LAME: VBR vs. ABR

From www.mp3dev.org:
CBR/ABR/VBR: the 3 encoding modes

LAME is able to encode your music using one of its 3 encoding modes: constant bitrate (CBR), average bitrate (ABR) and variable bitrate (VBR).

Constant Bitrate (CBR)
This is the default encoding mode, and also the most basic. In this mode, the bitrate will be the same for the whole file. It means that each part of your mp3 file will be using the same number of bits. The musical passage beeing a difficult one to encode or an easy one, the encoder will use the same bitrate, so the quality of your mp3 is variable. Complex parts will be of a lower quality than the easiest ones. The main advantage is that the final files size won't change and can easily be predicted.

Average Bitrate (ABR)
In this mode, you choose the encoder will maintain an average bitrate while using higher bitrates for the parts of your music that need more bits. The result will be of higher quality than CBR encoding, and this mode is highly recommended over CBR. This encoding mode is similar to what is reffered as vbr in AAC or Liquid Audio (2 other compression technologies).

Variable bitrate (VBR)
In this mode, you choose the desired quality on a sqale from 9 (lowest quality/biggest distortion) to 0 (highest quality/lowest distortion). Then encoder tries to maintain the given quality in the whole file by choosing the optimal number of bits to spend for each part of your music. However, this mode heavily relies on the encoder psychoacoustic model and could lead to a few "bad choices" in the encoding process. You may want to specify a minimum bitrate (ex: -b 64) to avoid those potential errors.

I know that VBR is the most popular mode for LAME users right now but I wonder if ABR is better. Lots of web sites recomend ABR over VBR. Has anyone used ABR? What kind of results do you get?

Opinions are the key here. I have wondered the same thing myself. From some of the message boards I visit it is all what you prefer. ABR and VBR are both comparable to sound the key factor is drive space. But if it is stereo separation you want 256 .. stereo CBR is the way to go. Otherwise most lame supporting encoders suggest J-stereo in VBR format ABR is rarely refered too but from the songs I have done I can not tell the difference in sound only file size.

[schmooky007]

mazer:

abr is vbr, just a different "form" of it
abr sets forward the concept of "unlimited" bit reservoir.. this means that complex pieces of music that require more bits can now be coded more accurately

however, when lame 3.88 beta was released, a few people reported hearing "ringing" artifacts with popular abr settings like --abr 192, 256, etc ... from what i heard --nspsytune supposes to fix that but i haven't tried it out yet

my ideal abr command line in lame 3.89 would be
--abr 224 -b 160 -m j -q 0 --nspsytune --nssafejoint --lowpass 19.5
file size will be a little big but sound quality should be (in most cases) fairly solid

to avoid clipping, if the peaks of the original are over -0.3db (or 97%) try adding --scale .90 to .93 to the command line

besides, i'm still using cbr with both lame or producer pro, depending on me mood and whether i have patience to wait for producer pro abr is good though if you want the best sound quality vs. less disk space wasted

Originally posted by schmooky007
mazer:

abr is vbr, just a different "form" of it
abr sets forward the concept of "unlimited" bit reservoir.. this means that complex pieces of music that require more bits can now be coded more accurately

From what I understand ABR doesn't run the risk of overcompression like VBR does and it doesn't run th risk of undercompression like CBR does. My quote from mp3dev makes me think that a VBR can actually sound worse than ABR if LAME isn't set up correctly.

Does CBR really have better stereo separation, even in stereo mode?

Thanks schmooky, btw, Delerium - Silence is awesome.

[schmooky007]

both encoding modes can produce bad results if the settings do not correlate with the type of music you're trying to encode

the thing with abr is that a lot of people dont like it because it sets a specific bitrate target where the encoder does its best to keep it somewhere within that specified area. vbr with only -V doesn't. setting a maximum bitrate in vbr is obviously not recommended unless it -B 320 but u dont really need to put that in

stereo separation in mp3s depends on what stereo mode u choose and that basically has to do with the bitrate. it has nothing really to do with what encoding mode u choose, but rather what is the minimum bitrate. 192kbits and below should be encoded joint stereo. 224kbits and above should be encoded stereo. u could end up with significant artifacts if u encode stereo at too low bitrates, so for example if you're using vbr and the minimum bitrate there is 128kbits, then obviously you want to use joint stereo. joint stereo is a good technique to increase audio bandwidth at lower bitrates but it becomes kinda useless at higher bitrates. the price of joint stereo is obviously loss of stereo separation and some flange with live recordings or songs with a lot of wide stereo segments, but the good thing about it is that it increases encoding efficiency and it gives better results at lower bitrates then if you would have used true stereo instead. joint stereo with higher bitrates (i.e. 256 or 320kbits) can risk introducing artifacts too because at those bitrates you should encode stereo

remember whether you encode joint stereo or stereo in cbr mode, it doesn't affect file size in any way, only in vbr but even there the difference is not that big

hehe enjoy delerium.. :P sorry i couldn't upload the full length
its almost 12 minutes long and at 224kbits its almost 19mb

Thanks a bunch schmooky, I always learn something new here.

[schmooky007]

Originally posted by Mazer
Thanks a bunch schmooky, I always learn something new here.