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Why is MPC perceived to be the best?, (an off-topic audio encoding discussion)
ScorLibran
post Feb 8 2004, 18:43
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This is a question that has floated through my mind for most of a year, but only yesterday became more clear to me.

Actually, it's a two-part question...

... 1. Is MPC commonly accepted among the HA community as the best psychoacoustic encoding format? (i.e., the most efficient at achieving perceptual transparency.)

... 2. If so, why?

The first item I've heard stated quite frequently, but have never seen any results of "transparency threshold tests" that would reveal the superior efficiency of MPC. I've heard that MPC uses superior encoding technology, but I'm referring more to the end result of such development efforts...the perceived sound quality, as measured against other codecs at the point of perceptual transparency for a significant number of people.

These concerns on my part were born from a post I made here, where the points of MPC statistically tying other formats at 128kbps, but no other known test results existing, were brought up. The thread portion ended up in the recycle bin, but I'm taking the chance that my concerns about calling MPC "the best" weren't the reason it was put there.

Hence, I want to bring up this idea in a different context in the off-topic forum (in the hope that this will be the correct area for it).

What I'd like to see, for instance, for the education of myself and others, would be a results summary like the following (though this is a very simplistic example)...

Format............Perceptual Transparency Threshold (nominal bitrate across samples tested)
MPC.................nnn kbps
AAC.................nnn kbps
Vorbis..............nnn kbps

...and so forth

Granted, VBR is more efficient at mid-bitrates and up, and quality-based VBR modes aren't bitrate centric, but we need some means of measurement and comparison between codecs in this context, so if not calling it "nominal bitrate", then perhaps "average filesize per minute of audio across all samples"

Perceptual Transparency Threshold could have a fixed target, like >90% samples with 5.0 subjective ratings, and non-differentiable from reference with ABX testing.

This kind of test has been discussed before, and has been mostly viewed as having little "real-world value". And I agree. Roberto's tests are much more relevant for most music listeners, and for determining the best formats for useful purposes like streaming audio, portable players, etc.

Many of us (including me) have trouble testing even these bitrate ranges, so higher ones would be even more tedious, and would answer not as many pressing questions.

My point, though, is how can MPC be called "the best for achieving transparency" without a test such as this? (Because so far it's been shown to be only "among the best" at lower rates.)
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ScorLibran
post Feb 8 2004, 22:52
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Thanks for the input, guys. smile.gif

If nothing "formal" was ever done, I'd still like to see some kind of initiative to provide evidence that "MPC is the best" if it's going to claimed as such. I would think a variety of samples, most problem samples, and few that were not previously considered "problem samples", might provide a fairly thorough test package, without being too unmanageable. Granted, there's no way to provide a comprehensive, "across the board" appraisal of the formats (as there never is), but testing 10 samples across a variety of music styles at near-transparent encoding rates could at least provide something to point to and say "MPC is transparent at lower encoding rates than the other formats with these samples to the ears of the people who tested them", for instance.

And different people have different transparency thresholds, certainly. So like with any other listening test, the statistical validity of the results would depend on the number of testers providing results. The problem is finding people willing to listen to samples encoded at close to the edge of transparency and try to pick them out from the references with any consistency.

Special baselines would have to be set for interpreting test results, a little different than previous tests, I would think. For instance, "the threshold of perceptual transparency for a tester will be at the 90th percentile". Interpreting results by starting at the low anchor and putting results in order by increasing encode rates in each format. When a tester cannot differentiate 9 out of 10 samples, then you've found their threshold for that format. Repeat for each tester.

Then you average these threshold points across all testers, and you'd get a number (with an error margin) for each format. Throw them into a table to show which one wins (or how many tie for the "win" based on error margin overlaps).

Now, we're talking a minimum of 10 samples, let's say 5 codecs (LAME, QT-AAC, MPC, Vorbis, and WMA Pro), and at least 4 encoding rates (quality settings) for each format (perhaps targeting kilobitrates of 128, 144, 160 and 192).

10 samples x 5 formats x 4 rates = 200 test groups. ohmy.gif

Now it's unmanageable. ph34r.gif

The alternative to this kind of (likely unpopular) test, in my opinion, is that no one can say that "MPC is better". Because based on current evidence, AAC, MPC, Vorbis and WMA Pro are equally good at sub-transparent rates, and there has yet be evidence I've seen of which format wins in the range of perceptual transparency.

Unless someone can think of a way to provide evidence another way?

This post has been edited by ScorLibran: Feb 8 2004, 22:53
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Posts in this topic
- ScorLibran   Why is MPC perceived to be the best?   Feb 8 2004, 18:43
- - sthayashi   1) The answer appears to be yes. 2) This result ca...   Feb 8 2004, 19:53
- - Canar   There's never been a hard and fast test as to ...   Feb 8 2004, 21:51
- - ScorLibran   Thanks for the input, guys. If nothing "f...   Feb 8 2004, 22:52
- - Canar   The smartest way to do it would be to encode the p...   Feb 8 2004, 23:13
- - ddrawley   The proof of MPC quality is neither vague nor simp...   Feb 9 2004, 03:38
- - Eli   Its more than the quality of the codec that draws ...   Feb 9 2004, 03:45
- - rjamorim   QUOTE (ScorLibran @ Feb 8 2004, 07:52 PM)If n...   Feb 9 2004, 04:07
- - indybrett   This is what I would like to see compared. It woul...   Feb 9 2004, 05:09
- - ScorLibran   QUOTE (rjamorim @ Feb 8 2004, 10:07 PM)QUOTE ...   Feb 9 2004, 07:36
- - Kalamity   Looks like double-nested QUOTES puts the auto-quot...   Feb 9 2004, 09:00
- - 2Bdecided   Just how many people are going to give you anythin...   Feb 9 2004, 12:51
- - Der_Iltis   Is there any site you would suggest where i can fi...   Feb 9 2004, 17:04
- - bubka   QUOTE (indybrett @ Feb 8 2004, 11:09 PM)This ...   Feb 9 2004, 17:08
- - sthayashi   QUOTE (ScorLibran @ Feb 9 2004, 01:36 AM)How ...   Feb 9 2004, 17:47
- - music_man_mpc   This problem has bothered me as well in the past. ...   Feb 9 2004, 21:30
- - MGuti   if all the samples were problem samples, this woul...   Feb 9 2004, 22:00
- - ChristianHJW   To make this test sensible, you have to remove the...   Feb 9 2004, 22:03
- - Continuum   Some remarks: I think neither MP3 nor Vorbis is a...   Feb 9 2004, 22:08
- - music_man_mpc   QUOTE (Continuum @ Feb 9 2004, 01:08 PM)QUOTE...   Feb 9 2004, 22:19
- - Kalamity   QUOTE (music_man_mpc)We should start making some p...   Feb 10 2004, 00:07
- - music_man_mpc   QUOTE (Kalamity @ Feb 9 2004, 03:07 PM)QUOTE ...   Feb 10 2004, 01:16
- - Kalamity   QUOTE (music_man_mpc)I agree with you in terms of ...   Feb 10 2004, 01:52
- - ScorLibran   QUOTE (Kalamity @ Feb 9 2004, 03:00 AM)Some o...   Feb 10 2004, 02:08
- - music_man_mpc   QUOTE (Kalamity @ Feb 9 2004, 04:52 PM)QUOTE ...   Feb 10 2004, 02:18
- - ScorLibran   QUOTE (Kalamity @ Feb 9 2004, 07:52 PM)I do n...   Feb 10 2004, 02:30
- - Doctor   For narrowing down quality settings use binary sea...   Feb 10 2004, 02:43
- - Kalamity   QUOTE (ScorLibran)QUOTE (Kalamity @ Feb 9 200...   Feb 10 2004, 02:59
- - Vertigo   Do we ask why god is omnipotent? He just is....sa...   Feb 10 2004, 04:00
- - rjamorim   QUOTE (Vertigo @ Feb 10 2004, 01:00 AM)Do we ...   Feb 10 2004, 04:07
- - Dologan   The god part or the MPC part?   Feb 10 2004, 04:22
- - Mr_Rabid_Teddybear   QUOTE (rjamorim @ Feb 9 2004, 07:07 PM)QUOTE ...   Feb 10 2004, 04:33
- - music_man_mpc   QUOTE (Doctor @ Feb 9 2004, 05:43 PM)For narr...   Feb 10 2004, 04:59
- - music_man_mpc   QUOTE (music_man_mpc @ Feb 9 2004, 07:59 PM)E...   Feb 10 2004, 15:43
- - Doctor   QUOTE (music_man_mpc @ Feb 10 2004, 09:43 AM)...   Feb 11 2004, 02:17
- - music_man_mpc   QUOTE (Doctor @ Feb 10 2004, 05:17 PM)Regardi...   Feb 11 2004, 04:53
- - Eli   Wouldnt a problem sample set make the most sense? ...   Feb 11 2004, 04:55
- - music_man_mpc   QUOTE (Eli @ Feb 10 2004, 07:55 PM)Wouldnt a ...   Feb 11 2004, 05:00
- - ScorLibran   Well, the time frame for this test should really b...   Feb 11 2004, 05:24
- - Kalamity   QUOTE (music_man_mpc @ Feb 10 2004, 07:53 PM)...   Feb 11 2004, 06:22
- - SometimesWarrior   Whoa, I haven't posted here in 6 months! I...   Feb 11 2004, 06:41
- - ChangFest   QUOTE Here's my point: if we're testing fo...   Feb 11 2004, 16:18
- - Eli   QUOTE (music_man_mpc @ Feb 10 2004, 11:00 PM)...   Feb 11 2004, 16:57
- - ChangFest   QUOTE However if one codec handles problem samples...   Feb 11 2004, 23:04
- - Eli   QUOTE (ChangFest @ Feb 11 2004, 05:04 PM)QUOT...   Feb 11 2004, 23:16
- - SometimesWarrior   QUOTE (Eli @ Feb 11 2004, 02:16 PM)IMHO a tes...   Feb 12 2004, 00:38
- - Doctor   Hm, I feel a flamefest waiting to happen. Before e...   Feb 12 2004, 00:59
- - Doctor   Concerning the goal of the test. It is obviously i...   Feb 12 2004, 01:10
- - Kalamity   I would not consider this thread flammable, let al...   Feb 12 2004, 05:23
- - 2Bdecided   Before spending hours discussing and thinking abou...   Feb 12 2004, 12:18
- - Continuum   QUOTE (2Bdecided @ Feb 12 2004, 12:18 PM)Cons...   Feb 12 2004, 12:40
- - 2Bdecided   QUOTE (Continuum @ Feb 12 2004, 11:40 AM)QUOT...   Feb 12 2004, 12:51
- - fanerman91   This "Really Big Codec Test" sounds exci...   Apr 18 2004, 04:18
- - ScorLibran   QUOTE (fanerman91 @ Apr 17 2004, 10:18 PM)Thi...   Apr 18 2004, 05:43
- - damiandimitri   QUOTE Consider each negative ABX result as a ...   Apr 19 2004, 12:04
- - tigre   QUOTE (damiandimitri @ Apr 19 2004, 01:04 PM)...   Apr 19 2004, 12:46


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