From 80eabf5acb60ee1576e397b54f5086bb27648cc6 Mon Sep 17 00:00:00 2001
From: Ahmet Inan <xdsopl@googlemail.com>
Date: Fri, 2 Jan 2015 13:25:36 +0100
Subject: [PATCH] normalize amplitude from avg absolute amplitude

---
 app/src/main/rs/decoder.rs         | 11 ++++++-----
 app/src/main/rs/initialization.rsh |  2 +-
 app/src/main/rs/state.rsh          |  2 +-
 3 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/app/src/main/rs/decoder.rs b/app/src/main/rs/decoder.rs
index 2c0a3f6..4932735 100644
--- a/app/src/main/rs/decoder.rs
+++ b/app/src/main/rs/decoder.rs
@@ -145,13 +145,14 @@ void decode(int samples) {
     *saved_width = 0;
     *saved_height = 0;
     for (int sample = 0; sample < samples; ++sample, ++buffer_pos) {
-        float amp = audio_buffer[sample] / 32768.0f;
-        float power = amp * amp;
-        if (filter(&avg_power, power) < 0.0000001f)
+        int amp = audio_buffer[sample];
+        float avg_amp = filter(&avg_amplitude, abs(amp));
+        if (avg_amp < 16.0f)
             continue;
+        float norm_amp = amp / avg_amp;
 
-        complex_t cnt_baseband = convert(&cnt_ddc, amp);
-        complex_t dat_baseband = convert(&dat_ddc, amp);
+        complex_t cnt_baseband = convert(&cnt_ddc, norm_amp);
+        complex_t dat_baseband = convert(&dat_ddc, norm_amp);
 
         float cnt_value = demodulate(&cnt_fmd, cnt_baseband);
         float dat_value = demodulate(&dat_fmd, dat_baseband);
diff --git a/app/src/main/rs/initialization.rsh b/app/src/main/rs/initialization.rsh
index 3a3317a..ee08ae6 100644
--- a/app/src/main/rs/initialization.rsh
+++ b/app/src/main/rs/initialization.rsh
@@ -82,7 +82,7 @@ void initialize(float rate, int length, int width, int height)
     const float dat_bandwidth = 800.0f;
     const float cnt_bandwidth = 200.0f;
 
-    avg_power = ema_cutoff(10.0f, sample_rate);
+    avg_amplitude = ema_cutoff(10.0f, sample_rate);
     leader_lowpass = ema_cutoff(100.0f, sample_rate);
 
     cnt_ddc = ddc(cnt_carrier, cnt_bandwidth, sample_rate);
diff --git a/app/src/main/rs/state.rsh b/app/src/main/rs/state.rsh
index b7fb925..d47e4e9 100644
--- a/app/src/main/rs/state.rsh
+++ b/app/src/main/rs/state.rsh
@@ -17,7 +17,7 @@ limitations under the License.
 #ifndef STATE_RSH
 #define STATE_RSH
 
-static ema_t avg_power, leader_lowpass;
+static ema_t avg_amplitude, leader_lowpass;
 static ddc_t cnt_ddc, dat_ddc;
 static fmd_t cnt_fmd, dat_fmd;
 static int current_decoder;