Some tweaks to the median filter

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

diff --git a/transform.c b/transform.c
index e86fe1a..1993169 100644 (file)
--- a/transform.c
+++ b/transform.c
@@ -12,6 +12,7 @@
 #include "description.h"
 #include "transform.h"
 #include "utils.h"
+#include "filtering.h"
 
 /*----------------------------------------------------------------------------*/
 
@@ -189,21 +190,27 @@ static void reorder_fields(float* data,   unsigned char map[MAX_CHANNELS])
 
 
 static void denoise (struct sensor_info_t* si, struct sensors_event_t* data,
-                    int num_fields)
+                    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;
-       float total;
        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 in case of a very high sampling rate */
-       if (sampling_rate > 100)
-               history_size = 100;
+       /* 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;
 
@@ -214,32 +221,43 @@ static void denoise (struct sensor_info_t* si, struct sensors_event_t* data,
                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)
+       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 */
-       for (f=0; f < num_fields; f++)
-               si->history[si->history_index * num_fields + f] = data->data[f];
-
-       /* Update our rolling index (next evicted cell) */
-       si->history_index = (si->history_index + 1) % si->history_size;
-
-       /* For now simply compute a mobile mean for each field */
+       /* Record new sample and calculate the moving sum */
        for (f=0; f < num_fields; f++) {
-               total = 0;
+               /**
+                * 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];
 
-               for (i=0; i < si->history_entries; i++)
-                               total += si->history[i * num_fields + f];
+               si->history[si->history_index * num_fields + f] = data->data[f];
+               si->history_sum[f] += data->data[f];
 
-               /* Output filtered data */
-               data->data[f] = total / si->history_entries;
+               /* 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;
 }
 
 
@@ -254,21 +272,24 @@ static int finalize_sample_default(int s, struct sensors_event_t* data)
 
        switch (sensor_type) {
                case SENSOR_TYPE_ACCELEROMETER:
+                       /* Always consider the accelerometer accurate */
+                       data->acceleration.status = SENSOR_STATUS_ACCURACY_HIGH;
                        if (sensor_info[s].quirks & QUIRK_NOISY)
-                               denoise(&sensor_info[s], data, 3);
+                               denoise(&sensor_info[s], data, 3, 20);
                        break;
 
                case SENSOR_TYPE_MAGNETIC_FIELD:
                        calibrate_compass (data, &sensor_info[s], get_timestamp());
                        if (sensor_info[s].quirks & QUIRK_NOISY)
-                               denoise(&sensor_info[s], data, 3);
+                               denoise(&sensor_info[s], data, 3, 100);
                        break;
 
                case SENSOR_TYPE_GYROSCOPE:
                case SENSOR_TYPE_GYROSCOPE_UNCALIBRATED:
-                       calibrate_gyro(data, &sensor_info[s]);
+                       if (!(sensor_info[s].quirks & QUIRK_TERSE_DRIVER))
+                               calibrate_gyro(data, &sensor_info[s]);
                        if (sensor_info[s].quirks & QUIRK_NOISY)
-                               denoise(&sensor_info[s], data, 3);
+                               denoise_median(&sensor_info[s], data, 3);
                        break;
 
                case SENSOR_TYPE_LIGHT: