Query about SNDRV_PCM_FORMAT_S24_LE

Query about SNDRV_PCM_FORMAT_S24_LE

[Patrick Lai]

Hi,

The DSP I am working with currently supports 24-bit PCM sample in
32-bit data space but with LSB padded. Based on the discussion I found
on line, SNDRV_PCM_FORMAT_S24_LE is defined to be 24-bit PCM sample in
32-bit data space with MSB padded. Also, there is no format macro
defined for the format which my DSP supports. Please correct me if I am
wrong. Furthermore, which software layer in audio stack of a typical
linux distribution such as ubuntu handles the padding. I don't think
it's handled by the alsa library. Does application or pulseaudio handle
the padding? I would think it's done in pulseaudio. I have not study
pulseaudio codec extensively but would think someone on the mailing
list can give a quick answer.

Thanks
Patrick
-- 
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.

Re: Query about SNDRV_PCM_FORMAT_S24_LE

[Takashi Iwai]

At Thu, 28 Feb 2013 00:08:46 -0800,
Patrick Lai wrote:
> 
> Hi,
> 
> The DSP I am working with currently supports 24-bit PCM sample in
> 32-bit data space but with LSB padded. Based on the discussion I found
> on line, SNDRV_PCM_FORMAT_S24_LE is defined to be 24-bit PCM sample in
> 32-bit data space with MSB padded. Also, there is no format macro
> defined for the format which my DSP supports. Please correct me if I am
> wrong. Furthermore, which software layer in audio stack of a typical
> linux distribution such as ubuntu handles the padding. I don't think
> it's handled by the alsa library. Does application or pulseaudio handle
> the padding? I would think it's done in pulseaudio. I have not study
> pulseaudio codec extensively but would think someone on the mailing
> list can give a quick answer.

In that case, the format itself is identical with S32_LE.
You can inform the msbits width via snd_pcm_hw_constraint_msbits() if
needed.


Takashi