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

[Tanu Kaskinen]

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.

-- 
Tanu

https://liberapay.com/tanuk
https://www.patreon.com/tanuk