Hi, It should not be circular buffer. Could you explain meanings of "fade in", "fade out", "splice in", and "splice out" ?
Thanks, Alex בתאריך יום ו׳, 15 במרץ 2019 ב-0:14 מאת robert bristow-johnson < r...@audioimagination.com>: > > > ---------------------------- Original Message ---------------------------- > Subject: [music-dsp] pitch shifting vs sample rate > From: "Alex Dashevski" <alexd...@gmail.com> > Date: Thu, March 14, 2019 2:55 pm > To: music-dsp@music.columbia.edu > -------------------------------------------------------------------------- > > > > > Let's assume we have recorder buffer(input) and playback buffer(output) > > with the same size. > > I sample input signal at 8Khz and output signal at 9Khz. > > My question is: > > Why isn't it equivalent to pitch shifting ? > > > > well, you didn't say how the samples in the playback buffer are defined. > let's say that you are simply copying the input buffer to the output > buffer. or, even simpler, let's say that the input buffer and output > buffer are coincidental, the same block of memory with two different points > writing into it and reading out of it. and let's say that these buffers > are *circular* FIFO buffers. > > so, the output pointer advances 9 samples in the same amount of time that > the input pointer advances 8 samples. that would be pitch shifting, but > you would have a click in the output every time the output pointer > overtakes and passes the input pointer. a good pitch shifter would fade > out the signal from the output pointer before it catches up to the input > pointer and would fade in the signal from another output pointer that is > farther behind. and would continue to do this. once the signal is > completely faded out, that output pointer is discarded and the fade-in > output pointer (that was farther behind) becomes the nominal output pointer > (which is still advancing 9 samples in the time the input pointer advances > 8 samples). when that gets too close behind the input pointer, we do this > again and begin cross-fading to the signal further behind. > > a better pitch shifter would make sure that the new, fade-in output > pointer is pointing to the waveform that looks similar to the fade-out > output pointer. this is what pitch detection is good for. so when extra > audio is spliced in (for up-shifting) or audio is spliced out (for > down-shifting), you want ideally that an integer number of periods of the > audio tone is spliced in or out. > > > -- > > r b-j r...@audioimagination.com > > "Imagination is more important than knowledge." > > > > > > > > _______________________________________________ > dupswapdrop: music-dsp mailing list > music-dsp@music.columbia.edu > https://lists.columbia.edu/mailman/listinfo/music-dsp
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