R B-J, Steffan, Xue, Igor, Thank you all for your expert help. I meant to research all of the options you've raised (Grain (Lent's) vs Wavetable Synthesis) before responding but I also wanted to let you know in a timely manner that I appreciate your input. It's obvious now that with the wealth of info available, it'll be a while before I can post a meaningful response.
I did have a couple follow up questions that I hope aren't too irrelevant. Because we are working with the VST spec (and temporarily within an implementation of the Java MIDI Interface) we will have access to all MIDI information. Assuming the instruments are carefully tuned, I think they should be very close to the equal temperament pitch. Considering that we will have the pitch detected ahead of time (the fundamental, at least) could we reduce latency? I should clarify that we won't have access to the instrument's (synth's) implementation but will only have the output buffer information. We had used R B-J's wavetable interpolation idea when adjusting the SF2 output but I'm not sure how it would be possible when our information is the MIDI event and audio signal. Finally, worth mentioning is that the specific use is fine tuning equal temperament to just intonation so we are adjusting by ~40 cents max but mostly ~10 cents. With the goal being beatless harmony, we want precision to 2 cents because the threshold of pitch perception is right around there. 1 cent would be even better. Maybe 0.5 is too ambitious. Xue has a good point but if we disregard accuracy and trust that the synth is carefully tuned, shouldn't this be possible, theoretically? Again, thank you all for the thoughtful information. Regards, Dylan ________________________________________ From: music-dsp-boun...@music.columbia.edu [music-dsp-boun...@music.columbia.edu] on behalf of robert bristow-johnson [r...@audioimagination.com] Sent: Tuesday, August 02, 2011 1:17 PM To: A discussion list for music-related DSP Subject: Re: [music-dsp] Precise, Real Time Pitch Shift with Formant Control On 8/2/11 2:04 PM, Steffan Diedrichsen wrote: > Since you implement for a synthesizer, you may look into the option for an > off-line pitch detection and real-time grain-synthesis. Grain synthesis has a > nice formant control and is fairly easy to implement. i think that this "grain synthesis" is essentially what Lent's alg is. with enough delay, it can be done real-time, but for a synth, i wouldn't recommend doing that. in fact, for a synth, if you can do the analysis and processing off-line, you can accomplish the same effect with wavetable synthesis but the waveforms for different regions of pitch have to be sorta mixed (or interpolated on a sample-by-sample basis between adjacent wavetables). of course, if you don't do this (and just pitch up the wavetable from a single analyzed note) you'll get Alvin the Chipmunk (or Satan when downshifting). -- r b-j r...@audioimagination.com "Imagination is more important than knowledge." -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
