01.02.2015 03:43, Georg Chini wrote:
This is the final version of my patch for module-loopback. It is on top of the
patch I sent about an hour ago and contains a lot more changes than the previous
versions:
- Honor specified latency if possible, if not adjust to the lowest possible
value
- Smooth switching from fixed latency to dynamic latency source or sink and
vice versa
- good rate and latency stability, no rate oscillation
- adjusts latency as good as your setup allows
- fast regulation of latency offsets, adjusts 100 ms offset within 22 seconds
(adjust
time=1) to 60 seconds (adjust_time=10)
- usable latency range 4 - 30000 ms
- Avoid rewinds and "cannot peek into queue" messages during startup and
switching
- works with rates between 200 and 190000 Hz
- maximum latency offset after source/sink switch or at startup around is 200 ms
I also introduced a new parameter, buffer_latency_msec which can be used
together
with latency_msec. If buffer_latency_msec is specified, the resulting latency
will be latency_msec + buffer_latency_msec. Latency_msec then refers only to
the source/sink latency while buffer_latency_msec specifies the buffer part.
This can be used to save a lot of CPU at low latencies, running 10 ms latency
with latency_msec=6 buffer_latency_msec=4 gives 8% CPU on my system compared to
12% when I only specify latency_msec=10.
Is there any more detailed profiling data for it? E.g., have you tried
running perf record / perf report?
I am not quoting the patch, but my opinion is that it needs either
comments or some text in the commit message on the following topics:
Why does it use hand-crafted heuristics instead of a PID-controller? Or,
is this "Low pass filtered difference between expectation value and
observed latency" a PI controller in disguise?
How was the lowpass filter tuned?
--
Alexander E. Patrakov
_______________________________________________
pulseaudio-discuss mailing list
pulseaudio-discuss@lists.freedesktop.org
http://lists.freedesktop.org/mailman/listinfo/pulseaudio-discuss
