On Fri, Sep 25, 2009 at 12:06:38PM -0400, Paul Davis wrote: > in 2.X, the resampling is done with very poor quality linear > interpolation, so ardour can resample a pretty large number of tracks.
Are you sure ? I measured it today (using the manual varispeed) and got some very strange results: - large amounts of non-harmonic distortion, basically spectral lines which are 46.9Hz apart (= Fs / 1024). 1024 was also the period size. - occasionally phase jumps, usually together with a single sample going to over 1e+15. Ardour's meter on one of the test tracks went up to +300dB while playing a 2Khz sine with +2% speed change. None of this would be produced by linear interpolation. > in 3.X, there are some choices about what type of interpolation to > use. the underlying assumption here is that if the user wants ardour > to varispeed (and note that the same code is used for > scrubbing/shuttling too), then they do not care *much* about quality. > this is not "sample rate conversion" in the traditional sense - its > "resample so that we can stay in sync". Still, there's no point in using any DAW if the result is not recorded somehow and used later. So quality does matter. > If a signal is recorded > > with some speed error, and then played back with the same > > speed error the result should be the original signal. Since > > it will be resampled on playback it has to be resampled on > > record as well, in the opposite direction. > > sure. however, i have no great interest in implementing this because > from my perspective, the "errors" that occur when the timecode source > is not sample clock synced are generally *not* repeatable, and thus > attempting to support this would actually not accomplish the goal. It would. Even if the record/playback errors are not the same, the expected result depends on their ratio, even if that ratio is not unity or constant. Ciao, -- FA Io lo dico sempre: l'Italia รจ troppo stretta e lunga. _______________________________________________ Linux-audio-dev mailing list [email protected] http://lists.linuxaudio.org/mailman/listinfo/linux-audio-dev
