diff --git a/patches/config.json b/patches/config.json
index e9a2297ba1..74b5339587 100644
--- a/patches/config.json
+++ b/patches/config.json
@@ -13,5 +13,7 @@
 
   "src/electron/patches/Mantle": "src/third_party/squirrel.mac/vendor/Mantle",
 
-  "src/electron/patches/ReactiveObjC": "src/third_party/squirrel.mac/vendor/ReactiveObjC"
+  "src/electron/patches/ReactiveObjC": "src/third_party/squirrel.mac/vendor/ReactiveObjC",
+
+  "src/electron/patches/libgav1": "src/third_party/libgav1/src"
 }
diff --git a/patches/libgav1/.patches b/patches/libgav1/.patches
new file mode 100644
index 0000000000..ce9819d511
--- /dev/null
+++ b/patches/libgav1/.patches
@@ -0,0 +1 @@
+arm_dsp_fix_8bpp_dct64_neon.patch
diff --git a/patches/libgav1/arm_dsp_fix_8bpp_dct64_neon.patch b/patches/libgav1/arm_dsp_fix_8bpp_dct64_neon.patch
new file mode 100644
index 0000000000..be46a4993b
--- /dev/null
+++ b/patches/libgav1/arm_dsp_fix_8bpp_dct64_neon.patch
@@ -0,0 +1,98 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Scott LaVarnway <slavarnway@google.com>
+Date: Sat, 14 Aug 2021 09:35:39 -0700
+Subject: arm,dsp: Fix 8bpp Dct64_NEON().
+
+When building with clang (-march=armv8.2), an "off by one" error was detected. For now,
+disable the fast butterfly.
+
+PiperOrigin-RevId: 390805568
+Change-Id: I9749a665b8235ec0f0dcbca46b284223c95af2a9
+
+diff --git a/src/dsp/arm/inverse_transform_neon.cc b/src/dsp/arm/inverse_transform_neon.cc
+index 4af8cf7ff68810016cc777719f84888fe00abb1f..0371cd54b3d0f64040a67d8c776270637137134b 100644
+--- a/src/dsp/arm/inverse_transform_neon.cc
++++ b/src/dsp/arm/inverse_transform_neon.cc
+@@ -388,6 +388,33 @@ LIBGAV1_ALWAYS_INLINE void ButterflyRotation_FirstIsZero(int16x8_t* a,
+                                                          int16x8_t* b,
+                                                          const int angle,
+                                                          const bool flip) {
++#if defined(__ARM_FEATURE_QRDMX) && defined(__aarch64__) && \
++    defined(__clang__)  // ARM v8.1-A
++  // Clang optimizes vqrdmulhq_n_s16 and vqsubq_s16 (in HadamardRotation) into
++  // vqrdmlshq_s16 resulting in an "off by one" error. For now, do not use
++  // vqrdmulhq_n_s16().
++  const int16_t cos128 = Cos128(angle);
++  const int16_t sin128 = Sin128(angle);
++  const int32x4_t x0 = vmull_n_s16(vget_low_s16(*b), -sin128);
++  const int32x4_t y0 = vmull_n_s16(vget_low_s16(*b), cos128);
++  const int16x4_t x1 = vqrshrn_n_s32(x0, 12);
++  const int16x4_t y1 = vqrshrn_n_s32(y0, 12);
++
++  const int32x4_t x0_hi = vmull_n_s16(vget_high_s16(*b), -sin128);
++  const int32x4_t y0_hi = vmull_n_s16(vget_high_s16(*b), cos128);
++  const int16x4_t x1_hi = vqrshrn_n_s32(x0_hi, 12);
++  const int16x4_t y1_hi = vqrshrn_n_s32(y0_hi, 12);
++
++  const int16x8_t x = vcombine_s16(x1, x1_hi);
++  const int16x8_t y = vcombine_s16(y1, y1_hi);
++  if (flip) {
++    *a = y;
++    *b = x;
++  } else {
++    *a = x;
++    *b = y;
++  }
++#else
+   const int16_t cos128 = Cos128(angle);
+   const int16_t sin128 = Sin128(angle);
+   // For this function, the max value returned by Sin128() is 4091, which fits
+@@ -403,12 +430,40 @@ LIBGAV1_ALWAYS_INLINE void ButterflyRotation_FirstIsZero(int16x8_t* a,
+     *a = x;
+     *b = y;
+   }
++#endif
+ }
+ 
+ LIBGAV1_ALWAYS_INLINE void ButterflyRotation_SecondIsZero(int16x8_t* a,
+                                                           int16x8_t* b,
+                                                           const int angle,
+                                                           const bool flip) {
++#if defined(__ARM_FEATURE_QRDMX) && defined(__aarch64__) && \
++    defined(__clang__)  // ARM v8.1-A
++  // Clang optimizes vqrdmulhq_n_s16 and vqsubq_s16 (in HadamardRotation) into
++  // vqrdmlshq_s16 resulting in an "off by one" error. For now, do not use
++  // vqrdmulhq_n_s16().
++  const int16_t cos128 = Cos128(angle);
++  const int16_t sin128 = Sin128(angle);
++  const int32x4_t x0 = vmull_n_s16(vget_low_s16(*a), cos128);
++  const int32x4_t y0 = vmull_n_s16(vget_low_s16(*a), sin128);
++  const int16x4_t x1 = vqrshrn_n_s32(x0, 12);
++  const int16x4_t y1 = vqrshrn_n_s32(y0, 12);
++
++  const int32x4_t x0_hi = vmull_n_s16(vget_high_s16(*a), cos128);
++  const int32x4_t y0_hi = vmull_n_s16(vget_high_s16(*a), sin128);
++  const int16x4_t x1_hi = vqrshrn_n_s32(x0_hi, 12);
++  const int16x4_t y1_hi = vqrshrn_n_s32(y0_hi, 12);
++
++  const int16x8_t x = vcombine_s16(x1, x1_hi);
++  const int16x8_t y = vcombine_s16(y1, y1_hi);
++  if (flip) {
++    *a = y;
++    *b = x;
++  } else {
++    *a = x;
++    *b = y;
++  }
++#else
+   const int16_t cos128 = Cos128(angle);
+   const int16_t sin128 = Sin128(angle);
+   const int16x8_t x = vqrdmulhq_n_s16(*a, cos128 << 3);
+@@ -420,6 +475,7 @@ LIBGAV1_ALWAYS_INLINE void ButterflyRotation_SecondIsZero(int16x8_t* a,
+     *a = x;
+     *b = y;
+   }
++#endif
+ }
+ 
+ LIBGAV1_ALWAYS_INLINE void HadamardRotation(int16x8_t* a, int16x8_t* b,