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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