Re: ALSA snd_xferi_t buffer arrangment

[James Courtier-Dutton <James@superbug.co.uk>]

Assaf Hoffman wrote:
> Hi,
> 
> I'm mew to sound and ALSA.
> 
> My project deals with PCM in standard (I2S) mode and IEC958 (SPDIF)
> mode. 
> 
> Can anyone tell me how the ALSA stack expects to "see" the data received
> form the sound device? I mean, what is the format of the data DMA'ed
> from the sound device to DRAM that the ALSA stack expects? 
> 
> Is this raw sound data? SPDIF frame includes non sound data as well.
> Does the sound card HW strip the sound payload from the IEC958 frame to
> deliver the raw sound data to the ALSA buffer? 
> 
> Please shed some light...
> 
> Many thanks. 
> 
>  

ALSA can deal with all the different formats that the sound device might
deliver. The low level sound driver simply tells the upper layers what
formats are available. ALSA then handles those formats and all format
conversion required to reach the user space application.
It depends what your device does as to which format ALSA will see.

James





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