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a response to a growing rumor...
Dibrom
post Feb 12 2002, 00:36
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Normally I wouldn't attempt to address an issue in this manner, but since it is getting a bit out of hand, and usually on boards I'm not participating in (or have little desire to participate in), I'll try and address it officially, once, in the place where it should be the most relevant.

The matter I'm discussing is related to the --alt-presets and their handling of the "stereo image".

There have been some completely unsubstantiated reports and rampant speculation going on in a few threads which I will list below:

1. http://66.96.216.160/cgi-bin/YaBB.pl?board...&num=1013124809
2. http://www.digital-inn.de/showthread.php?threadid=8212
3. http://www.hydrogenaudio.org/forums/showth...s=&threadid=759 (I simply hadn't gotten around to responding to this thread though its on this board).

At any rate, I'll try to make a few points as clearly as I can.

1. All of the --alt-preset VBR modes are tuned for "stereo image".

2. All of the vbr presets provide better sound quality via joint stereo than LAME on it's own with joint stereo, and in some cases should even sound better than with --nssafejoint, while at the same time providing a lower bitrate.

3. The --alt-presets do not, by design, make any sacrifice in regards to stereo image to keep bitrate down. Anyone who tells you this has no idea what they are talking about. I should know since I actually wrote the code and designed the presets.

4. An extremely high degree of stereo frames is not always needed to achieve good sound quality. I challenge anyone who believes that --alt-preset standard has poor stereo seperation, on a common basis (as a few unsubstantiated claims imply), to provide me with direct evidence of this.

5. Joint stereo is needed even at bitrates of 320kbps to achieve the best sound quality in some critical cases. Forcing stereo on everything up to 320kbps and then forcing joint stereo does not fix the problem (as user implies in one of those threads). I've tried this before.

6. There seems to be a misconception that all that the --alt-presets improve on are pre-echo. This is sorely mistaken. Indeed they do improve on pre-echo and impulse handling to a fairly large degree, but they also improve upon:

- joint stereo handling (serioustrouble is a prime example)
- dropout prevention (2nd_vent_clip is a prime example)
- fluttering (gekkou is a prime example)
- knocking (velvet is a prime example)
- ringing (bloodline is a prime example)
- noise pumping (piano, rach_original, etc, are examples)
- rasping (present with noise shaping 2 on some clips like fatboy, or on clean vocals sometimes. Mostly eliminated, even on the most critical samples, with --alt-presets)

And that's just the stuff I can think of off the top of my head.

Now, that's not to say the --alt-presets are perfect. I certainly know they aren't. But they also don't have some massive flaw in regards to stereo image which is present to the degree some people imply. In fact, the only case I've seen which I put any credence in is the few isolated cases which Wombat has found (and provided samples for I might add). I will eventually attempt to address these few samples, but note that these are exceptional cases, not common cases, and as far as I can tell, they are completely unrelated to the other complaints being made. This is especially so since Wombat doesn't describe the artifact as being a collapse of the stereo field (which isn't your typical joint stereo artifact in LAME anyway...).

At any rate, I'm always looking to improve things if I can, but claims must be substantiated which includes providing abx results (which are then verified by other parties) and providing test samples, preferrably multiple ones if you are implying a problem with general behavior.

Not to come across arrogant, but for the most part, I'm the only one who truly understands the workings behind the --alt-preset specific tunings. Not even the other developers have followed my work (though that's by their choice, not mine). The code is available for all to see, but so far I have not seen anyone attempt to reimplement my modifications or to discuss them with me on a technical level. So unless you see someone who is closely related to the work I've done (ie, they have participated in testing, JohnV for example) stating something, or you see me stating something directly about the presets, then chances are whoever is discussing the presets doesn't have the full picture. This is especially true when people begin discussing how the --alt-presets work internally or technically, and especially in relation to joint stereo.

If you see a discussion on another board about these issues, please point people to this thread. If you have a question, please ask me here, you'll likely get a much more correct answer in addition to helping to keep questions about this issue centralized and concise (which will help when the FAQs are created). Speculation is not only wasteful, but it also helps to propogate misinformation such as the old "joint stereo is bad" line of thinking.
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Dibrom
post Feb 12 2002, 06:03
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QUOTE
Originally posted by ff123
It's a many-headed hydra.  Just as soon as one can show that a particular individual setting is inferior to --alt-preset standard (such as -q0 -V0 -b160 --athlower 1 lowpass 20.5), another one pops up with an additional tweak ("This one gets close to or is as good as aps, which sounds 'brash' to me, maybe even better because aps uses joint-stereo, which must logically degrade the stereo image; and what's more, I didn't even try hard, just used the default settings with a couple of tweaks -- aps must be in need of improvement!").


Indeed. One of the biggest problems also is that there are no real controls in the comparisons that other people are making. For example, they are testing largely on non-critical samples (being defined as those which L.A.M.E. and other mp3 encoders are known to have problems on), not enough of these samples, not enough people are verifying their results, and I'd dare say that often there are not enough "sensitive" listeners participating. Really, all of that is pretty much an understatement..

QUOTE
[b]In one thread, I took two easy-to-hear samples, showing just two different types of artifacts on which --alt-preset standard is superior to the command line in question.  But rumors die hard -- since I didn't listen to samples which might possibly have stereo separation problems (although I am willing to upload reasonably short samples to my page -- no multi-hundred megabyte files, please), the argument goes, aps may be inferior in that regard.


Perhaps another problem is that people give to much credit to unsubstantiated claims. I'm very skeptical myself, as are some other people on this board, mainly because there have just been so many cases where the problem turned out to be non-existant, or when verification was called for, the person just disappeared. I guess I just prefer to take a "guilty till proven innocent approach" (where "guilty" is a non-existant problem), and so I naturally require proof of claims. A lot of people don't seem to take this approach though.

The bottom line that people need to realize is that there can be no fixing of a problem if it cannot be substantiated. You can't improve upon something if you don't see it's flaws. This means that if someone is complaining about something, they [b]must
provide evidence of what they are describing or it's basically useless to everyone interested in real progress.

QUOTE
[b]I think the best way to kill off inferior command lines is to test them one by one.  But perhaps there should be some record which documents each death.  And for those that refuse to die, just keep adding samples smile.gif


This actually sounds like a good idea. To go further, I've thought about compiling a package of test samples where L.A.M.E. and other MP3 encoders have trouble with, but where --alt-preset standard does very well. For each new command line someone thinks they can come up with that is superior (which really isn't possible without code modifications... but oh well), they can test against these samples. If there is a significant enough score in favor of their line (somehow taking into account quality, size, and the quality/size ratio or "efficiency") vs --alt-preset standard, then perhaps there is some merit to the other line and it warrants further investigation. This would really provide an easier way to verify the results quickly and efficiently. The list of which lines were inferior (along with release date) could then go in a FAQ of sorts.
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Posts in this topic
- Dibrom   a response to a growing rumor...   Feb 12 2002, 00:36
- - rc55   Dibrom, I'd say it'd be a good idea to keep this ...   Feb 12 2002, 00:52
- - Dibrom   QUOTE Originally posted by rc55 I'd say it'd be a...   Feb 12 2002, 01:03
- - ff123   It's a many-headed hydra. Just as soon as one can...   Feb 12 2002, 02:53
- - Dibrom   QUOTE Originally posted by ff123 It's a many-head...   Feb 12 2002, 06:03
- - mithrandir   The --alt-presets are some of the best improvement...   Feb 12 2002, 06:54
- - PatchWorKs   Well, sincerly i can't understand why LAME have so...   Feb 12 2002, 10:48
- - cadabra3   As a Psychologist (forgive me ahead of time); I se...   Feb 12 2002, 11:13
- - JohnV   QUOTE Originally posted by cadabra3 As a Psycholo...   Feb 12 2002, 13:47
- - brosselle   QUOTE Originally posted by ff123 I think the bes...   Feb 12 2002, 15:17
- - JohnV   Well, just read Roel's (r3mix's) comment about alt...   Feb 13 2002, 06:32
- - Dibrom   QUOTE Originally posted by JohnV Well, just read ...   Feb 13 2002, 08:22
- - Delirium   QUOTE [b]I've never really seen this verified, tha...   Feb 13 2002, 08:59
- - Gabriel   I think that an improvement for someone could be a...   Feb 13 2002, 09:23
- - Dibrom   Yes, nitpicking aside... it perhaps is possible (a...   Feb 13 2002, 09:40
- - cadabra3   JohnV- no disrespect intended- if you read a littl...   Feb 13 2002, 10:59
- - Pio2001   Roel didn't say he would never use APS, he was jus...   Feb 13 2002, 12:31
- - tangent   QUOTE Originally posted by Pio2001 Roel didn't sa...   Feb 13 2002, 14:08
- - JohnV   Also one thing to consider when comparing this sma...   Feb 13 2002, 16:02
- - Dibrom   QUOTE Originally posted by JohnV Also one thing t...   Feb 13 2002, 20:05
- - JohnV   Hey Dib, a bit OT. Could you make those pics a bit...   Feb 13 2002, 22:01
- - Dibrom   QUOTE Originally posted by JohnV Hey Dib, a bit O...   Feb 13 2002, 22:33
- - Gecko   That is some hard evidence, Dibrom! It may not exa...   Feb 13 2002, 23:00
- - Pio2001   QUOTE Originally posted by Gecko wonder how he ke...   Feb 13 2002, 23:16
- - Gecko   QUOTE Originally posted by Pio2001 It much easier...   Feb 13 2002, 23:47
- - Dibrom   Pio2001, It's a shame you didn't post your respon...   Feb 14 2002, 00:03
- - user   Hi, in r3mix and here people are referring to som...   Feb 14 2002, 00:45
- - JohnV   Uhm, user. About 7 messages above your post. Here...   Feb 14 2002, 01:05
- - JohnV   I'd say you really can't tell absolutely which one...   Feb 14 2002, 02:38
- - Pio2001   QUOTE Originally posted by Dibrom Pio2001, It's a...   Feb 14 2002, 13:09
- - JohnV   QUOTE Originally posted by Pio2001 To make it sho...   Feb 14 2002, 18:00
- - tangent   QUOTE Originally posted by Pio2001 To make it sh...   Feb 14 2002, 18:34
- - Gecko   Apart from discussing the point of the high cutoff...   Feb 14 2002, 19:52
- - Dibrom   QUOTE Originally posted by Pio2001 To make it sho...   Feb 14 2002, 21:01
- - fewtch   QUOTE Originally posted by tangent Really? Most o...   Feb 15 2002, 08:43
- - cd-rw.org   Just by showing up again Roel has already done mor...   Feb 15 2002, 10:28
- - Dibrom   QUOTE Originally posted by cd-rw.org Just by show...   Feb 15 2002, 11:29
- - johnicon   My $.02: I found the r3mix website in May of ...   Feb 15 2002, 13:25
- - brosselle   You know, I kind of liken this to the old vinyl LP...   Feb 15 2002, 14:46
- - fewtch   For some reason, I suspect Roel will "come around"...   Feb 15 2002, 15:28
- - user   Hi, during playing around with mp3gain, I found f...   Feb 15 2002, 23:08
- - Dibrom   QUOTE Originally posted by user 1.  maximize...   Feb 15 2002, 23:30
- - user   Thank you, now it is clear. yeah, as I spoke in s...   Feb 16 2002, 00:07


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