Add an IIR filter option for UHJ encoding/decoding

This uses the reversed-allpass trick to maintain linear phase. with a 256-
sample look-ahead/delay to minimize distortion. This should better preserve low
frequencies while maintaining a proper phase response.

1 files changed, 4 insertions, 2 deletions

diff --git a/alc/alc.cpp b/alc/alc.cpp
index e89ad598..1f70569a 100644
--- a/alc/alc.cpp
+++ b/alc/alc.cpp
@@ -1148,9 +1148,11 @@ void alc_initconfig(void)
     if(auto uhjfiltopt = ConfigValueStr(nullptr, "uhj", "filter"))
     {
         if(al::strcasecmp(uhjfiltopt->c_str(), "fir256") == 0)
-            UhjQuality = UhjLengthLq;
+            UhjQuality = UhjQualityType::FIR256;
         else if(al::strcasecmp(uhjfiltopt->c_str(), "fir512") == 0)
-            UhjQuality = UhjLengthHq;
+            UhjQuality = UhjQualityType::FIR512;
+        else if(al::strcasecmp(uhjfiltopt->c_str(), "iir") == 0)
+            UhjQuality = UhjQualityType::IIR;
         else
             WARN("Unsupported uhj/filter: %s\n", uhjfiltopt->c_str());
     }