Re: [linux-audio-dev] Audio synchronization, MIDI API

Steve Harris wrote: Of course sample skipping/duplucation sounds terrible if the resampling factor is large (eg 1.2, 1.5 etc). But we are talking of a samplerate delta of 2-3 samples. If you add a sample or skip one each half second or so I think it's impossible to hear. For example (let's take the -1.0 to +1.0 range): if you have 1.0 , 1.0 , 1.0 , 0.8 , 0.8 and you duplicate sample 3 you get 1.0 , 1.0 1.0 , 1.0 , 0.8 , 0.8 which is still the same shape as the original only stretched in time a bit ( by 1/44100 = by 0.002267 %). Perhaps skipping is a bit more problematic when applied to high frequency content, basically if the period of the frequency is covered by at least 3 points then removing one will not do much damage (we remove only one point one each half second). When you get near to the nyquist frequency it's perhaps more problematic because if you incur in a case where you have 1.0 , -1.0 , 1.0 , -1.0 and you skip sample 2 you get 1.0 , 1.0 , -1.0 which would cause one period of the wave to disappear but since it's duration is limited to 1 sample and the sample deltas are high I think it's impossible to hear. If you are worried you could do an one time interpolation (not always interpolate the whole stream) but only the points where you insert/skip samples. For example in the above case if we skip sample 2 we would set sample 3 of the new stream to (sample2 + sample3)/2 = (-1.0 + 1.0)/2 = 0.0 so you gett 1.0 , 0.0, -1.0 still not the original shape but the transition from 1.0 to -1.0 is smoothed so there are no hard jumps which could cause audible artifacts. Interesting, any online pointers ? Fons what's your take on the sample skipping/duplicating ? cheers, Benno http://www.linuxsampler.org