diff -up firefox-79.0/dom/media/platforms/ffmpeg/FFmpegVideoDecoder.cpp.mozilla-1656436 firefox-79.0/dom/media/platforms/ffmpeg/FFmpegVideoDecoder.cpp
--- firefox-79.0/dom/media/platforms/ffmpeg/FFmpegVideoDecoder.cpp.mozilla-1656436	2020-08-04 13:31:49.476663242 +0200
+++ firefox-79.0/dom/media/platforms/ffmpeg/FFmpegVideoDecoder.cpp	2020-08-04 13:32:28.201448682 +0200
@@ -766,6 +766,11 @@ MediaResult FFmpegVideoDecoder<LIBAV_VER
     mDMABufSurfaces.EmplaceBack(surface, mLib);
     surfaceWrapper = &(mDMABufSurfaces[mDMABufSurfaces.Length() - 1]);
   } else {
+    // Release VAAPI surface data before we reuse it.
+    if (mVAAPIDeviceContext) {
+      surfaceWrapper->ReleaseVAAPIData();
+    }
+
     surface = surfaceWrapper->GetDMABufSurface();
     bool ret;
 
diff -up firefox-79.0/widget/gtk/DMABufSurface.cpp.mozilla-1656436 firefox-79.0/widget/gtk/DMABufSurface.cpp
--- firefox-79.0/widget/gtk/DMABufSurface.cpp.mozilla-1656436	2020-08-04 13:31:49.477663237 +0200
+++ firefox-79.0/widget/gtk/DMABufSurface.cpp	2020-08-04 13:33:07.666230023 +0200
@@ -744,7 +744,8 @@ bool DMABufSurfaceYUV::UpdateYUVData(con
     return false;
   }
   if (mDmabufFds[0] >= 0) {
-    ReleaseSurface();
+    NS_WARNING("DMABufSurfaceYUV is already created!");
+    return false;
   }
 
   mSurfaceFormat = gfx::SurfaceFormat::NV12;