[pulseaudio-discuss] [PATCH v2] pipe-source: suspend source when no writers connected to fifo

[Raman Shishniou]

On 02/13/2018 11:58 AM, Georg Chini wrote:
> On 12.02.2018 17:23, Tanu Kaskinen wrote:
>> On Sat, 2018-02-10 at 23:08 +0100, Georg Chini wrote:
>>> On 10.02.2018 23:04, Raman Shishniou wrote:
>>>> On 02/11/2018 12:43 AM, Georg Chini wrote:
>>>>> On 10.02.2018 22:25, Raman Shuishniou wrote:
>>>>>> 10.02.2018 23:59, Georg Chini пишет:
>>>>>>> On 08.02.2018 17:58, Raman Shyshniou wrote:
>>>>>>>>        Make pipe-source suspended if all writers closed fifo.
>>>>>>>>        Source will be automatically unsuspended if any data will
>>>>>>>>        be written to pipe and suspended again when last writer
>>>>>>>>        closed fifo.
>>>>>>>> ---
>>>>>>>>     src/modules/module-pipe-source.c | 114 +++++++++++++++++++++++++++++++++++++--
>>>>>>>>     1 file changed, 109 insertions(+), 5 deletions(-)
>>>>>>>>
>>>>>>> What is the motivation/use case for the patch? Normally, if there
>>>>>>> are no writers, the source should deliver silence like any other
>>>>>>> source without input signal.
>>>>>> pipe-source module can't generate silence if no writers connected
>>>>>> because it has no clock. Aactually incoming data has some clock, but
>>>>>> not pipe-source itself. Use the system clock to generate silence
>>>>>> is a bad idea because it may differ from incoming data clock.
>>>>> Take a look at the recent patches for pipe-sink that introduced using
>>>>> system-clock timing. I guess something similar should be possible
>>>>> for the pipe-source. Why would it be a problem, if the timing of the
>>>>> silence is slightly different from that of the writer? Different writers
>>>>> may have different timing anyway, so if one writer disconnects
>>>>> and another connects, timing may change.
>>>>> module-loopback is able to deal with sample rate changes on the
>>>>> input side and will adapt the sample rate of the output side so that
>>>>> it matches the incoming rate to keep a constant latency.
>>>>>
>>>> I seen the last patches for pipe-sink module. I think there is no
>>>> reason to generate silence in pipe-source module with system clock.
>>>> The source outputs will do read zeros (resample, convert) - just a
>>>> waste of cpu time.
>>>>    
>>> I see your point. The reason for generating silence would
>>> be to have consistent behavior for all sources. I'll ask Tanu
>>> for his opinion.
>> My opinion: it would be nice to generate silence by default if someone
>> is willing to implement that, but suspending is better than the current
>> behaviour, if the current behaviour is to have the source state as
>> RUNNING while not producing any data.
>>
> Raman, are you willing to implement generating silence? This
> could also cover the case where a writer stays connected but
> does not provide any data.
> 
> If not, I will proceed reviewing your patch.
> 

Ok. I'll implement silence generator, but I want to leave an autosuspend option.

-- 
Raman