[pulseaudio-discuss] [PATCH v4] Make module loopback honor requested latency

[Georg Chini]

On 08.02.2015 20:30, Georg Chini wrote:
> On 08.02.2015 19:54, Alexander E. Patrakov wrote:
>> 01.02.2015 03:43, Georg Chini wrote:
>>> +    /* Minimum number of adjust times + 1 needed to adjust at 0.75% 
>>> deviation from base rate */
>>> +    min_cycles = (double)abs(latency_difference) / u->adjust_time / 
>>> 0.0075 + 1;
>>> +
>>> +    /* Rate calculation, maximum deviation from base rate will be 
>>> less than 0.75% due to min_cycles */
>>> +    new_rate = base_rate * (1.0 + latency_difference / min_cycles / 
>>> u->adjust_time) + 0.5;
>>
>> What's the aim here with min_cycles? Why not just clamp new_rate 
>> post-factum to 0.75% vicinity of base_rate, as this is done in the 2‰ 
>> case?
>>
> Without min_cycles you will far more often hit the 2 ‰ limit and when 
> you are approaching the
> base_rate. This seriously disturbs the regulation. The goal was to get 
> out to 0.75% as quick as
> possible while approaching the base rate cautiously (with a weak 
> regulator when latency is far off).
> Also without min_cycles you see the rates hopping up and down (due to 
> the 2‰ limitation), you do
> not see a (more or less) continuous rate function.

Doing what you suggest would give you 0.75% as long as the latency is 
more than one
cycle off - but from 0.75% rate deviation you need at least 4 steps to 
go back to the
base_rate with the 2 ‰ restriction, so you would seriously over-regulate.


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