Re: Audio recording (using ossaudio)

[Tetsuya Isaki <isaki%pastel-flower.jp@localhost>]

At Fri, 20 Mar 2020 08:08:37 +0200,
Yorick Hardy wrote:
> It seems to be stuck in select (or poll, I did not check the source)
> in portaudio.

Yeah, I'm just looking this in this week.
poll()/select() before read() doesn't work correctly now.
I will fix it.

> Updating audio/portaudio from portaudio-190600.20161030nb1 to portaudio-190600.20161030nb2
> fixes the problem (maybe because of the patch to disable non-blocking I/O ?).

I looked it right now.  And it looks bad strategy.
He should have reported it first...

> Now 44100 MHz does not sound right (I will send the example off-list), but
> 48000 MHz is fine (this is the same behaviour as audiorecord).

I heard it but unfortunately I don't know expected status.
It sounded like analog noise or environmental noise.


Anyway, if you want to record with pure 44100Hz, you need to
set the hardware 44100Hz mode using audiocfg(1) command:
 # audiocfg set <index> r slinear_le 16 2 44100

On NetBSD7 (or prior), if you record 44100Hz, the kernel set
the hardware 44100Hz, because it was single audio system.

On NetBSD9 (or later), multiple recorder apps can be run
simultaneously.  So even if your single app want to record
44100Hz, the kernel can not change the hardware frequency.
The kernel converts from the hardware frequency to your
requested frequency (if different).
In-kernel frequency conversion is simple (and fast and small)
than what userland rich apps does (and I personally think that
such rich operation should be done by userland).

You need to a)change the hardware format (by audiocfg) or
b)record as the hardware format ("audiocfg list" displays)
and convert it by userland rich converter.

Thanks,
---
Tetsuya Isaki <isaki%pastel-flower.jp@localhost / isaki%NetBSD.org@localhost>