[pulseaudio-discuss] [PATCH v6 00/25] Optimize latency handling in module-loopback

[Tanu Kaskinen]

On Sun, 2016-06-05 at 21:05 +0200, Georg Chini wrote:
> Hi,
> 
> finally I got around to split the loopback patches. The current version has
> a lot of improvements over the last version and hopefully incorporates the
> comments from Tanu's previous review. Main features of the new code are:
> 
> - Reduce latency jitter by a factor 100 from around 30 ms to 300 usec
> - Implement modified P-controller and adaptive re-sampling
> - Underrun protection
> - Latency initialisation to avoid underruns
> - Adjust to specified latency if possible, else use minimum possible latency
> - Allow smooth switching between different sources and sinks
> - 3 new parameters
> 
> The intermediate results are tested to compile but not for functionality.
> 
> More details can be found in the individual commit messages. The theoretical
> background of the controller is covered in the document "rate_estimator.odt"
> which I will send in a separate mail. The document also contains some results
> achieved with the new code.
> 
> Georg Chini (25):
>   loopback: Save time stamps during latency snapshots
>   loopback: Improve latency estimation in snapshots
>   loopback: Improve latency estimation
>   loopback: Change memblockq length
>   loopback: Move timer restart and snapshots to time callback
>   loopback: Restart timer after 1/3 second
>   loopback: Adjust rate based on latency difference
>   loopback: Stop tracking max_request and min_memblockq_length
>   loopback: Refactor latency initialization
>   loopback: Do not skip audio at startup
>   loopback: Calculate and track minimum possible latency
>   loopback: Implement underrun protection
>   sample.c: Allow module-loopback to exceed PA_RATE_MAX
>   source.c, sink.c: Implement
>     pa_{source,sink}_get_raw_latency_within_thread() calls
>   alsa-{source,sink}.c: Handle PA_{SOURCE,SINK}_MESSAGE_GET_RAW_LATENCY
>   loopback: Reset sink input rate when source or sink changes
>   loopback: Track and use average adjust time
>   loopback: Limit controller step size to 2.01‰
>   loopback: Implement adaptive re-sampling
>   loopback: Add latency prediction and Kalman filter
>   loopback: Track prediction error; debug and cosmetic changes
>   loopback: Allow shorter adjust_time
>   loopback: Add low_device_latency parameter
>   loopback: Add adjust_threshold_usec parameter
>   loopback: Add log_interval parameter
> 
>  src/modules/alsa/alsa-sink.c   |  25 +-
>  src/modules/alsa/alsa-source.c |  20 +-
>  src/modules/module-loopback.c  | 786 +++++++++++++++++++++++++++++++++--------
>  src/pulse/sample.c             |   5 +-
>  src/pulsecore/sink.c           |  30 ++
>  src/pulsecore/sink.h           |   2 +
>  src/pulsecore/source.c         |  30 ++
>  src/pulsecore/source.h         |   2 +
>  8 files changed, 732 insertions(+), 168 deletions(-)

I pushed the first 8 patches now, since they're fine and I don't need
them to be resubmitted. (I complained about a variable name in patch 2,
but the variable can be renamed in a separate commit.) The 9th patch
had some issues, so patches from that onwards probably need to be
resubmitted. You can resubmit at any time you like, or you can wait
until I've commented on the rest of the patches.

-- 
Tanu