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

Georg Chini georg at chini.tk
Tue Feb 13 08:58:45 UTC 2018

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.

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