On 12/05/2011 02:50 PM, Fons Adriaensen wrote:
On Mon, Dec 05, 2011 at 12:20:24PM +0100, Jörn Nettingsmeier wrote:
* i'm assuming you are looking at the maximum level of all channels, and
then apply the same amount of gain reduction to each of them.
Yes.
certainly
the way to go in speaker-based mixes. but as i already mentioned over
that coffee at ICSA, do you think it could be useful to add an ambisonic
mode which would apply the gain reduction only to the component that's
actually over? my hope is that the result is more subtle, because only
the source sharpness would change slightly, and with b-format, there is
no danger of irritating jumps of the source...
Actually that is not true - sources would move. Imagine a simple WXY
system. You have a source at 45 degrees and one at 90. The one at
90 (say some percussion) makes Y go into limiting. This means the
one at 45 will move forward.
right, now i see the problem..
So any gain change would have to affect equally at least all components
of the same degree. And even that can only be done for a short time,
as modifying the gain of one degree makes a complete mess of the decoding
- rE will drop sharply and rV can take on any value, even go 'negative'.
After at most a few tens of milliseconds the other components would
have to follow.
So that would require separating transient gain changes from longer
ones. This would be possible in e.g. a compressor, but for a peak
limiter (which has to ensure that no samples are over 0dB whatever
happens, and operates in feed-forward mode) it can become quite
difficult.
I tried something similar: to make transient gain changes affect only
the mid and high frequency part of the signal, but I had to abandon
that idea (at least for now) - it really gets very hairy.
Assuming it could be done, the limiter would have to know which
channels belong to the same degree. No problem if you only have
complete sets, but I want to support horizontal only and mixed
order sets as well. The plugin system in AmbMixer can handle
this. Others could mayby do it with a few more extensions, but
those would always imply explicit AMB support by the host.
thanks for elaborating. i agree, it's too hairy to be worth it, and i
dislike tools that try to be too clever - even if it could be done, i'm
sure it will confuse some users in corner cases, and the final stage of
a production is not a good place for interesting surprises...
best,
jörn
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