link against SSE enabled rubberband / soundtouch

[Daniel Schürmann]

It turns out, that Ubuntus rubberband and soundtouch are compiled for i386 without using the advantage of the fast sse registers.
We should consider to provide a sse enabled version for these libaries, since they are mayor CPU eaters in the audio callback.

soundtouch uses just -O3 in Ubuntu Trusty
rubberband uses just -O2 in Ubuntu Trusty

Adding -msse -mfpmath=sse will do the job.

[Owen Williams (ywwg)]

Note this comment block in rubberband:

"/* evaluation of 4 sines at onces, using only SSE1+MMX intrinsics so
   it runs also on old athlons XPs and the pentium III of your grand
   mother.

   The code is the exact rewriting of the cephes sinf function.
   Precision is excellent as long as x < 8192 (I did not bother to
   take into account the special handling they have for greater values
   -- it does not return garbage for arguments over 8192, though, but
   the extra precision is missing).

   Note that it is such that sinf((float)M_PI) = 8.74e-8, which is the
   surprising but correct result.

   Performance is also surprisingly good, 1.33 times faster than the
   macos vsinf SSE2 function, and 1.5 times faster than the
   __vrs4_sinf of amd's ACML (which is only available in 64 bits). Not
   too bad for an SSE1 function (with no special tuning) !
   However the latter libraries probably have a much better handling of NaN,
   Inf, denormalized and other special arguments..

   On my core 1 duo, the execution of this function takes approximately 95 cycles.

   From what I have observed on the experiments with Intel AMath lib, switching to an
   SSE2 version would improve the perf by only 10%.

   Since it is based on SSE intrinsics, it has to be compiled at -O2 to
   deliver full speed.
*/
"

[Daniel Schürmann (daschuer)]

For me it looks like Ubuntu's rubberband version has no SSE1+MMX register enabled so it uses the slow i386 floating point unit.
Any Idea how we can verify it?

[RJ Skerry-Ryan (rryan)]

This isn't a problem for Windows or Mac.

We don't control our Debian package so we can't actually fix this in Debian. Our Debian maintainer will strip out any bundling we attempt to do with RubberBand or SoundTouch.

Our PPA is the only place we can do something for this on Linux. If somebody wants to give me a shell script that produces a source package for librubberband or libsoundtouch then I can publish this to our PPA.

[Daniel Schürmann (daschuer)]

Our Debian maintainer .. who is it?
We may discuss a solution with him, something like providing an alternative package version.
I think all Rubberband / SoundTouch dependants will benefit from it.

[Swiftb0y (swiftb0y)]

Mixxx now uses GitHub for bug tracking. This bug has been migrated to:
https://github.com/mixxxdj/mixxx/issues/7771