diff --git a/graphics/mapper/4.0/vts/functional/VtsHalGraphicsMapperV4_0TargetTest.cpp b/graphics/mapper/4.0/vts/functional/VtsHalGraphicsMapperV4_0TargetTest.cpp
index 6cc5e34326..82dbeb9c20 100644
--- a/graphics/mapper/4.0/vts/functional/VtsHalGraphicsMapperV4_0TargetTest.cpp
+++ b/graphics/mapper/4.0/vts/functional/VtsHalGraphicsMapperV4_0TargetTest.cpp
@@ -221,7 +221,7 @@ class GraphicsMapperHidlTest
                     case PlaneLayoutComponentType::Y:
                         ASSERT_EQ(nullptr, outYCbCr->y);
                         ASSERT_EQ(8, planeLayoutComponent.sizeInBits);
-                        ASSERT_EQ(32, planeLayout.sampleIncrementInBits);
+                        ASSERT_EQ(8, planeLayout.sampleIncrementInBits);
                         outYCbCr->y = tmpData;
                         outYCbCr->ystride = planeLayout.strideInBytes;
                         break;
@@ -569,15 +569,21 @@ TEST_P(GraphicsMapperHidlTest, Lock_YCBCR_420_888) {
     auto cStride = yCbCr.cstride;
     auto chromaStep = yCbCr.chroma_step;
 
+    constexpr uint32_t kCbCrSubSampleFactor = 2;
+
     for (uint32_t y = 0; y < info.height; y++) {
         for (uint32_t x = 0; x < info.width; x++) {
             auto val = static_cast<uint8_t>(info.height * y + x);
 
             yData[yStride * y + x] = val;
 
-            if (y % chromaStep && x % chromaStep == 0) {
-                cbData[cStride * y / chromaStep + x / chromaStep] = val;
-                crData[cStride * y / chromaStep + x / chromaStep] = val;
+            if (y % kCbCrSubSampleFactor && x % kCbCrSubSampleFactor == 0) {
+                uint32_t subSampleX = x / kCbCrSubSampleFactor;
+                uint32_t subSampleY = y / kCbCrSubSampleFactor;
+                auto subSampleVal = static_cast<uint8_t>(info.height * subSampleY + subSampleX);
+
+                cbData[cStride * subSampleY + chromaStep * subSampleX] = subSampleVal;
+                crData[cStride * subSampleY + chromaStep * subSampleX] = subSampleVal;
             }
         }
     }
@@ -599,9 +605,13 @@ TEST_P(GraphicsMapperHidlTest, Lock_YCBCR_420_888) {
 
             EXPECT_EQ(val, yData[yStride * y + x]);
 
-            if (y % chromaStep == 0 && x % chromaStep == 0) {
-                EXPECT_EQ(val, cbData[cStride * y / chromaStep + x / chromaStep]);
-                EXPECT_EQ(val, crData[cStride * y / chromaStep + x / chromaStep]);
+            if (y % kCbCrSubSampleFactor == 0 && x % kCbCrSubSampleFactor == 0) {
+                uint32_t subSampleX = x / kCbCrSubSampleFactor;
+                uint32_t subSampleY = y / kCbCrSubSampleFactor;
+                auto subSampleVal = static_cast<uint8_t>(info.height * subSampleY + subSampleX);
+
+                EXPECT_EQ(subSampleVal, cbData[cStride * subSampleY + chromaStep * subSampleX]);
+                EXPECT_EQ(subSampleVal, crData[cStride * subSampleY + chromaStep * subSampleX]);
             }
         }
     }