Re: [Jack-Devel] Mixing midi streams

On Thu, Mar 22, 2012 at 2:12 PM, Dénes Almási <[hidden]> wrote:
> Hi!
>
> I would like to ask, what is the convenient way for mixing two midi streams?
> Or more generally, what is the way mixing two streams where trivial methods
> like adding the two signals don't work? (I will have to do this not only
> with
> midi but some other custom protocols.)
>
> My best guess would be having the streams in a fixed order and for each
> period
> the first stream would be simply copied to an output buffer while for any
> additional streams if a current position is already occupied in the output,
> the
> closest empty places 'in the future' would be filled with the new data. But
> this
> seems to be a bit harsh...

you have to do a merge-sort operation on both input sources. in pseudo-code:

src1 = read midi event from first source
src2 = read midi event from second source

while (1) {
      if (!src1 && !src2) {
              break;
      }
	
      if (!src2 || src1->when < src2->when) {
             write src1 to new output buffer
             src1 = read next midi event from first source
             continue;
      }

      if (!src1 || src2-> when <= src1->when) {
            write src2 to new output buffer
            src2 = read next midi event from second source
      }
}

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