Maybe we don't need an internal buffer for the ALSA backend?

[JasonLG1979]

I was playing with maybe implementing a proper ring buffer as the internal buffer in the alsa backend (maybe https://docs.rs/rtrb/0.1.4/rtrb as @roderickvd suggested a while ago) and as a sanity check I removed the old vec internal buffer and just changed swp.set_start_threshold to be the size of the entire buffer and dumped bytes directly to the PCM. And well it seems to work just fine. The original logic behind the internal buffer was to save CPU cycles and prevent underruns. I notice no CPU usage difference even on a PiZero and I think changing swp.set_start_threshold takes care of underruns for us by not starting until the buffer is full (the buffer fills much, much faster than realtime. It does not take 0.5 sec to buffer 0.5 sec of audio) and putting us on the tail end of it if you like as far as filling it. From what I understand of the rest of the internals tracks are already buffered to disk or memory anyway. I don't really think another internal buffer is worth the trouble. I could very well be wrong I look forward to any thoughts.

Here is a branch I created to test out if anyone would like?

[kingosticks]

What do you mean "worth the trouble"? This is the usual way to use alsa but you want to ignore that because this seems to work in the environment you have? If it ain't broke... mess with it until it is? I say leave it alone.

[JasonLG1979]

Cool your jets. This isn't a PR it's a discussion about an experiment. Just something I threw out there as an observation on the way to maybe implementing a ring buffer.

[roderickvd]

Alsa caters to a huge palette of sound cards each with their own idiosyncrasies. I think that the current start threshold is something that's quite common in the wild, for what that's worth.

In the initial implementation at 64081a1 @sniperrifle2004 said:

Writing to the pcm more often than necessary is just a waste of resources and depending on the pcm it can have quite an impact
on performance. The pcm expects full periods anyway.

So I don't know but which PCMs would be sensitive to this?

[roderickvd]

Sure go for it.

Where do you live, Australia? Also are working night shifts or or were you just unable to sleep? 😄 considering you say it’s breakfast but have been lurking here for a few hours now?

[JasonLG1979]

Where do you live, Australia? Also are working night shifts or or were you just unable to sleep? smile considering you say it’s breakfast but have been lurking here for a few hours now?

I live in Ankeny, IA (a suburb of Des Moines the state capital) in the Midwestern US. It is 10:45 AM here now. But Yes i am a nigh owl. I've basically worked the graveyard shift my whole life. Plus a lot of you guys are in Europe so I could not talk to you otherwise.

[JasonLG1979]

I'll put in a PR. You'd be surprised how trivial it actually is.

[roderickvd]

👋 from the Netherlands about 40 minutes north of Amsterdam. Good to have you here.

[JasonLG1979]

from the Netherlands about 40 minutes north of Amsterdam. Good to have you here.

Yep, I know I looked at your profile. It's good to be here, most of the time anyway when i'm not making a fool out of myself,lol!!!