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VBR quality? what does it mean?

post #1 of 27
Thread Starter 
I'm using cdex + lame mp3 codec to rip my music. in the settings there is an option to choose the VBR quality. what exactly does this mean? what is "better?" 1 or 9? also, what exactly does it do? it sounds like its setting its affinity to default to a higher bitrate or lower bitrate?

what setting do you use?
post #2 of 27
VBR means Variable Bit Rate. Instead of having a bit rate set at a certain point (like 192) it starts with a basline bit rate and increases it on a frame by frame basis as needed. Basically the mp3 bit rate goes up if the music requires it.

I run EAC and LAME, using --alt-preset-standard which is a VBR switch option. I suggest you do the same, mp3s are basically (basically) transparent to the unschooled ear at that level.

For more information about this sort of thing, check out www.hydrogenaudio.org
post #3 of 27
the bit rate will increase for complex musical passages and will decrease during simpler ones. The concept is that more samples are beneficial if there is alot going on in the music but are not necessary if there aren't a lot of fast transients etc. It lets you save on file size without having as much loss in quality.
post #4 of 27
Thread Starter 
um, lol, i guess there is a small misunderstanding. i know what VBR is but i dont know what the difference is between VBR 1, 2, 3,..., 9 aka 'VBR quality.'

my intuition tells me it has to do with its affinity to use a higher bitrate than a lower one or vice versa, but which is which? does VBR 1 mean use the algorithm with an affinity for lower bitrates within the specified range and 9 mean use the algorithm with an affinity for higher bitrates or vice versa?

thanks for the feedback guys
post #5 of 27
I was wondering the same thing...
post #6 of 27
If I remember correctly CDex has a dialog box for entering command line options. Skip the rest of the controls and just enter --alt-preset-standard and things will sound wonderful.

Trust me. =)
post #7 of 27
Thread Starter 
i actually use -alt preset insane but i wanna know what the vbr quality thing is anyway. such is the student inside of me heh.
post #8 of 27
I dont see a command line anywhere....
post #9 of 27
Thread Starter 
i dont see one either but it does have a lot of the cmd line options in a drop down menu
post #10 of 27
I still don't like the concept of losing quality in lower volume portions of music... especially when there's music that never surpasses such a low volume level. I read somewhere (I've got no info to back this up) that LAME encodes optimally at a solid 256 cbr with joint stereo, anything higher doesnt make a difference. Again, I don't know why or if that's true; I can't hear the difference between the 2 though.
post #11 of 27
Quote:
Originally posted by Distroyed
I still don't like the concept of losing quality in lower volume portions of music...
The whole point of VBR, if it's done right, is to use fewer bits WITHOUT losing quality compared to CBR. i.e. it's possible to compress the original stream using fewer bits somehow, so just go ahead and do so.

Of course, since we're in the world of lossy compression here, this is a very tricky thing, and depending on the encoder, VBR may or may not change the quality. Some of the Xing and Fraunhofer codecs were famous for screwing up your sound if you used VBR, but LAME is supposed to be pretty good about it.

One key point is that with at least some compression systems/encoders, if the psymodel doesn't think it needs more than x bits at a time to represent the original waveform, then throwing more bits at it does *not* improve quality, it just wastes file space, because the encoder won't do anything in those extra bits that it wasn't already doing. Notably, the Musepack encoder (for .mpc files, the compression system I use after HydrogenAudio recommended it) currently does this sort of thing beyond some particular bitrate; the very highest "quality" settings do ABSOLUTELY NOTHING DIFFERENT than the ones just below them, except use more filesize (this statement comes from the designer/coder of .mpc). In fact those settings are only even there for parity/compatibility with other codecs and frontends reasons.

The whole point of the previous paragraph is that it is very false to assume that more bits == more quality. It might, in fact, mean that. Or it might not. It depends on the source waveform, the encoding method, and the particular implementation in the encoder.
post #12 of 27
Aroon:

VBR 0 - 3 is of a higher sound quality and larger file size than say 7 - 10. At least, that is my impression but I could be wrong. Try it out for yourself and hear the difference!
post #13 of 27
VBR = Very Bad Recording.
post #14 of 27
The whole subject seems to be agreed upon about as equally as good headphones at this place.
post #15 of 27
Your question has sort of now been answered, but to answer it more thoroughly for anyone who is interested, here is an excerpt from the lame man page:
Quote:
-q qual
0 <= qual <= 9

Bitrate is of course the main influence on quality. The higher
the bitrate, the higher the quality. But for a given bitrate,
we have a choice of algorithms to determine the best scalefac-
tors and huffman encoding (noise shaping).

# -q 0:
use slowest & best possible version of all algorithms. -q 0 and
-q 1 are slow and may not produce significantly higher quality.

-q 2:
recommended. Same as -h.

-q 5:
default value. Good speed, reasonable quality.

-q 7:
same as -f. Very fast, ok quality. Psycho acoustics are used
for pre-echo & M/S, but no noise shaping is done.

-q 9:
disables almost all algorithms including psy-model. Poor qual-
ity.
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