[pulseaudio-discuss] Monitoring and Pulseaudio accuracy

Neil Wilson neil at aldur.co.uk
Mon Nov 30 11:51:35 PST 2009

2009/11/30 Tanu Kaskinen <tanuk at iki.fi>:

> Are you sure your files had the same sample format as what your sound
> card uses? If pulseaudio doesn't need to do mixing or resampling or
> sample format conversion, I'm surprised if the bytes are touched.

No they definitely aren't. That's part of the question I suppose. When
does the format get changed? What's the best format to start off in if
you're going out via SPDIF to digital speakers. Is it best to start
off in the sample spec of your sink, or do you have to take the mixer
into account?

And what is the source of the Monitor's output tap. Is it before it
gets to the sink native driver, or does it actually go to the sound
card hardware before coming back?

Certainly it looks like the float32le was converted to s16le before
being converted back in the Monitor output. However nothing in the
pulseaudio log suggested what the conversion would be or when.

> So, you had float32le tones. Is your sink also configured with that
> format (see "pacmd list-sinks")? Do the sample rates match between the
> files and the sink?

The sample rates match, so there is no resampling, and the channel
maps were adjusted so there was no mono to stereo conversion going on.

Neil Wilson

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