GMINL-3234: Reorganize filters a litle

[android-x86/hardware-intel-libsensors.git] / filtering.c

diff --git a/filtering.c b/filtering.c
index 9217de6..adabb30 100644 (file)
--- a/filtering.c
+++ b/filtering.c
@@ -188,3 +188,75 @@ void record_sample (int s, const struct sensors_event_t* event)
 
        memcpy(&cell->data, event, sizeof(sensors_event_t));
 }
+
+
+void denoise_average ( struct sensor_info_t* si, struct sensors_event_t* data,
+                       int num_fields, int max_samples)
+{
+       /*
+        * Smooth out incoming data using a moving average over a number of
+        * samples. We accumulate one second worth of samples, or max_samples,
+        * depending on which is lower.
+        */
+
+       int i;
+       int f;
+       int sampling_rate = (int) si->sampling_rate;
+       int history_size;
+       int history_full = 0;
+
+       /* Don't denoise anything if we have less than two samples per second */
+       if (sampling_rate < 2)
+               return;
+
+       /* Restrict window size to the min of sampling_rate and max_samples */
+       if (sampling_rate > max_samples)
+               history_size = max_samples;
+       else
+               history_size = sampling_rate;
+
+       /* Reset history if we're operating on an incorrect window size */
+       if (si->history_size != history_size) {
+               si->history_size = history_size;
+               si->history_entries = 0;
+               si->history_index = 0;
+               si->history = (float*) realloc(si->history,
+                               si->history_size * num_fields * sizeof(float));
+               if (si->history) {
+                       si->history_sum = (float*) realloc(si->history_sum,
+                               num_fields * sizeof(float));
+                       if (si->history_sum)
+                               memset(si->history_sum, 0, num_fields * sizeof(float));
+               }
+       }
+
+       if (!si->history || !si->history_sum)
+               return; /* Unlikely, but still... */
+
+       /* Update initialized samples count */
+       if (si->history_entries < si->history_size)
+               si->history_entries++;
+       else
+               history_full = 1;
+
+       /* Record new sample and calculate the moving sum */
+       for (f=0; f < num_fields; f++) {
+               /**
+                * A field is going to be overwritten if
+                * history is full, so decrease the history sum
+                */
+               if (history_full)
+                       si->history_sum[f] -=
+                               si->history[si->history_index * num_fields + f];
+
+               si->history[si->history_index * num_fields + f] = data->data[f];
+               si->history_sum[f] += data->data[f];
+
+               /* For now simply compute a mobile mean for each field */
+               /* and output filtered data */
+               data->data[f] = si->history_sum[f] / si->history_entries;
+       }
+
+       /* Update our rolling index (next evicted cell) */
+       si->history_index = (si->history_index + 1) % si->history_size;
+}