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LAME 3.93.1 vs 3.90.3
ye110man
post May 11 2003, 11:51
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LAME 3.93.1 using --preset standard -Z: 6,563,619 bytes
LAME 3.90.3 using --alt-preset standard (-Z is default): 6,775,038 bytes

why? is there a quality difference?
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amano
post May 15 2003, 00:52
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hmm. poor amano was searching through 1 million posts, trying to find the one, he was thinking to refer to. and, of course, it wasn't Gabriel to state it and it wasn't stated as clearly as I remembered. so a big sorry to dibrom and gabriel.
the post I was referring to was from lame dev. ALeidinger, somewhen in early october ( http://www.hydrogenaudio.org/forums/index....5&t=3836&st=25& ).
I concluded from that that the developers were aware of the possibility to break the presets, but made all important changes optional to not break them. considering this post a regression in quality appeared to me (of course) possible (dramatically proven by 3.93.0) but NOT probable. sorry, if I got some things wrong.

QUOTE
...
The changes between 3.92 and the actual code are bug fixes, portability fixes, speed improvements for "non-mainstreem OS's" (as you like them to call) and also new code (substep noiseshaping and some VBR changes). The portability fixes and speed improvements for other OS's are done in a way to not affect the quality. The substep noiseshaping has to be explicitely activated. So these changes can't change the quality per definition. Can we agree on this?
Now for the bugfixes and for the VBR changes:
The VBR changes are from Robert, and Takehiro had some problems with them. Robert and Takehiro talked about the changes and fixed the problems. Reading the public parts of their discussion and reading the commit log of the changes I had the impression they also did listening tests and made sure the quality at least stayed the same. Takehiro can tell you more about this.

For the bugfixes: bugfixes are per definition improvements, even if they affect the quality in a negative way. If they affect quality in a negative way, the problem is the algorithm, not the bugfix. So if a bug results in better quality, this isn't a deterministic behavior, it may affect other input data in a negative way (this now depends on the definition of "bug", but at least the bugfixes after 3.92 are real bugs you want to have fixed). If I remember correctly, there are also fixes which result in a better portability of the generated MP3s (and these may affect the bitrate and may therefore result in a worser sounding MP3s, but even if the quality degrades, the resulting MP3 is an improvement because the bitstream is more correct). And I think this may be the reason for the higher bitrate for the fast preset.

I followed the lame-cvs list (every commit results in a mail to this list and the mail contains the files which got changed and the commit message for these files). For some of the commits I talked with the commiter about the change (mostly with Takehiro). The only problems I see at the moment is the preset fast issue.
...


This post has been edited by amano: May 15 2003, 01:19
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