Hello,

I have developed a piece of code (as LADSPA plugin) which among other things 
multiplexes one of two input streams into output stream.

Though switching worked, latency was several seconds long instead fraction of a 
second.

Initially I was debugging the whole issue using a USB audio card with standard 
USB (coming with the kernel) audio driver.

Because of the latency I suspected a problem with my code, but after creating a 
special test audio files I've established that the multiplexing happens fast - 
within my LADSPA host buffer length, as expected. And the buffer length was 
1024 samples @44100KHz.

So, I tried the same code with built in soundcard and with a PCI sound card - 
in both cases subjectively multiplexing is fast - fraction of a second - as 
expected. I mean, I hear the stream change in a fraction of a second from the 
moment I see in diagnostic print out change of value of the flag determining 
which of the two streams to route to output.

I have yet another standard USB driver USB sound card, and with it again the 
latency is several seconds long.

So, how do I debug this and how to decrease latency ? I.e. into what files to 
look and what to change ? Is it related to UDEV ?

All the above was tested first with plain ALSA, and then with PulseAudio. In 
the latter case latency is slightly higher - as expected. But my point is that 
the problem does not come from PulseAudio.

The OS is OpenSUSE-13.2 32 bits.

Thanks,
  Sergei.


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