[MP3 ENCODER] var bitrate quality

[Francois du Toit]

Is the variable bitrate quality in any way not as 
good as constant bitrate?
Fraunhofer's new encoder only encodes var bitrates 
in fast mode. 

Re: [MP3 ENCODER] var bitrate quality

[Mark Taylor]

 From: "Francois du Toit" [EMAIL PROTECTED]
 Date: Wed, 27 Oct 1999 16:24:23 +0200
 
 Is the variable bitrate quality in any way not as good as constant bitrate?
 Fraunhofer's new encoder only encodes var bitrates in fast mode. 
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Is the variable bitrate quality in any way not as good as constant =
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Fraunhofer's new encoder only encodes var bitrates in fast mode.=20

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As a replacement for the bitreservoir, I think VBR does pretty well.
That is: encode all frames at 112kbs, except when needed allow the
bits to be increased above 112kbs.  At fixed bitrates, MP3 encoders
will try to do this by using the bitreservoir, but it will not work if
the bit reservoir runs out as it often does.  Note that at fixed 128kbs,
the average frame is about 112kbs, and the extra bits are added to
the bit reservoir to build it up.  

The more common use of VBR is for maximum compression at a given quality.
But this requires a *very* good psy-model, since the LAME VBR can
now shape the noise to almost exactly match the output of the
psy-model. Flaws in the psy-model then become very noticable.  
I wouldn't recommend using LAME in this mode just yet.  We are
making almost weekly improvments though, so maybe we will get
there.  

Mark
















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Re: [MP3 ENCODER] var bitrate quality

[Russell Davis]

 The more common use of VBR is for maximum compression at a given quality.
 But this requires a *very* good psy-model, since the LAME VBR can
 now shape the noise to almost exactly match the output of the
 psy-model. Flaws in the psy-model then become very noticable.
 I wouldn't recommend using LAME in this mode just yet.  We are
 making almost weekly improvments though, so maybe we will get
 there.

Thanks for the info, Mark, this is very helpful. My question now would be:
how would you rate the psy model of the newest Xing and Fraunhofer encoders
in VBR mode? Would you use VBR or CBR with those encoders? (Assuming quality
is the number 1 issue). And along those same lines: at this point, what
would you recommend as the best encoder for getting the best quality at a
bitrate (or avg. bitrate using VBR) of 192 kbps or less?

Thanks,
Russell Davis

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