Hi, Am Dienstag, 6. April 2010 21:52:41 schrieben Sie: > 1. Chose a sane but fixed output-sampling-rate (44.1 kHz, 48 kHz, 96 > kHz ... any of these will do. I would rather not go far beyond 96 > kHz... Why? Given alias-"free" generators no one even can hear > 22.05 kHz tones...) When doing post-processing of render output, samplerates up to 192 KHz IMHO can be helpful - even if most people won't need it. > 2. For "low quality" (==real-time output) I would just run everything > on that rate. Generators, filters, everything. That's whats already done, if I didn't understand you wrong. > 3. For "high quality" (==rendering output) I would just run the > generators (== Oscillators) on a /significantly/ higher rate. I > would _not_ opt for alias-free waveform-generators To be honest, there's a checkbox but currently it does not have any impact yet.. so don't let you get confused by that.. ;-)
> (BLIP or
> something alike, as these are limited to only a small subset of
> the useful operations) but for a very high sampling rate (~16x
> oversampled) and down-sample immediately after the generators via
> stacked Sinc-Filters (to make this halfway fast at least). So we
> would get virtually alias-"free" sampled output on a sane
> sampling-rate. This is what I would feed into the filters and
> effects. So their output will be the same than with the
> real-time-preview (just without the alias).
Why downsample before filters and effects? Usually you want to process audio
data at highest samplerate until the end and downsample afterwards. Exceptions
are made for LADSPA plugins that are known/were reported to go crazy with
higher samplerates.
> By doing so, I bet that most (if not all) stability problems
> ("stability" in terms of audio-quality) of lmms will be gone...
Hm.. probably true for filters but not in general. However I'm not completely
familiar with all the higher DSP math behind filters etc. so correct me if I'm
wrong.
> [*] I personally regard a stable rendering quality which as closely as
> possible resembles the real-time output (but of course without the
> alias) as being essential for the acceptance of lmms against other
> solutions, such as MusE or commercial products. Just because if one
> presses the big render-knob he/she wants to know it sounds the same ...
> just better (that is without the aliasing) than before...
Do you know how other solutions handle this issue? Do they all downsample
immediately after the generators?
Toby
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