Hello Paul (and all the others)!
> I wonder how most DAWs handle this. LMMS only performs automation
> once, before each buffer is processed.
>
uhh,...
... depending on how this is done, it may be OK (but not good, however)
or it may be absolutly unaccaptably bad...
> for pre-recorded automation (and automation track) it is theoretically
> possible to do it sample-exact, since the values are known in advance.
> For live tweaking, I dont know what to do..
>
Well, I'm not sure what you try to distinguish with this. But performing
sample-exact calculations of the audio-automation (and the envelopes) is
possible in realtime (at least on the sample-rates used for
realtime-preview and -playback), too, nowadays... So I maybe don't get
the point...
Of course you may not want to save the automation-data for every single
sample (this would be lots of data...), so usually the audomation-data
would be saved only with 100Hz to 500Hz and interpolated sample-exactly
inbetween.
Without having done further test-renderings of the output of lmms and
without having looked deeply at the source-code of these... Yes, any
block-wise calculations of volumes can be the source of a multitude of
different click-sounds. Knowledge of this fact goes back to the days of
simple audio-trackers (like soundtracker or future-composer and such
sorts of programs). These had a time-base of 50Hz or 60Hz for historic
reasons, so any sort of audio-automation (increasing the volume on every
"tick") was prone to clicks with a frequency of either 50Hz or 60Hz. To
come arround this, at least sample-exact linear volume-ramping was used
inbetween the automation-steps...
This arises some questions:
1. Is lmms doing these block-wise calculations only(!) for
audio-automation or is it utilizing this sort of calculation even
for audio-envelopes? I ask because I have these click-sounds not
only when using audio-automation but also when using just
envelopes... and sometimes even without using any of these.
2. May it be the case that for some reason uninitialized
variable-values leak into this process? I noticed some rather
strange clicks in the audio-output of at least the current master
I can't explain otherwise. They seem to be completely random and
completely unrelated to the actual audio. But they seem to happen
before the sinc-downsampler (oversampling).
3. Is there some sort of ramping used? Linear approximation or
anything better to soften the edges of the blocks?
Just to clarify this: I have these strange click-sounds not only when
using envelopes and or audio-automation. It's just that they appear to
be a lot stronger and a lot more frequent when using envelopes and or
audio-automation. These do happen so often for me, that currently I
can't use lmms for any serious production. Not even for short ones
(radio-jingles or so...). :-(
cu
Stefan
PS: I may (or may not -- depends on my other workload), set up some
simpe test-files and render these with different settings. This might or
might not give someone a clue where to look for these clicks... If so,
may I post these files (and their output, as highly compressed
OGG-files) to this list or may I use some ftp-space for it? Just asking
what would be the preferred variant?
> -Paul
>
> 2010/5/17 Louigi Verona <[email protected]>:
>
>> I have reported clicking on low values as well. Would be good if it is
>> fixed.
>>
>> I also tried doing rapid volume changes, like with an LFO, and it would also
>> generate crackling.
>> I dunno if its the same issue.
>>
>> Louigi.
>>
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>
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