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

Georg Chini georg at chini.tk
Tue Feb 13 15:41:05 UTC 2018

On 13.02.2018 11:27, Raman Shishniou wrote:
> 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.
Fine for me to keep the autosuspend option. I guess the "silence generator"
will then be another patch on top of this patch?

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