Hello,

I am working on an embedded device which does audio playback. Now when the user presses a key, we want to play a tone to provide a keyclick feedback to the user.

What we always did (we were using OSS before) was pretty much the simplest thing possible which is for the application to: -stop sending playback samples -send the keyclick samples -resume sending the playback samples

With our new hardware this approach does not produce good results because of the size of the device's ringbuffer. The larger buffer introduces a significant latency issue for the user feedback. Reducing the ring buffer size is not a viable option to ensure no underruns are generated on the system.

Now I was wondering if there a good approach for this using alsa. Checking the api, a simple solution would be to: -call snd_pcm_drop -send the keyclick samples -resume sending the playback samples

I've tried this and the latency is good, unfortunately there is the drawback that some samples were dropped. So I guess the application could : -keep a copy of the samples sent, -check the amount of samples left in the ringbuffer before calling snd_pcm_drop, -send the keyclick -resend dropped samples -resume sending the playback samples

Seems a little overcomplicated so I was wondering if I was missing something. Would there be a simpler approach? Something like pausing the stream or reading the contents of the ringbuffer before dropping.

Thanks Marc