1 files changed, 19 insertions, 5 deletions

diff --git a/apps/dsp.c b/apps/dsp.c
index ca494e553f..9e410f879a 100644
--- a/apps/dsp.c
+++ b/apps/dsp.c
@@ -787,13 +787,27 @@ void dsp_set_crossfeed_direct_gain(int gain)
         crossfeed_data.gain = 0x7fffffff;
 }
 
+/* Both gains should be below 0 dB (when inverted) */
 void dsp_set_crossfeed_cross_params(long lf_gain, long hf_gain, long cutoff)
 {
-    long g1 = get_replaygain_int(lf_gain * -10) << 3;
-    long g2 = get_replaygain_int(hf_gain * -10) << 3;
-
-    filter_shelf_coefs(0xffffffff/NATIVE_FREQUENCY*cutoff, g1, g2,
-                       crossfeed_data.coefs);
+    int32_t *c = crossfeed_data.coefs;
+    long scaler = get_replaygain_int(lf_gain * -10) << 7;
+
+    cutoff = 0xffffffff/NATIVE_FREQUENCY*cutoff;
+    hf_gain -= lf_gain;
+    /* Divide cutoff by sqrt(10^(-hf_gain/20)) to place cutoff at the -3 dB
+     * point instead of shelf midpoint. This is for compatibility with the old
+     * crossfeed shelf filter and should be removed if crossfeed settings are
+     * ever made incompatible for any other good reason.
+     */
+    cutoff = DIV64(cutoff, get_replaygain_int(-hf_gain*5), 24);
+    filter_shelf_coefs(cutoff, -hf_gain, false, c);
+    /* Scale coefs by LF gain and shift them to s0.31 format. We have no gains
+     * over 1 and can do this safely
+     */
+    c[0] = FRACMUL_SHL(c[0], scaler, 4);
+    c[1] = FRACMUL_SHL(c[1], scaler, 4);
+    c[2] <<= 4;
 }
 
 /* Combine all gains to a global gain. */