On Fri, Feb 21, 2014 at 9:38 AM, Stefano D'Angelo <zanga.mail@gmail.com> wrote:

Sorry guys, other two (silly?) questions:

1. apart from the process callback, which callbacks need to be
RT-safe? Looking around I found a master thesis [1] that says: "Apart
from
the JackProcessCallback callback, which is called in the realtime
audio thread for obvious reasons, all other callbacks are called
asynchronously in a specialized non-realtime thread, to avoid
notifications to interfere with audio processing", is that true?

The documentation does actually state which ones need to be RT, but there is no list to easily consult.

The threading design described above is specific to Jack2. Jack1 delivers all callbacks to the same thread (which necessarily means that processing audio is blocked by other callbacks). This is one of the major (and largely hidden) design differences between Jack1 and Jack2.

2. may the system sample rate actually change (while a client is running)?

JACK to date has never supported changing the sample rate.