SNDRV_PCM_FMTBIT_S24_LE vs. SNDRV_PCM_FMTBIT_S24_3LE

SNDRV_PCM_FMTBIT_S24_LE vs. SNDRV_PCM_FMTBIT_S24_3LE

[Timur Tabi]

What is the difference between SNDRV_PCM_FMTBIT_S24_LE and SNDRV_PCM_FMTBIT_S24_3LE?

-- 
Timur Tabi
Linux Kernel Developer @ Freescale

Re: SNDRV_PCM_FMTBIT_S24_LE vs. SNDRV_PCM_FMTBIT_S24_3LE

[James Courtier-Dutton]

Timur Tabi wrote:
> What is the difference between SNDRV_PCM_FMTBIT_S24_LE and SNDRV_PCM_FMTBIT_S24_3LE?
> 

SNDRV_PCM_FMTBIT_S24_LE is 24bit audio padded to fill 4 bytes.
SNDRV_PCM_FMTBIT_S24_3LE is 24bit audio with no padding, thus taking 
only 3 types.

Re: SNDRV_PCM_FMTBIT_S24_LE vs. SNDRV_PCM_FMTBIT_S24_3LE

[dustin]

>  ------------ Původní zpráva ------------
>
>  ----------------------------------------
>  What is the difference between SNDRV_PCM_FMTBIT_S24_LE and
>  SNDRV_PCM_FMTBIT_S24_3LE?

The asound.h says S24_LE is stored in lower three bytes of four, whereas S24_3LE is stored in three bytes total.


Pavel.

>  
>  -- 
>  Timur Tabi
>  Linux Kernel Developer @ Freescale
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>  
>  
>  

Re: SNDRV_PCM_FMTBIT_S24_LE vs. SNDRV_PCM_FMTBIT_S24_3LE

[Clemens Ladisch]

dustin@seznam.cz wrote:
> >  What is the difference between SNDRV_PCM_FMTBIT_S24_LE and
> >  SNDRV_PCM_FMTBIT_S24_3LE?
> 
> The asound.h says S24_LE is stored in lower three bytes of four, whereas
> S24_3LE is stored in three bytes total.

To use a sample format with 24 bits stored in the upper three bytes of
four, use S32_LE.  In that case, you have to call
"snd_pcm_hw_constraint_msbits(runtime, 0, 32, 24)" in the PCM open
callback to tell ALSA that some of the lower bits aren't used.


HTH
Clemens