[PD-dev] Why not use portaudio per default?

[IOhannes m zmoelnig]

i'll start answering before reading your entire message, so...

On 1/21/22 02:58, Christof Ressi wrote:
> Hi,
> 
> here's a question that has been bugging me for quite a while: Why do we 
> keep all those individual audio backends instead of just using portaudio 
> everywhere? Are there any other reasons *besides* backwards 
> compatibility with existing setups (saved preferences)?
> 
> Currently we have the following backend (excluding the dummy backends):
> 
> ALSA: s_audio_alsa.c
> 
> ESD: s_audio_esd.c

minor side-note: ESD is just a dummy.
the Enlightened Sound Daemon died some decade ago.
i'm not sure the Pd backend was ever used.

it should be removed.


> 
> Jack: s_audio_jack.c
> 
> MMIO: s_audio_mmio.c
> 
> OSS: s_audio_oss.c
> 
> portaudio: s_audio_pa.c
> 
> ---
> 
> Portaudio already supports all relevant audio backends 

i never use portaudio, as it never really *worked* for me.
and JACK always worked for me.
i see little merit in abandoning a working system in favour of fixing a 
non-working system.

more importantly: i'm using JACK as the main audio provider for my system.
so the relevant part for me is how portaudio deals with JACK.

and here the trouble starts.
to name but the first that come to my mind:

- in the JACK-graph, Pd now shows up as "PortAudio".
audacity shows up as "PortAudio-71".
unless of course i start audacity first, in which case audacity gets the 
name "PortAudio" and Pd gets the name "PortAudio-67".
(the numeric ID's are obviously generated (probably by JACK itself) to 
make the names unique). thank you very much.
- when using JACK via PortAudio, i can pick a destination where i want 
to send audio to (and vice versa: a source to get audio from).
that is: i can select my USB soundcard, or audacity (or whatever 
application uses the "PortAudio" name...), or... all from within Pd.
while this sounds cool at first glance, it really isn't.
it means that *all* my channels go to a single peer.
but how do i do any non-trivial routing: e.g. [adc~ 1 2] go to my 
soundcard channels 17 & 18 (the headphones), while [adc~ 3 4] go to 
JackTrip and all four channels go to Ardour?
i understand that PortAudio doesn't natively support setting up such 
routing, we have specialized software for that (qJackCtl, patchage,...).
but PortAudio is actually counterproductive, as it insists on connecting 
to a peer - i cannot just pick "JACK - no automatic connection".

- oh, and while I *must* pick a peer, only peers that where available 
when i started Pd show up.

- finally, when i start Pd with PortAudio, i get a lot of output on the 
cmdline:
~~~
ALSA lib pcm.c:2664:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.rear
ALSA lib pcm.c:2664:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.center_lfe
ALSA lib pcm.c:2664:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.side
ALSA lib pcm_route.c:877:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:877:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:877:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:877:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_a52.c:1001:(_snd_pcm_a52_open) a52 is only for playback
ALSA lib confmisc.c:160:(snd_config_get_card) Invalid field card
ALSA lib pcm_usb_stream.c:482:(_snd_pcm_usb_stream_open) Invalid card 'card'
ALSA lib confmisc.c:160:(snd_config_get_card) Invalid field card
ALSA lib pcm_usb_stream.c:482:(_snd_pcm_usb_stream_open) Invalid card 'card'
~~~

it seems that whatever these printouts mean to tell me is rather 
harmless, but even so it is a lot of noise that i would rather not see.

- finally when Pd *initializes* PortAudio i get one or more very nasty 
and loud click sounds (about 0dBFS). presumably this is because of some 
samplerate switching (but i really don't know).


so the question is: can we fix these problems within Pd?
afaict the answer is "no".
my reference PortAudio application is audacity, which shows exactly 
*all* of the problems described above.


for me this is really enough to not pick PortAudio.
(esp. since the existing JACK backend does not have any of these problems).
i guess most people do not hear the click sound when initializing 
PortAudio (it makes it unusable in any live performance context; and 
there are *some* applications that only offer PortAudio as a backend 
that i would think have widespread use).
and probably many people do not care about the routing issues, because 
they only ever do trivial routing.

but for me, it's a no-go.

gmadrs
IOhannes
-------------- next part --------------
A non-text attachment was scrubbed...
Name: OpenPGP_signature
Type: application/pgp-signature
Size: 840 bytes
Desc: OpenPGP digital signature
URL: <http://lists.puredata.info/pipermail/pd-dev/attachments/20220121/7d852fc4/attachment.sig>