[pulseaudio-discuss] [PATCH] sink, source: Add a mode to avoid resampling if possible
Arun Raghavan
arun at arunraghavan.net
Mon Jan 30 08:36:24 UTC 2017
On Mon, 30 Jan 2017, at 01:14 PM, Tanu Kaskinen wrote:
> On Sun, 2017-01-29 at 23:23 +0530, Arun Raghavan wrote:
> >
> > On Sun, 29 Jan 2017, at 02:29 PM, Tanu Kaskinen wrote:
> > > On Sun, 2017-01-29 at 10:29 +0530, Arun Raghavan wrote:
> > > > This adds an "avoid-resampling" option to daemon.conf that makes the
> > > > daemon try to use the stream sample rate if possible (the device needs
> > > > to support it, which currently only ALSA does), and there should not be
> > > > any other stream connected).
> > > >
> > > > This should enable some of the "audiophile" use-cases where users wish
> > > > to play high sample rate audio files without resampling.
> > > >
> > > > We still will do conversion if sample formats don't match, though. This
> > > > means that if you want to play 96 kHz/24 bit audio without any
> > > > modification the default format will need to be set to be 24-bit as
> > > > well. This will force all streams to be upconverted, which, other than
> > > > the wasted resources, should be relatively harmless.
> > > > ---
> > > > man/pulse-daemon.conf.5.xml.in | 9 +++++++++
> > > > src/daemon/daemon-conf.c | 3 +++
> > > > src/daemon/daemon-conf.h | 1 +
> > > > src/daemon/daemon.conf.in | 1 +
> > > > src/daemon/main.c | 1 +
> > > > src/pulsecore/core.h | 1 +
> > > > src/pulsecore/sink.c | 10 ++++++++--
> > > > src/pulsecore/source.c | 9 +++++++--
> > > > 8 files changed, 31 insertions(+), 4 deletions(-)
> > > >
> > > > diff --git a/man/pulse-daemon.conf.5.xml.in b/man/pulse-daemon.conf.5.xml.in
> > > > index b81a549..cb09b97 100644
> > > > --- a/man/pulse-daemon.conf.5.xml.in
> > > > +++ b/man/pulse-daemon.conf.5.xml.in
> > > > @@ -124,6 +124,15 @@ License along with PulseAudio; if not, see <http://www.gnu.org/licenses/>.
> > > > </option>
> > > >
> > > > <option>
> > > > + <p><opt>avoid-resampling=</opt> If set, try to configure the
> > > > + device to avoid resampling. This only works if on devices that
> > >
> > > The extra "if" is still here.
> > >
> > > > @@ -1442,7 +1443,12 @@ int pa_sink_update_rate(pa_sink *s, uint32_t rate, bool passthrough) {
> > > > if (PA_UNLIKELY(!pa_sample_rate_valid(desired_rate)))
> > > > return -1;
> > > >
> > > > - if (!passthrough && default_rate != desired_rate && alternate_rate != desired_rate) {
> > > > + if (avoid_resampling && (rate >= default_rate || rate >= alternate_rate)) {
> > > > + /* We just try to set the sink input's sample rate if it's not too low */
> > > > + if (rate > default_rate || rate > alternate_rate)
> > > > + desired_rate = rate;
> > >
> > > Now the code works, which is nice. However, you said that the
> >
> > I don't know what you're talking about. It was working before, this
> > makes the condition cause the alternate resample rate calculation to be
> > used in the case of avoid_resampling=true and the desired rate being too
> > low. .
>
> I meant that your original patch didn't do what you intended it to do.
> I believe your intention was to not allow the sink rate to be changed
> to a value smaller than default_rate or alternate_rate, but the
> original patch did allow that.
Ah, okay.
> > > "desired_rate = rate" assignment makes the code clearer, but I
> > > disagree. The code looks like the intention is to do something if the
> > > "rate > default_rate || rate > alternate_rate" condition is true, but
> > > actually the code never does anything, regardless of whether the
> > > condition is true or false.
> >
> > That part was wrong, the second if was a duplicate (I fixed it in
> > source.c but not sink.c).
>
> Ok, I didn't notice that source.c was different. (BTW, the indentation
> in source.c is off.)
Fixed.
> > > If you think leaving the code block empty or merging the "if" and "else
> > > if" branches makes the code unclear, then I think a comment is more
> > > appropriate way to clarify things than adding code that doesn't do
> > > anything.
> >
> > I'm not sure I understand -- are you saying the code in source.c is
> > fine, or that it needs to not do anything in the avoid_resampling case
> > (whereas now we have a duplicated "desired_rate = rate")?
>
> The code in source.c is definitely less confusing than the code in
> sink.c. I'd prefer not to have the redundant assignment, but I don't
> mind if you leave it there.
We spoke about this on IRC, and I'm pushing a second patch to make all
the conditions more explicit in this path (and thus remove the early
initialisation).
Cheers,
Arun
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