LAME: different compilers producing significantly different bitstreams, Split from “LAME 3.99 is out” Options

[Alex B]

The new 32-bit lame.exe seems to work fine for me on XP Pro SP3 (I have an AMD Phenom II CPU that supports SSE2), but it produces entirely different output than LAME 3.99.3 from the previous "main" bundle. I did not expect that. As far as I can see, the change log does not indicate any further "quality tweaking".

In some cases 3.99.4 seems to produce significantly smaller VBR bitrates than 3.99.3. I tested the settings -V1, -V5 and -V8. When the source tracks were quiet and uncompressed (classical, ambient, etc) the bit rates were 3-12% smaller than before. When the source tracks were loud and compressed (hard rock, metal, etc) the bitrates were about the same as before (or just very slightly smaller).

This post has been edited by Alex B: Jan 28 2012, 16:08

[lvqcl]

It seems that the relevant changes are somewhere in quantize.c: http://lame.cvs.sourceforge.net/viewvc/lam...athrev=lame3_99

*pxmin++ = xmin; -> *pxmin++ = Max(xmin, 1e-20f); etc.

[JJZolx]

It seems that the relevant changes are somewhere in quantize.c:

I ran a test similar as that run by Alex B, except with a sampling of files from my FLAC library, and only encoded at -V2, and found similar results. Unlike Alex, I did find numerous cases where the RareWares 3.99.4 produced higher bitrate (larger) files than 3.99.3.

What I don't understand about this explanation is that in my tests your compiles of 3.99.3 and 3.99.4 produced essentially the same bitrate in the output, unlike the RareWares compiles of the same releases. And in nearly all cases the bitrates were lower than those produced by either RareWares version.

Some examples (all at -V2)

CODE

Katia Lebeque - Rhapsody in Blue.mp3
RareWares LAME 3.99.4  196 kbps
RareWares LAME 3.99.3  190 kbps
lvcql's   LAME 3.99.4  178 kbps
lvcql's   LAME 3.99.3  178 kbps

The Black Keys - Set You Free.mp3
RareWares LAME 3.99.4  186 kbps
RareWares LAME 3.99.3  202 kbps
lvcql's   LAME 3.99.4  185 kbps
lvcql's   LAME 3.99.3  185 kbps

Yngwie Malmsteen - Leviathan.mp3
RareWares LAME 3.99.4  189 kbps
RareWares LAME 3.99.3  187 kbps
lvcql's   LAME 3.99.4  185 kbps
lvcql's   LAME 3.99.3  185 kbps