Vbr

As I understand it, it lowers the encoding bitrate when the audio is either not very complex or at low levels, then raises it again for detail, etc. This can save a lot of space for speech, telecommunications, etc.
Quite an impressive technology, really. Anybody fill us in some more?
 
Sure. I have one mp3 that is encoded with a variable bit rate. It works right on about 50% of the mp3 software players I've tried. It does work on itunes. It doesn't work on my rio, and some other software players. By not work, I mean the speed of the song gets screwed up. I guess it depends if the player supports it or not.
 
Originally posted by symphonix
As I understand it, it lowers the encoding bitrate when the audio is either not very complex or at low levels, then raises it again for detail, etc. This can save a lot of space for speech, telecommunications, etc.
Quite an impressive technology, really. Anybody fill us in some more?
Click to expand...

VBR is a variable algorithum for encoding stuff. But with all mpeg encoded stuff, DVD's mp3 etc. It's actually the other way round.

If a scene in a DVD has fast moving, colour changing shots one after another. Action movie basically, then the bit rate doesn't need to be high as the eye can'e analyse that frame fast enough. But if its a slow panning shot where not much changes. ie, pan across the sky, sea or slow scene, the Bit Rate has to be a lot higher so that there's more information to 'fool' the eyes into thinking its a good picture.

Same as music, if it's loud fast changing music: korn then the bit rate doesn'y need to be high. But a quiet, soft piece of music (most classical stuff) needs to have a high bit rate so that you're eyes can't pick up on the fact that you're listening to a highly compressed file.

Try out Barbers Adagio For Strings at three different bit rates, and see if you can hear the different at the softer bits and at the intro. Then try out a hard rock, thrashy bit of music. You'll be supprised how much you can hear the difference in the classical piece but the rockier stuff is harder to hear.
 
VBR is a really nice thought. The fundamental idea is already stated, that sometimes an algorithm will be able to work really well with low bandwidth, and other times it needs more to be good. VBR is supposed to allow the algorithm to change bandwidth moment to moment as needed. In MP3's however, especially of music, it's almost worthless. It's not supported everywhere, and MP3 just doesn't work like that. future algorithms for audio may use VBR more effectively. Video codecs use it really well already.
 
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