+ snd_pcm_sw_params_t *sw_params;
+ snd_pcm_sw_params_alloca(&sw_params);
+ die_on_error("snd_pcm_sw_params_current()", snd_pcm_sw_params_current(pcm_handle, sw_params));
+ die_on_error("snd_pcm_sw_params_set_start_threshold", snd_pcm_sw_params_set_start_threshold(pcm_handle, sw_params, num_periods * period_size / 2));
+ die_on_error("snd_pcm_sw_params()", snd_pcm_sw_params(pcm_handle, sw_params));
+