On Wed, Nov 12, 2014 at 2:30 PM, Alexander E. Patrakov <patrakov at gmail.com> wrote: > 12.11.2014 15:59, Andrey Semashev wrote: >> >> On Wed, Nov 12, 2014 at 12:26 PM, Alexander E. Patrakov >> <patrakov at gmail.com> wrote: >>> >>> >>> We generally don't need a zoo of resamplers. But you have definitely >>> changed >>> something important from an earlier submission by Peter Meerwald so that >>> the >>> CPU figure became much better. I guess, that's SOXR_LINEAR_PHASE - that's >>> the only obvious change. >> >> >> SOXR_LINEAR_PHASE is 0, I added it mostly for documentation purpose, >> in case if someone wants to add more modes with different phase >> response presets. There is also another difference in that I >> explicitly specify interleaved sample formats, although it is >> numerically equivalent to those without the _I suffix. >> >> I think, the essential difference is quality. Peter's patches use >> SOXR_QQ, while mine use other presets. I didn't add QQ because I don't >> see much point in this mode. > > Indeed, QQ is just cubic interpolation, worse than speex-float-0. However, I > have tried to change that to other values in the old patches, and the result > was a good resampler that ate a lot more CPU than speex-float-5. Note, > however, that the test was done with a Haswell (year 2013) earlier and with > an Arrandale (year 2010) now. I also noticed that Peter's patch supplied runtime_spec to soxr_create(), with the number of threads equal to 0 (i.e. auto-detected). In this case the library uses OpenMP to parallelize some operations. In my patch the default is used, which means 1 thread and no OpenMP. On small frames of audio, the overhead of OpenMP can probably outweigh the benefit.
