[alsa-devel] How to properly handle variable samplerate?

[Alexander E. Patrakov]

05.09.2014 22:20, Petr Kulhavy wrote:
> Hi,
>
> I'm developing an audio stream player application with ALSA output, the
> player has a large software buffer. The trouble is that the stream can
> potentially change the sampling rate (e.g. streaming RTP from a VLC
> playlist created from different MP3 songs). How to properly handle this?
>
> I'm thinking of the following concept:
> The codec feeds data into the software buffer together with markers for
> sample rate changes. The ALSA playback is asynchronous, using a callback
> function feeding the data from the software buffer into ALSA. If a
> samplerate marker is hit the new rate is set.
>
> Can the sample rate be set from a callback? What other constraints are
> there? And how does the HW FIFO handle samplerate changes?
> Or is there a better way of implementing?

ALSA does not support variable sample rate at all. So you either have to 
do the variable-rate resampling yourself in your player, or depend on 
PulseAudio which does support this feature.

-- 
Alexander E. Patrakov