Question

This one is for all you ALSA guys. I need a sanity check here. I am using the the alsa-lib api to play sounds and the function that I am using to write the data to the driver is

snd_pcm_sframes_t snd_pcm_writei (snd_pcm_t* pcm,
                                  const void* buffer,
                                  snd_pcm_uframes_t size);

For the third parameter, should it be the frame count or the size of the buffer in bytes? I’m asking because I have seen numerous examples where the size in bytes is passed in. One example is included in the documentation.

Answer 1

According to the documentation, it’s the amount of frames, not bytes.

In the example you linked to the values just happen to be the same because it’s using 8-bit samples and one channel, and one frame of one channel 8-bit data is one byte.