Ben Waggoner wrote:
> >
> > on 6/18/02 11:46 AM, Jay W. McGuire at PigsOnTheWing   mac.com wrote:
> >
> > > I'm an audiophile and am planning to buy Apple's new Xserve w/480GB of
file
> > > space to store all of my CD audio files. Can anyone tell me if there's
any
> > > advantage, besides reclaiming additional storage space, to going with
AAC
> > > over WAV files? I'm interested in the best possible sound quality and
have
> > > been using Monkey's Audio (lossless) on the PC but, so far, there is
no
> > > support for APE files on the Mac. I listen to music constantly and am
also
> > > concerned about what kind of stress that puts on a computer. Since AAC
files
> > > would be much smaller than WAVs or APEs, will they result in less
stress
> > > (thru less frequent/smaller reads?) on my hard drives?
> >
> >     AAC can deliver great quality, but it isn't a lossless codec.  I
suppose
> > lower data rates would mean slightly less drive wear, but probably not
> > enough to fret over.
> >     Myself, my jukebox is 130 GB of 320 Kbps MP3 files, which is
overkill. I
> > probably would have gone with lossless, except the integration and ease
of
> > use of iTunes is just so phenomenal.
> >
> > > I'm playing around with QuickTime 6 right now and have made a couple
of AAC
> > > files. I'm a bit confused as to what kind of settings I should be
using,
> > > though. Like I said, I want the best possible sound quality, so does
that
> > > mean I should be encoding at 256kbits/second (the highest QT6 will
go)?
> > > Also, do I want to select any of the streaming options? I'd be
accessing the
> > > Xserve's AAC files from one or more Macs located around the house, but
> > > that's not streaming, right? And what about the setting for 'ISMA'
> > > compatibility? Do I want/need that if I'm not streaming? And what
about
> > > "tags?" Any attempts I make to enter "Artist," "Album," "Full Name,"
> > > "Copyright," "Track," etc., result in only the "Copyright" information
being
> > > kept after the file is saved. Is this a limitation of the "Public
Preview"
> > > for QuickTime 6? Or are these things not supported in an AAC file?
> >
> >     Beyond 128 Kbps, you are very unlikely to be able to tell the
difference
> > between source and output with AAC (like 256 Kbps MP3).  I encoder
higher
> > because I use my archive as a master to converting to other formats, so
even
> > imperceptible errors can cause generation loss, which I want to
minimize.
> >
> > > Who's code is being used by QT6? I think I read somewhere that it was
from
> > > Dolby? Is this true? Is any one implementation better than another? I
hear a
> > > lot of talk about a "Psytel" encoder on the PC. Is its AAC encoding
any
> > > better or worse than QT6's AAC? I tried to play the Psytel demos on
the
> > > author's site with QT6...all I got was silence. Are there
compatibility
> > > problems when going from one encoder to another?
> >
> >     Dolby is a principle creator of AAC.  Apple may very well have
licensed
> > it from them.  I don't know that there is a significant difference in
AAC
> > encoders from different vendors, like there used to be with MP3.
> >
> > > I used LAME at its highest 320k setting to create MP3s before I
decided to
> > > store uncompressed WAVs and/or use the lossless Monkey's Audio
compressor
> > > for best possible sound quality. Will I be happy with the quality of
AAC? Is
> > > it really as good as they say?  Or should I stick with WAVs or wait
until
> > > someone comes up with a Monkey's Audio decoder/player for the Mac?
> >
> >     You'll need to do some tests yourself to see what your preferences
are.
> > I'd think high bitrate AAC should be just fine for listening.
> >
> >     My hope is that .MP4 AAC audio files will eventually displace MP3.
> >
> > Ben Waggoner <http://www.benwaggoner.com>
> > Compressed Video Consulting, Training, and Encoding
> >
> > Cleaner Tutorial:   http://www.saferseas.com/navseries/adclean.html
> > My Book:            http://www.benwaggoner.com/books.htm
> > Compression Books:  http://www.benwaggoner.com/bookshelf.htm
> >
> > Compression classes at Stanford, July 15-19 and August 12-16:
> > http://www.digitalmediaacademy.org/courses/videocompress.html
> >
> > _______________________________________________
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>
> --
> Stephen McGrath                              phone: +353-1-402-5884
> Technical Director                          mobile: +353-87-2274612
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