bpa wrote: 
> my basic understanding.
> 
> PCM Audio is sent via ALSA interface to ALSA device driver.
> 
> Audio samples are put into a ring buffer. 
> The ring buffer size is controlled by the buffer parameter.  
> The ring buffer is processed in terms of periods (i.e there x periods in
> the whole buffer). 
> A period the number of frames per h/w interrupts (edit: corrected from
> first post)
> I don't know how samples are fitted into frames.
> 
> The audio samples can either be copied into buffer using API Read/write
> or the buffer can be memory mapped into calling process memory so no
> additional copying of audio data.
> 
> These are all hardware paramaters and so valid values are dependent on
> the audio device.
> 
> edit:
> 
> Found an explanation of frames and periods.
> 
> 
> https://www.alsa-project.org/main/index.php/FramesPeriods
> 
> edit 2:
> 
> Working link to writing-an-alsa-driver.pdf
> https://www.ibr.cs.tu-bs.de/theses/kurtisi/NMP-EmbeddedClient/Abgabe/Quellen/writing-an-alsa-driver.pdf

That's great and it makes a lot more sense now. Thanks very much!



SB3 -> Quad 909 -> Quad Electrostatic speakers, Quad 405 -> TBI
subwoofer
3 x SB3s + SB Radio
LMS on Raspbian on a Pi4
Rotel RSP1068 surround processor, Quad 707 -> B&W surround
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