--- a/dom/media/omx/OMXCodecDescriptorUtil.cpp
+++ b/dom/media/omx/OMXCodecDescriptorUtil.cpp
@@ -79,18 +79,18 @@ struct AVCParamSet {
     return mSize + 2; // 2 more bytes for length value.
   }
 
   // Append 2 bytes length value and NAL unit bitstream to aOutputBuf.
   void AppendTo(nsTArray<uint8_t>* aOutputBuf)
   {
     // 2 bytes length value.
     uint8_t size[] = {
-      (mSize & 0xFF00) >> 8, // MSB.
-      mSize & 0x00FF,        // LSB.
+      uint8_t((mSize & 0xFF00) >> 8), // MSB.
+      uint8_t(mSize & 0x00FF),        // LSB.
     };
     aOutputBuf->AppendElements(size, sizeof(size));
 
     aOutputBuf->AppendElements(mPtr, mSize);
   }
 
   const uint8_t* mPtr; // Pointer to NAL unit.
   const size_t mSize;  // NAL unit length in bytes.

--- a/dom/media/omx/OMXCodecWrapper.cpp
+++ b/dom/media/omx/OMXCodecWrapper.cpp
@@ -490,20 +490,20 @@ OMXVideoEncoder::AppendFrame(nsTArray<ui
 
   if (mBlobFormat == BlobFormat::AVC_NAL) {
     // Append NAL format data without modification.
     aOutputBuf->AppendElements(aData, aSize);
     return;
   }
   // Replace start code with data length.
   uint8_t length[] = {
-    (aSize >> 24) & 0xFF,
-    (aSize >> 16) & 0xFF,
-    (aSize >> 8) & 0xFF,
-    aSize & 0xFF,
+    uint8_t((aSize >> 24) & 0xFF),
+    uint8_t((aSize >> 16) & 0xFF),
+    uint8_t((aSize >> 8) & 0xFF),
+    uint8_t(aSize & 0xFF),
   };
   aOutputBuf->AppendElements(length, sizeof(length));
   aOutputBuf->AppendElements(aData + sizeof(length), aSize);
 }
 
 // MediaCodec::setParameters() is available only after API level 18.
 #if ANDROID_VERSION >= 18
 nsresult
@@ -903,24 +903,24 @@ OMXAudioEncoder::AppendDecoderConfig(nsT
   NS_ENSURE_TRUE(csdSize == 2, ERROR_MALFORMED);
   // Encoder output must be consistent with kAACFrameDuration:
   // 14th bit (frame length flag) == 0 => 1024 (kAACFrameDuration) samples.
   NS_ENSURE_TRUE((aData->data()[1] & 0x04) == 0, ERROR_MALFORMED);
 
   // Decoder config descriptor
   const uint8_t decConfig[] = {
     0x04,                   // Decoder config descriptor tag.
-    15 + csdSize,           // Size: following bytes + csd size.
+    uint8_t(15 + csdSize),  // Size: following bytes + csd size.
     0x40,                   // Object type: MPEG-4 audio.
     0x15,                   // Stream type: audio, reserved: 1.
     0x00, 0x03, 0x00,       // Buffer size: 768 (kAACFrameSize).
     0x00, 0x01, 0x77, 0x00, // Max bitrate: 96000 (kAACBitrate).
     0x00, 0x01, 0x77, 0x00, // Avg bitrate: 96000 (kAACBitrate).
     0x05,                   // Decoder specific descriptor tag.
-    csdSize,                // Data size.
+    uint8_t(csdSize),       // Data size.
   };
   // SL config descriptor.
   const uint8_t slConfig[] = {
     0x06, // SL config descriptor tag.
     0x01, // Size.
     0x02, // Fixed value.
   };