On 16.04.19 19:19, Tanu Kaskinen wrote:
On Thu, 2019-04-11 at 20:42 +0200, Georg Chini wrote:
On 11.04.19 19:36, Tanu Kaskinen wrote:
On Thu, 2019-04-11 at 15:16 +0200, Georg Chini wrote:
On 08.04.19 09:27, Georg Chini wrote:
On 05.04.19 13:29, Tanu Kaskinen wrote:
On Tue, 2019-04-02 at 20:28 +0200, Georg Chini wrote:
On 06.11.18 22:14, Andrea A wrote:
Hi Andrea,
maybe there is a chance now to have your equalizer included as a
module.
The messaging API patches
should have their final form (at least I do not think the public
functions will change anymore) and today
I submitted a patch series that consolidates the code of the current
virtual sinks and moves the common
code to a separate file. Using the common code should significantly
reduce the maintenance cost of an
additional sink.
So if you are still interested to have it included, at least I would
welcome a new patch.
Arun, Tanu, what do you think?
I think it would anyway make sense to make one or more LADSPA plugins
out of the equalizer code (I say one or more, because of the lack of
parametrization support in LADSPA). That way the equalizer would be
available also to other software than just PulseAudio (I'm thinking
PipeWire in particular).
If a suitable LADSPA plugin existed, we might or might not still need a
separate equalizer module, but in any case we wouldn't need to maintain
the DSP code in PulseAudio. If there's some reason why module-ladspa-
sink isn't (and can't become) suitable for implementing the integration
in PulseAudio, then a specialized module is fine.
I'm not saying that I'm dead against hosting the DSP code in
PulseAudio, but I'd certainly prefer not to.
It surely would make sense to have one or several LADSPA
plugins, but for me a good equalizer should be an integral
part of pulseaudio. And as you say yourself, the full flexibility
cannot be achieved by a single LADSPA plugin. The equalizer
we are currently providing is buggy and completely unsupported.
The new equalizer would at least be fully documented, so that
it is possible to maintain. Additionally I agree with Andrea that
handling LADSPA plugins is somewhat cumbersome. From a
user point of view, a module is much easier to handle.
I have taken a more detailed look on the LADSPA standard and
to me it appears like you would not only need different plugins for
different numbers of equalizer channels but in addition also
for different number of audio channels. Both, the number of
single-value parameters and number of input-/output-channels
seem to be fixed, so producing a bunch of plugins is rather
impractical.
An equalizer plugin doesn't need multiple channels, one mono plugin can
be instantiated for each channel. Or does this equalizer have some
cross-channel effects?
You are right, that would not be necessary. Only some plugin
that does up- or down-mixing of channels would need that.
I wonder if there is a chance to extend the standard a bit to
allow a variable number of audio channels and allow control
ports to be arrays. It can be done with two more constants and
one additional function, see attached diff. This extension would
allow to reduce many of our virtual sinks to one plugin-sink and
also allow full integration of Andrea's equalizer.
Do you have in mind actually extending the LADSPA standard (i.e.
something to be promoted to other projects as well), or just creating a
new custom (i.e. non-standard) plugin API for PulseAudio that is based
on LADSPA?
It would be actually best if the standard could be extended, but
I do not know how feasible this is. The extension I provided will
not break any old plugin and would simplify the handling in many
cases.
The next best thing would be to do it only for PA.
I doubt the wider Linux audio community is very interested in extending
LADSPA, since LV2 already exists as a successor.
Defining a PA specific filter API would be worth doing, IMO, if it can
be kept simple (compared to the alternatives). Of course anyone would
be welcome to use it in other projects too (the API should be stable,
so there should be no problems with maintaining plugin compatibility).
If you want a better plugin standard, are you aware of LV2
and PipeWire's SPA (the latter doesn't seem to be properly documented
yet, but to my understanding it's supposed to have a stable and
flexible API)?
Arun already suggested the pipewire SPA. I took a look, but it
seems not very simple compared to LADSPA. I could not really
understand how it works and it appears to support a lot more
than just filters.
LV2 would also be an option, although it too is pretty complex compared
to LADSPA. But at least it's documented and has examples.
I just took a look and on the first glance LV2 seems similar
to LADSPA. I have to dig into the details though, maybe control
arrays and interleaved audio ports are possible there.
You say that your extension allows full integration of Andrea's
equalizer, but I don't see how it allows the host to tell the plugin
how many channels and how many frequency bands it should initialize.
For an interleaved audio port, there would be another control
port which holds the number of (interleaved) channels. So
this port would allow you to change the number of channels.
You could for example have an audio port named "Input"
and a control port "Number of input channels". Then the
get_info_port() function would return the index of the
"Number of input channels" control when called with the
"Input" port as argument. Or the other way round: If you
set "Number of input channels" to 6 the plugin will expect
6 channels in the interleaved audio port (and you know
which control port sets the number of channels because
you can get it via the get_info_port() function.
The same applies to the number of bands. There must be a
control port which reflects the number of elements in the
control array which is the same as the number of bands.
Both values can be set to convenient defaults if the host does
not supply them (like 5 bands and 2 channels).
Ok, so the idea is to do the configuration while the filter is running.
I think it would be better to do the configuration in the plugin setup
phase. I imagine that would simplify the control port allocoation and
management, since the setup doesn't have to run in the IO thread where
malloc() is not allowed. I don't see much benefit in doing this kind of
configuration while the filter is running, since the filter state most
likely has to be reset anyway when the number of EQ bands is changed.
There could be a function for getting a description of what options the
plugin accepts, and a setup function for setting the options.
Why do you think that the filter must be configured while it is
running? In case of the equalizer the number of channels and
also the number of bands are known before the filter is run.
The LADSPA standard says all control ports must be connected
(and valid) before you can run the filter. If a parameter changes
at runtime, the filter must be reset like the current ladspa-sink
does.
_______________________________________________
pulseaudio-discuss mailing list
pulseaudio-discuss@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/pulseaudio-discuss
