diff --git a/content/media/video/public/nsMediaDecoder.h b/content/media/video/public/nsMediaDecoder.h
index 026a59cef2fa..c06dc466d722 100644
--- a/content/media/video/public/nsMediaDecoder.h
+++ b/content/media/video/public/nsMediaDecoder.h
@@ -244,12 +244,14 @@ protected:
   // Stop progress information timer.
   nsresult StopProgress();
 
-  // Set the RGB width, height and framerate. Ownership of the passed RGB
-  // buffer is transferred to the decoder.  This is the only nsMediaDecoder
-  // method that may be called from threads other than the main thread.
+  // Set the RGB width, height, pixel aspect ratio, and framerate.
+  // Ownership of the passed RGB buffer is transferred to the decoder.
+  // This is the only nsMediaDecoder method that may be called from
+  // threads other than the main thread.
   void SetRGBData(PRInt32 aWidth,
                   PRInt32 aHeight,
                   float aFramerate,
+                  float aAspectRatio,
                   unsigned char* aRGBBuffer);
 
 protected:
@@ -295,6 +297,9 @@ protected:
   // expressed in numbers of frames per second.
   float mFramerate;
 
+  // Pixel aspect ratio (ratio of the pixel width to pixel height)
+  float mAspectRatio;
+
   // Has our size changed since the last repaint?
   PRPackedBool mSizeChanged;
 
diff --git a/content/media/video/src/nsMediaDecoder.cpp b/content/media/video/src/nsMediaDecoder.cpp
index 258db168d836..97e5225ab56b 100644
--- a/content/media/video/src/nsMediaDecoder.cpp
+++ b/content/media/video/src/nsMediaDecoder.cpp
@@ -72,6 +72,7 @@ nsMediaDecoder::nsMediaDecoder() :
   mDataTime(),
   mVideoUpdateLock(nsnull),
   mFramerate(0.0),
+  mAspectRatio(1.0),
   mSizeChanged(PR_FALSE),
   mShuttingDown(PR_FALSE),
   mStopping(PR_FALSE)
@@ -114,6 +115,14 @@ nsresult nsMediaDecoder::InitLogger()
   return NS_OK;
 }
 
+static PRInt32 ConditionDimension(float aValue, PRInt32 aDefault)
+{
+  // This will exclude NaNs and infinities
+  if (aValue >= 1.0 && aValue <= 10000.0)
+    return PRInt32(NS_round(aValue));
+  return aDefault;
+}
+
 void nsMediaDecoder::Invalidate()
 {
   if (!mElement)
@@ -124,7 +133,20 @@ void nsMediaDecoder::Invalidate()
   {
     nsAutoLock lock(mVideoUpdateLock);
     if (mSizeChanged) {
-      mElement->UpdateMediaSize(nsIntSize(mRGBWidth, mRGBHeight));
+      nsIntSize scaledSize(mRGBWidth, mRGBHeight);
+      // Apply the aspect ratio to produce the intrinsic size we report
+      // to the element.
+      if (mAspectRatio > 1.0) {
+        // Increase the intrinsic width
+        scaledSize.width =
+          ConditionDimension(mAspectRatio*scaledSize.width, scaledSize.width);
+      } else {
+        // Increase the intrinsic height
+        scaledSize.height =
+          ConditionDimension(scaledSize.height/mAspectRatio, scaledSize.height);
+      }
+      mElement->UpdateMediaSize(scaledSize);
+
       mSizeChanged = PR_FALSE;
       if (frame) {
         nsPresContext* presContext = frame->PresContext();      
@@ -200,13 +222,16 @@ nsresult nsMediaDecoder::StopProgress()
   return rv;
 }
 
-void nsMediaDecoder::SetRGBData(PRInt32 aWidth, PRInt32 aHeight, float aFramerate, unsigned char* aRGBBuffer)
+void nsMediaDecoder::SetRGBData(PRInt32 aWidth, PRInt32 aHeight, float aFramerate,
+                                float aAspectRatio, unsigned char* aRGBBuffer)
 {
   nsAutoLock lock(mVideoUpdateLock);
 
-  if (mRGBWidth != aWidth || mRGBHeight != aHeight) {
+  if (mRGBWidth != aWidth || mRGBHeight != aHeight ||
+      mAspectRatio != aAspectRatio) {
     mRGBWidth = aWidth;
     mRGBHeight = aHeight;
+    mAspectRatio = aAspectRatio;
     mSizeChanged = PR_TRUE;
   }
   mFramerate = aFramerate;
diff --git a/content/media/video/src/nsOggDecoder.cpp b/content/media/video/src/nsOggDecoder.cpp
index 2cca639eecf7..45edb99e95d5 100644
--- a/content/media/video/src/nsOggDecoder.cpp
+++ b/content/media/video/src/nsOggDecoder.cpp
@@ -473,6 +473,7 @@ private:
   // They are only accessed from the decoder thread.
   PRInt32 mVideoTrack;
   float   mFramerate;
+  float   mAspectRatio;
 
   // Audio data. These are initially set when the metadata is loaded.
   // They are only accessed from the decoder thread.
@@ -660,6 +661,7 @@ nsOggDecodeStateMachine::nsOggDecodeStateMachine(nsOggDecoder* aDecoder) :
   mCallbackPeriod(1.0),
   mVideoTrack(-1),
   mFramerate(0.0),
+  mAspectRatio(1.0),
   mAudioRate(0),
   mAudioChannels(0),
   mAudioTrack(-1),
@@ -933,7 +935,8 @@ void nsOggDecodeStateMachine::PlayVideo(FrameData* aFrame)
 
     oggplay_yuv2bgra(&yuv, &rgb);
 
-    mDecoder->SetRGBData(aFrame->mVideoWidth, aFrame->mVideoHeight, mFramerate, buffer.forget());
+    mDecoder->SetRGBData(aFrame->mVideoWidth, aFrame->mVideoHeight,
+                         mFramerate, mAspectRatio, buffer.forget());
   }
 }
 
@@ -1550,10 +1553,18 @@ void nsOggDecodeStateMachine::LoadOggHeaders(nsChannelReader* aReader)
         mCallbackPeriod = 1.0 / mFramerate;
         LOG(PR_LOG_DEBUG, ("Frame rate: %f", mFramerate));
 
+        int aspectd, aspectn;
+        // this can return E_OGGPLAY_UNINITIALIZED if the video has
+        // no aspect ratio data. We assume 1.0 in that case.
+        OggPlayErrorCode r =
+          oggplay_get_video_aspect_ratio(mPlayer, i, &aspectd, &aspectn);
+        mAspectRatio = r == E_OGGPLAY_OK && aspectd > 0 ?
+            float(aspectn)/float(aspectd) : 1.0;
+
         int y_width;
         int y_height;
         oggplay_get_video_y_size(mPlayer, i, &y_width, &y_height);
-        mDecoder->SetRGBData(y_width, y_height, mFramerate, nsnull);
+        mDecoder->SetRGBData(y_width, y_height, mFramerate, mAspectRatio, nsnull);
       }
       else if (mAudioTrack == -1 && oggplay_get_track_type(mPlayer, i) == OGGZ_CONTENT_VORBIS) {
         mAudioTrack = i;