[pulseaudio-discuss] [PATCH 06/13] loopback: Restart the timer right away

[Tanu Kaskinen]

On Wed, 2015-02-25 at 19:43 +0100, Georg Chini wrote:
> Move the timer restart to the beginning of the callback function.

Please try to remember to always answer the question "why" in commit
messages.

> ---
>  src/modules/module-loopback.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/src/modules/module-loopback.c b/src/modules/module-loopback.c
> index f9255ee..79bd106 100644
> --- a/src/modules/module-loopback.c
> +++ b/src/modules/module-loopback.c
> @@ -196,9 +196,6 @@ static void adjust_rates(struct userdata *u) {
>      pa_assert(u);
>      pa_assert_ctl_context();
>  
> -    pa_asyncmsgq_send(u->sink_input->sink->asyncmsgq, PA_MSGOBJECT(u->sink_input), SINK_INPUT_MESSAGE_LATENCY_SNAPSHOT, NULL, 0, NULL);
> -    pa_asyncmsgq_send(u->source_output->source->asyncmsgq, PA_MSGOBJECT(u->source_output), SOURCE_OUTPUT_MESSAGE_LATENCY_SNAPSHOT, NULL, 0, NULL);
> -
>      /* Rates and latencies*/
>      old_rate = u->sink_input->sample_spec.rate;
>      base_rate = u->source_output->sample_spec.rate;
> @@ -236,8 +233,6 @@ static void adjust_rates(struct userdata *u) {
>      /* Set rate */
>      pa_sink_input_set_rate(u->sink_input, new_rate);
>      pa_log_debug("[%s] Updated sampling rate to %lu Hz.", u->sink_input->sink->name, (unsigned long) new_rate);
> -
> -    pa_core_rttime_restart(u->core, u->time_event, pa_rtclock_now() + u->adjust_time);
>  }
>  
>  /* Called from main context */
> @@ -248,6 +243,13 @@ static void time_callback(pa_mainloop_api *a, pa_time_event *e, const struct tim
>      pa_assert(a);
>      pa_assert(u->time_event == e);
>  
> +    /* Restart timer right away */
> +    pa_core_rttime_restart(u->core, u->time_event, pa_rtclock_now() + u->adjust_time);

If the goal of this change is to make the wakeups happen exactly with
adjust_time intervals instead of adjust_time + time taken in servicing
the timer interrupt, wouldn't it be better to have a counter of the
timer events and use start_time + counter * adjust_time as the time
value here? That way the average interval should become exactly
adjust_time.

> +
> +    /* Get sink and source latency snapshot */
> +    pa_asyncmsgq_send(u->sink_input->sink->asyncmsgq, PA_MSGOBJECT(u->sink_input), SINK_INPUT_MESSAGE_LATENCY_SNAPSHOT, NULL, 0, NULL);
> +    pa_asyncmsgq_send(u->source_output->source->asyncmsgq, PA_MSGOBJECT(u->source_output), SOURCE_OUTPUT_MESSAGE_LATENCY_SNAPSHOT, NULL, 0, NULL);
> +
>      adjust_rates(u);
>  }
>  
> @@ -257,7 +259,7 @@ static void enable_adjust_timer(struct userdata *u, bool enable) {
>          if (u->time_event || u->adjust_time <= 0)
>              return;
>  
> -        u->time_event = pa_core_rttime_new(u->module->core, pa_rtclock_now() + u->adjust_time, time_callback, u);
> +        u->time_event = pa_core_rttime_new(u->module->core, pa_rtclock_now() + 333 * PA_USEC_PER_MSEC, time_callback, u);

What is this about?

-- 
Tanu