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

[Alexander E. Patrakov]

09.02.2015 00:35, Georg Chini пишет:
> 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.

Thanks for your answers. Now I consider the adjust_rate() function fully 
reviewed.

So, now (or, rather, tomorrow) I have to properly split this patch, 
taking your explanations into account.

-- 
Alexander E. Patrakov