Make `--tune=iq` use the all intra luma QM level formula

Using the SSIMULACRA 2 luma QM formula can result in an image that
can visually look too soft or blurry in some cases, especially at
low to mid quality levels.

`--tune=ssimulacra2` will continue using the SSIMULACRA 2 formula.

Bug: aomedia:401234702
Change-Id: I60778359becf263b925468813be3de6c242c3f85

av1/av1_cx_iface.c

diff --git a/av1/av1_cx_iface.c b/av1/av1_cx_iface.c
index 79908ec..97bc198 100644
--- a/av1/av1_cx_iface.c
+++ b/av1/av1_cx_iface.c
@@ -1825,11 +1825,11 @@
     // Enable QMs as they've been found to be beneficial for images, when used
     // with alternative QM formulas:
     // - aom_get_qmlevel_allintra()
-    // - aom_get_qmlevel_luma_iq()
-    // - aom_get_qmlevel_444_chroma_iq()
+    // - aom_get_qmlevel_luma_ssimulacra2()
+    // - aom_get_qmlevel_444_chroma()
     extra_cfg->enable_qm = 1;
-    extra_cfg->qm_min = QM_FIRST_IQ;
-    extra_cfg->qm_max = QM_LAST_IQ;
+    extra_cfg->qm_min = QM_FIRST_IQ_SSIMULACRA2;
+    extra_cfg->qm_max = QM_LAST_IQ_SSIMULACRA2;
     // We can turn on loop filter sharpness, as frames do not have to serve as
     // references to others.
     extra_cfg->sharpness = 7;

av1/common/quant_common.h

diff --git a/av1/common/quant_common.h b/av1/common/quant_common.h
index 129c5c2..965a746 100644
--- a/av1/common/quant_common.h
+++ b/av1/common/quant_common.h
@@ -38,8 +38,8 @@
 #define DEFAULT_QM_LAST 9
 #define DEFAULT_QM_FIRST_ALLINTRA 4
 #define DEFAULT_QM_LAST_ALLINTRA 10
-#define QM_FIRST_IQ 2
-#define QM_LAST_IQ 10
+#define QM_FIRST_IQ_SSIMULACRA2 2
+#define QM_LAST_IQ_SSIMULACRA2 10
 #define LOSSLESS_Q_STEP 4  // this should equal to dc/ac_qlookup_QTX[0]
 
 struct AV1Common;
@@ -96,7 +96,7 @@
   return clamp(qm_level, first, last);
 }
 
-// Luma QM levels tuned for image quality (IQ)
+// Luma QM levels tuned for SSIMULACRA 2
 // This formula was empirically derived by encoding Daala's subset1 validation
 // testset for each QP/QM tuple, and building a convex hull that maximizes
 // SSIMULACRA 2 scores, and a final subjective visual quality pass as a quick
@@ -108,7 +108,8 @@
 // both set below or above this range.
 // For more information on quantization matrices, please refer to
 // https://arxiv.org/pdf/2008.06091, section F.
-static inline int aom_get_qmlevel_luma_iq(int qindex, int first, int last) {
+static inline int aom_get_qmlevel_luma_ssimulacra2(int qindex, int first,
+                                                   int last) {
   int qm_level = 0;
 
   if (qindex <= 40) {
@@ -134,7 +135,7 @@
   return clamp(qm_level, first, last);
 }
 
-// Chroma QM levels for 4:4:4 subsampling tuned for image quality (IQ)
+// Chroma QM levels for 4:4:4 subsampling used for SSIMULACRA 2 and IQ tunings
 // This formula was empirically derived by encoding Daala's subset1 validation
 // testset for each QP/QM tuple, and building a convex hull that maximizes
 // SSIMULACRA 2 scores, and a final subjective visual quality pass as a quick
@@ -146,8 +147,7 @@
 // both set below or above this range.
 // For more information on quantization matrices, please refer to
 // https://arxiv.org/pdf/2008.06091, section F.
-static inline int aom_get_qmlevel_444_chroma_iq(int qindex, int first,
-                                                int last) {
+static inline int aom_get_qmlevel_444_chroma(int qindex, int first, int last) {
   int chroma_qm_level = 0;
 
   if (qindex <= 12) {

av1/encoder/av1_quantize.c

diff --git a/av1/encoder/av1_quantize.c b/av1/encoder/av1_quantize.c
index 0615224..1f962c3 100644
--- a/av1/encoder/av1_quantize.c
+++ b/av1/encoder/av1_quantize.c
@@ -971,8 +971,12 @@
 
   if (is_allintra) {
     if (tuning == AOM_TUNE_IQ || tuning == AOM_TUNE_SSIMULACRA2) {
-      // Use luma QM formula specifically tailored for tune IQ
-      get_luma_qmlevel = aom_get_qmlevel_luma_iq;
+      if (tuning == AOM_TUNE_SSIMULACRA2) {
+        // Use luma QM formula specifically tailored for tune SSIMULACRA2
+        get_luma_qmlevel = aom_get_qmlevel_luma_ssimulacra2;
+      } else {
+        get_luma_qmlevel = aom_get_qmlevel_allintra;
+      }
 
       if (cm->seq_params->subsampling_x == 0 &&
           cm->seq_params->subsampling_y == 0) {
@@ -980,7 +984,7 @@
         // compared to 4:2:0 (2x on each dimension). This means the encoder
         // should use lower chroma QM levels that more closely match the scaling
         // of an equivalent 4:2:0 chroma QM.
-        get_chroma_qmlevel = aom_get_qmlevel_444_chroma_iq;
+        get_chroma_qmlevel = aom_get_qmlevel_444_chroma;
       } else {
         // For all other chroma subsampling modes, use the all intra QM formula
         get_chroma_qmlevel = aom_get_qmlevel_allintra;