From 4d224f5e212f236da91199277ce302f7bd7030fa Mon Sep 17 00:00:00 2001
From: George Norton <george_norton_uk@hotmail.com>
Date: Sun, 18 Jun 2023 00:32:20 +0100
Subject: [PATCH] Reset memory on filter type change..

---
 firmware/code/configuration_manager.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/firmware/code/configuration_manager.c b/firmware/code/configuration_manager.c
index 7b0f37b..bc9a020 100644
--- a/firmware/code/configuration_manager.c
+++ b/firmware/code/configuration_manager.c
@@ -170,9 +170,17 @@ void apply_filter_configuration(filter_configuration_tlv *filters) {
     }
 
     if (type_changed) {
+        fix16_t left[2] = { bqf_filters_mem_left[0].x_2, bqf_filters_mem_left[0].x_1 };
+        fix16_t right[2] = { bqf_filters_mem_right[0].x_2, bqf_filters_mem_right[0].x_1 };
         for (int i=0; i<MAX_FILTER_STAGES; i++) {
             bqf_memreset(&bqf_filters_mem_left[i]);
             bqf_memreset(&bqf_filters_mem_right[i]);
+            // The memory structure stores the last 2 input samples, we can replay them into
+            // the new filter rather than starting again from scratch.
+            left[0] = bqf_transform(left[0], &bqf_filters_left[i], &bqf_filters_mem_left[i]);
+            left[1] = bqf_transform(left[1], &bqf_filters_left[i], &bqf_filters_mem_left[i]);
+            right[0] = bqf_transform(right[0], &bqf_filters_left[i], &bqf_filters_mem_left[i]);
+            right[1] = bqf_transform(right[1], &bqf_filters_left[i], &bqf_filters_mem_left[i]);
         }
     }
 }