Slashdot Mirror
Hydrogenaudio AAC Listening Test Results
caffeine_monkey writes "Hydrogenaudio's AAC public listening test, previously posted on Slashdot, is now over and the results are in. The test compared five codecs at 128 kbps, including Psytel, Nero, Sorenson Squeeze, QuickTime, and FAAC. The winner? 'QuickTime is a clear winner, performing much better than the competition. Sorenson Squeeze, Psytel AACenc and Nero are tied, with Sorenson slightly higher than the others. Faac is clearly the worst.'"
Did you even read the blurb? Quicktime's AAC encoder won.
Well, it seems it's not comparing formats, it's comparing encoders for AAC, to find out which is the best. The "QuickTime" encoder (exactly where it comes from, or what it is doesn't seem to be mentioned) won. If you aren't interested in AAC audio though, this set of tests doesn't really interest you.
apple refer to there container format, player and codecs all as quicktime. the story should have arguably refered to it as the quicktime aac codec or possibly the apple quicktime aac codec or even the apple propriatory quicktime aac compression engine
but it just used quicktime and we all knew what it ment
**** lying is wrong even for sleeping dogs
From Apple's AAC page
Because of its exceptional performance and quality, Advanced Audio Coding (AAC) is at the core of the MPEG-4 and 3GPP specifications and is the new audio codec of choice for Internet, wireless, and digital broadcast arenas. AAC provides audio encoding that compresses much more efficiently than older formats such as MP3, yet delivers quality rivaling that of uncompressed CD audio.
AAC was developed by the MPEG group that includes Dolby, Fraunhofer (FhG), AT&T, Sony, and Nokia--companies that have also been involved in the development of audio codecs such as MP3 and AC3 (also known as Dolby Digital). The AAC codec in QuickTime 6 builds upon new, state-of-the art signal processing technology from Dolby Laboratories and brings true variable bit rate (VBR) audio encoding to QuickTime.
From Via Licensing
MPEG-4 AAC has been specified as the high-quality general audio coder for 3G wireless terminals. Apple Computer has incorporated MPEG-4 AAC into QuickTime 6 and iTunes 4, as well as the latest version of its award-winning iPod portable music player. The Digital Radio Mondiale system (the next-generation digital replacement for radio broadcasting under 30 MHZ) builds on the audio coding of MPEG-4 AAC. These exciting platforms represent the state of the art in audio coding--and Via Licensing is pleased to offer the MPEG-4 AAC Patent License Agreement.
The MPEG-4 AAC standard incorporates MPEG-2 AAC, forming the basis of the MPEG-4 audio compression technology for data rates above 32 kbps per channel. Additional tools increase the effectiveness of MPEG-2 AAC at lower bit rates, and add scalability or error resilience characteristics. These additional tools extend AAC into its MPEG-4 incarnation (ISO/IEC 14496-3, Subpart 4).
A copy of the MPEG-4 Audio standard can be purchased from the ISO online store (search for "14496-3").
Yes! Since it states as much in the article. Before asking questions, it might be good to actually read the article.
Quotefrom the article:
<blockquote>" It's important to note that the QuickTime codec used in this test is the same one used in Apple iTunes(but using a different coding mode). The samples were encoded in QuickTime's "Best" quality mode, while iTunes uses the "better" setting. This setting reportedly produces the same quality as "best" on 16-bit material. (Best is targeted at 24bit material)"</blockquote>
- Henrik
- when the Shadows descend -
AAC is not necessarily copy protected. For instance, if you encode your own music with iTunes, the files are not protected in any way.
Obviously, it would be difficult to conduct a listening test if the files in question wouldn't play on everyone's computers because of digital rights management, right?
The individual sound files for iTunes are encoded by the various record labels, not by Apple, and so could be encoded by any one of the encoders. Apple receives raw .aac files, then puts them into a DRM'ed quicktime wrapper.
In general, I believe most iTunes music is actually NOT encoded directly with the Quicktime encoder, because Quicktime for Windows didn't handle AAC encoding at the time of the launch (Only Mac Quicktime did), and most of the record labels actually use Windows for their conversions.
RTFA. This was onlyl the first step; next, HydrogenAudio will take the AAC winner (QuickTime) and compare it to what they consider the best encoders for the OGG Vorbis, WMA, MP3, etc.
The article claims the QuickTime audio format as a clear winner. Yet in most graphs the 95% confidence markers overlapped with other formats. Most statisticians would then say "Not Enough Data!!"
OK The results suggest that Quicktime was better but its not a clear winner until the 99% confidence intervals don't overlap, let alone the 95% ones. As one other poster said. You need a bigger sample size.
As for the noise being louder in the balancing amps than from the RF, that's not true necessarily - I work at a radio station, in a high-RF environment. If we don't balance, we get audio on all of our long runs of wire... including our network cables.
-T
There are three speed/quality settings in QuickTime. The first is fast and cheap, and really only meant for real-time broadcasting. For this, we're interested in "Better" and "Best" modes. The only real difference between then is when working with more than 16-bit source. Better uses every quality optimization technique that works when the source is only 16-bit. Best uses additional techniques that improve quality with higher bit sources (like 20 or 24 bit, common in audio mastering).
iTunes is tuned for CD ripping, so using "Better" mode by default is just fine.
AAC-LC can also decode at more than 16-bit in some implementations. This means it's possible to make a AAC-LC encode that is better than CD quality, if the source is more than 16-bit. I gather Apple does this with the iTunes music store, using better than CD quality masters for the encode when available.
My video compression blog
There is a whole field of science which deals with the statistics of subjective measurement. Here's a reference to a book which you might pick up to inform yourself:
Sensory Evaluation Techniques
Subjective tests of codecs are not new or particularly controversial. See the MPEG group's own subjective test of AAC:
Report On The MPEG-2 AAC Stereo Verification Tests (PDF File)
The statistics in the hydrogenaudio test treats each listener as a "block," which takes into account the fact that different listeners will have different ideas about what constitutes a "4" or a "2," etc.
The next test will use an anchor (Blade mp3 at 128 kbit/s) to keep the ratings in perspective.
ff123