Re: Audio recording (using ossaudio)

[David Hopper <dhop%nwlink.com@localhost>]

> On Mar 13, 2020, at 9:54 AM, nia <nia%netbsd.org@localhost> wrote:
> 
> On Tue, Mar 10, 2020 at 08:49:55PM +0200, Yorick Hardy wrote:
>> Can anyone else record audio correctly via ossaudio?
>> audiorecord seems to work as long as the frequency
>> divides the native frequency (see dmesg excerpt below)
> 
> (I missed this post, but got contacted about it directly off-list. I'm
> probably a good person to contact about this sort of thing).
> 
> The sample rate and number of channels need to exactly match the device
> for ideal output.
> 
> The ffmpeg OSS code looks very primitive. I might be persuaded to write
> a backend that does detection of device characteristics. It's basically
> required for proper audio recording on NetBSD. Note that our OSS emulation
> doesn't match the spec exactly, and is also undocumented, so doing anything
> non-trivial is hard. I don't recommend writing new code that uses it for
> that reason.
> 
> Out of curiosity, does Audacity work for you (when set to single channel
> 16-bit PCM, etc - it defaults to 32-bit floats which won't work).

This would be great for me too as I'm investigating NetBSD as a basis for a real-time audio effects engine, which is a bit of a fool's errand at the moment for the reasons above and others.  But this does suggest (at least) to prefer sunau as a backend for JACK instead of OSS, and confirms why NetBSD OSS is tough to work with currently with most modern audio tools.

Identifying the challenges in low-latency audio for NetBSD (and beginning to address them) would make for a great summer of code project-- or even bounty if it's a realistic goal.

Dave