Greg Maxwell wrote:
> The correct solution is not to remove the -2. :) We want that because we
> know that the psy model is often too optimistic, as it really was designed
> for CBR apps, and is thus more useful for choosing how to allocate bits
> among subbands then for determining how good something actually sounds.
No, that's what VBR quality selection is for, not the -2db thingy of tot_noise.
If you want lame to lower the psy model thresholds about 2db, use -V5
instead of -V6.
> The problem is that the psy models effectiveness for VBR selection use is
> very veriable. Sometimes, it thinks there is a ton of masking when there
> really isn't. Sometimes it's right on. The linear -2dB or the like really
> isn't all that effective.
And the linear -2dB permits lame switching to 32kbits on digital silence,
when there is absolutely no energy in, forcing always to select max_bitrate.
> Perhaps we should try doing bitrate selection purely with tuned ATH only
> model, then actually encode using the real psy model. This would have a
> number of advantages. ATH will produce more predictiable results, and I
> suspect that we're less likely to get the unpleasent 'why the hell did you
> choose 32K for this *$*@$ frame?!?' situation. This also could help bring
> VBR's speed upto par with CBR, no?
I don't see any chance of speeding up VBR encoding in doing so. You would
still have the binary search to get the optimal bits needed, but for
ath only mode.
Have you had this 'why the hell did you choose 32K for this *$*@$ frame?!?'
situation in recent lame versions?!?
> I figure we can probably tune a dummy ath_model not to over estimate
> bitrate better then we can get the l3 model not to under estimate.
I'm afraid you would be always too pessimistic in doing so, or you would
introduce distortions you don't want.
I like the way VBR works now. OK it's slow, and there may be some BUGs still
in there, but it's quite useable.
Robert
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