[Vorbis] bitrate limits don't work with -q settings?

[Nic Watson]

I'm sorry if this question has been asked before; I've looked through
the archives and haven't seen anything.

The problem I'm seeing is that oggenc's VBR encoding doesn't seem to pay
attention to any sort of bitrate limitation, either the -m or
bitrate_hard_min settings.  It isn't that it temporarily dips below the
minimum; the average for the whole (in this case, easily compressible)
file is 10-20% too low.

I see roughly the same results on an old 1.0.1 version of oggenc as well
as a new vorbis 1.1-linked one I found on rarewares.org.

The following works:  the final (non-VBR) bitrate exceeds the minimum 
bitrate.

$ /c/Program\ Files/ogg/oggenc -m 96  input.wav
Enabling bitrate management engine
Opening with wav module: WAV file reader
Encoding "input.wav" to
          "input.ogg"
using bitrate management (min 96 kbps, no max)
         [ 99.7%] [ 0m00s remaining] \

Done encoding file "input.ogg"

         File length:  2m 47.0s
         Elapsed time: 0m 38.0s
         Rate:         4.4175
         Average bitrate: 97.4 kb/s
--------------------
The following doesn't work:  the final average bitrate is significantly
lower than the minimum.

$ /c/Program\ Files/ogg/oggenc2 -m 96 -q 3 --managed input.wav
Enabling bitrate management engine
Opening with wav module: WAV file reader
Encoding "input.wav" to
          "input.ogg"
at quality level 3.00 using constrained VBR (min 96 kbps, no max)
         [100.0%] [ 0m00s remaining] -

Done encoding file "input.ogg"

         File length:  2m 47.0s
         Elapsed time: 0m 16.0s
         Rate:         10.4915
         Average bitrate: 92.9 kb/s
---------------------
Nor does the following work:
$ /c/Program\ Files/ogg/oggenc -m 96 --advanced-encode-option
bitrate_hard_min=96  input.wav
Enabling bitrate management engine
Opening with wav module: WAV file reader
Encoding "input.wav" to
          "input.ogg"
using bitrate management (min 96 kbps, no max)
Setting advanced encoder option "bitrate_hard_min" to 96
         [ 99.9%] [ 0m00s remaining] -

Done encoding file "input.ogg"

         File length:  2m 47.0s
         Elapsed time: 1m 54.0s
         Rate:         1.4725
         Average bitrate: 74.5 kb/s

Nic