Merge "LE: Add is_connected() function (1/3)"
diff --git a/modules/usbaudio/audio_hw.c b/modules/usbaudio/audio_hw.c
index 4b50d58..b88fa53 100644
--- a/modules/usbaudio/audio_hw.c
+++ b/modules/usbaudio/audio_hw.c
@@ -383,6 +383,24 @@
}
/*
+ * Returns the supplied value rounded up to the next even multiple of 16
+ */
+static unsigned int round_to_16_mult(unsigned int size) {
+ return (size + 15) & 0xFFFFFFF0;
+}
+
+/*TODO(pmclean) - Evaluate if this value should/can be retrieved from a device-specific property */
+#define MIN_BUFF_TIME 5 /* milliseconds */
+
+/*
+ * Returns the system defined minimum period size based on the supplied sample rate
+ */
+static unsigned int calc_min_period_size(unsigned int sample_rate) {
+ unsigned int period_size = (sample_rate * MIN_BUFF_TIME) / 1000;
+ return round_to_16_mult(period_size);
+}
+
+/*
* Reads and decodes configuration info from the specified ALSA card/device
*/
static int read_alsa_device_config(int card, int device, int io_type, struct pcm_config * config)
@@ -405,7 +423,14 @@
config->channels = pcm_params_get_min(alsa_hw_params, PCM_PARAM_CHANNELS);
config->rate = pcm_params_get_min(alsa_hw_params, PCM_PARAM_RATE);
- config->period_size = pcm_params_get_max(alsa_hw_params, PCM_PARAM_PERIODS);
+ config->period_size = pcm_params_get_min(alsa_hw_params, PCM_PARAM_BUFFER_SIZE);
+ /* round this up to a multiple of 16 */
+ config->period_size = round_to_16_mult(config->period_size);
+ /* make sure it is above a minimum value to minimize jitter */
+ unsigned int min_period_size = calc_min_period_size(config->rate);
+ if (config->period_size < min_period_size) {
+ config->period_size = min_period_size;
+ }
config->period_count = pcm_params_get_min(alsa_hw_params, PCM_PARAM_PERIODS);
unsigned int bits_per_sample = pcm_params_get_min(alsa_hw_params, PCM_PARAM_SAMPLE_BITS);