Smooth change gain on correction for FT8 TX

src/audio.c

@@ -194,6 +194,26 @@ void audio_gain_db(int16_t *buf, size_t samples, float gain, int16_t *out) {
     }
 }
 
+void audio_gain_db_transition(int16_t *buf, size_t samples, float gain1, float gain2, int16_t *out) {
+    float scale1 = exp10f(gain1 / 10.0f);
+    float scale2 = exp10f(gain2 / 10.0f);
+    float scale;
+    for (uint16_t i = 0; i < samples; i++) {
+        scale = scale1 + i * (scale2 - scale1) / samples;
+        int32_t x = buf[i] * scale;
+
+        if (x > 32767) {
+            x = 32767;
+        }
+
+        if (x < -32767) {
+            x = -32767;
+        }
+
+        out[i] = x;
+    }
+}
+
 void audio_play_en(bool on) {
     if (on) {
         x6100_control_hmic_set(0);

src/audio.h

@@ -20,3 +20,4 @@ void audio_play_wait();
 void audio_play_en(bool on);
 
 void audio_gain_db(int16_t *buf, size_t samples, float gain, int16_t *out);
+void audio_gain_db_transition(int16_t *buf, size_t samples, float gain1, float gain2, int16_t *out);

src/dialog_ft8.c

@@ -1317,6 +1317,7 @@ static void tx_worker() {
     float target_pwr = LV_MIN(params.pwr, MAX_PWR);
     float base_gain_scale = -8.2f + log10f(target_pwr) * 5;
     float gain_scale = base_gain_scale + params.ft8_output_gain_offset.x;
+    float prev_gain_scale = gain_scale;
     size_t counter = 0;
 
     while (true) {
@@ -1330,7 +1331,13 @@ static void tx_worker() {
             break;
         }
         part = LV_MIN(1024 * 2, n_samples);
-        audio_gain_db(ptr, part, gain_scale, ptr);
+        if (gain_scale == prev_gain_scale) {
+            audio_gain_db(ptr, part, gain_scale, ptr);
+        } else {
+            // Smooth change gain
+            audio_gain_db_transition(ptr, part, prev_gain_scale, gain_scale, ptr);
+            prev_gain_scale = gain_scale;
+        }
         audio_play(ptr, part);
 
         n_samples -= part;