Author Topic: Using a tempo stream with tempo of 1.0 and matching channel/mixer frequency  (Read 501 times)


  • Posts: 48

My iOS app streams music or plays from local files and is mostly for music but offer support for audio books too.

One of the features I want for audio books is to increase the tempo so users can listen to books quicker but without sounding like a chipmunk is reading it.  The interface is the same for playing any audio, so the tempo button is available all the time and I'd like it to have an instant affect on the current audio.

To do this, I have implemented a tempo stream as a decode only stream which I add to a mixer. I can now successfully alter the tempo as desired.  For most scenarios of use, the tempo stream will not be used - no one wants to listen to their music at a higher tempo - but it will still be sitting there in-line. 

My question in, with the tempo stream setup with a matching frequency to the channel & mixer and a tempo of 1.0 - will it simply do no processing on the stream and pass it to the mixer?  I don't want the sound quality affected for the majority of users, to offer a feature for the minority.



  • Posts: 20
Good question, I don't have the answer but would like to know this also.

Ian @ un4seen

  • Administrator
  • Posts: 22327
I just checked, and the sample data is still being processed/modified when the tempo is left at 100%, but not by much. In my little test, the difference didn't get above -72dB. I guess it may be that without the data going through the processing there could be a discontinuity/click when the tempo is changed from 100%.