ALSA driver

ranchu

Guru 20755 points

Hello,

I would like to ask if it is possible to resample, i.e. downsample or upsample in rx and tx direction.
What is the system call which does this resampling. I am using RDK linux, ALSA driver with DM8168,

Best Regards,

Ran

over 11 years ago

0 Clemens Ladisch over 11 years ago

Guru 283600 points

Neither the hardware nor the kernel driver are capable of resampling.

If your userspace accesses the device through alsa-lib, you can use its software resampler.

0 ranchu over 11 years ago in reply to Clemens Ladisch

Guru 20755 points

Hi Clemens,

I see that the application uses API which are probably alsa-lib. I understand that I can now downsample or upsample using the library, though I did not yet find the API for that.

Best Regards,

Ran

0 Clemens Ladisch over 11 years ago in reply to ranchu

Guru 283600 points

Resampling is automatically enabled if you use a device name like "default" or "plughw". "hw" would bypass all alsa-lib enhancements.

0 ranchu over 11 years ago in reply to Clemens Ladisch

Guru 20755 points

Hi Clemens,

Thank you very much for the answers.
In my case device nsame is "plughw" so I see that resampling is automatically enabled, but is there an API for changing the input rate or changing the playback sampling rate ?
Can it be change to any value ?

Best Regards,

Ran

0 Clemens Ladisch over 11 years ago in reply to ranchu

Guru 283600 points

The "plughw" device behaves like a device that supports all sample rates.

To change the input rate, just use another rate.

The playback sample rate is the nearest rate actually supported by the hardware.

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