[vorbis] APPLAUD.WAV problems

[Ed Sweetman]

On Sun, 2002-02-17 at 18:11, Michael Smith wrote:
> 
> >> > The reason applaud.wav is a problem (if it is at all anyway) is that
> >> > there is an upper and/or lower bound bitrate setting for quality modes
> >> > for vbr encoding
> >> 
> >> This is not true, the encoder does no such thing.
> >Yes it is, you should run some actual tests and see for yourself. 
> 
> Gian-Carlo was stating a fact, not an opinion. Both he and I have
> read the code - we _KNOW_ what it does, so we can state that the encoder
> does not do that - nor, with rc3, does it have the capability to (rc4
> will be able to, though it won't by default).

That's why I said it's probably done by effect and not actual straight
forward coding it in.  

<p> 
> >
> >
> >> Moreover, the problem is that the encoder is not aware that it is 
> >> creating artifacts, so it will not use a higher bitrate because it 
> >> does not realize something is wrong, i.e. it's psymodel is not
> >> perfect (this also pretty much invalidates your entire mail)
> >> 
> >> -- 
> >> GCP
> >
> >before you go throwing the entire mail away I would suggest encoding
> >absolute silence.  It's fun, especially when you get about the same
> >bitrate as the cd audio clips you're encoding at the same quality
> >level.  The evidence seems to be pointing at a lower bound being set by
> >the quality level and a detailed look at every single block shows that
> >there's a mysterious lack of bitrates below around the 128kbit range in
> >ogg files encoded at -q 5  Now you might be quick to jump and say, well
> >you need at least that to keep the stereo lossless and I really have no
> >evidence to counter that. But then I'd be quick to show you that -q 4.99
> >exibits the same exact behavior as only the lower bound bitrate is a bit
> >lower, around the 112kbit range.  
> 
> Absolute silence encodes (always) at around 600 bps (_bits_ per second.
> i.e. under 1 kbps). 
> For sections with complex content (not neccesarily very complex, but
> not silent, and not absolutely trivial), the bitrate will typically
> be fairly close to the average
the average should depend on the complexity of the clip, the -q setting
should not be setting an abr. I thought we got rid of that abr crap for
real vbr.  Now assuming there is some low inaudible noise in a silent
clip, the encoder should be stripping out inaudible information anyway. 
Again we come to a problem with the psychoacoustic engine again I
guess.  If things are really that bad then that could explain why
nothing is getting under certain bitrates at certain quality levels.  

 - that's just how the encoder works.
> I wonder how you inspected the bitrate per block? None of the tools
> or players I've seen will tell you that. (well, tools I and other
> developers have written to test various things, but not widespread
> tools that non-developers would have).

I write my own tools.  I'm not that helpless.  I just dont know
acoustics well enough to play with the psychoacoustic engine and actual
routines dealing with the source audio.  Dealing with the ogg is easy
enough.  

<p>> Whilst some of your arguments have some limited value, your conclusions
> are simply completely wrong.

can you explain why there are no low bitrates for audio sections that
require very little information to be encoded to have the quality that
is designated. 

<p> 
> Michael

<p><p>--- >8 ----
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