Unless I'm mistaken, there is a problem with the standard settings that
LMS used to transcode when streaming to a bitrate limited player.
This is the string that's used, for instance, to transcode from FLAC:
[lame] --silent -q $QUALITY$ $RESAMPLE$ -v $BITRATE$
Now, the quality setting is the one we set under each player settings (0
to 9, 9 being the default that uses a fast psychoacoustic model, good
for high bitrates). The problem comes with the -v switch that is used.
That is equivalent to use -V 4, which yelds a bitrate of about 165kbps
(it varies, considering the -v settings are VBR).
This makes completely worthless the $BITRATE thing, considering it
translates to {BITRATE=-B %B}.
So, supposing I set a player to Quality 9 (the default that the
interface tells us sounds very good at high bitrates) and limit it to
320kbps... what do I get? In case of a FLAC to be transcoded I think
that the normal expectation would be to expect a 320kbps MP3 to be
streamed. But if I'm not mistaken, that's not the case. Because the
transcoding line would read like this:
lame.exe --silent -q 9 -v -B 320
This encoded a V4 variable bit rate MP3, which has an upper bitrate
limit of 320kbps. But V4 is never going to hit that limit, sitting
conveniently in its usual 165kbps range. So even though LMS is telling
the player that it's sending it a 320kbps MP3, I really don't see how
that could be the case.
Wanting to keep the same approach (otherwise I think the changes needed
would be more far reaching), the correct line to use in convert.conf
should be:
[lame] --silent -q $QUALITY$ $RESAMPLE$ -V 0 $BITRATE$
This would use the V0 preset that has a target bitrate of 245kbps
(http://wiki.hydrogenaudio.org/index.php?title=LAME#VBR_.28variable_bitrate.29_settings),
with bitrate peaks at 260kbps. Considering that the current settings go
from 256 to 320, it would still make sense to keep them as they are. 256
would strictly enforce the 256kbps limit, while 320 would let the V0
preset more space to "breathe".
I don't think that, given the currently available variables we could
have a real 320kbps CBR setting, as that would require the use of the -b
320 switch, that's not compatible with the rest of the bitrates.
All this, as I mentioned at the beginning, unless I'm mistaken and mp3
transcoding happens in a whole different way.
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