diff --git a/dom/media/fmp4/MP4Decoder.cpp b/dom/media/fmp4/MP4Decoder.cpp
index 25ad3adb21bc..0bdd9faa36e5 100644
--- a/dom/media/fmp4/MP4Decoder.cpp
+++ b/dom/media/fmp4/MP4Decoder.cpp
@@ -182,11 +182,33 @@ MP4Decoder::IsEnabled()
   return Preferences::GetBool("media.mp4.enabled");
 }
 
+// sTestH264ExtraData represents the content of the avcC atom found in
+// an AVC1 h264 video. It contains the H264 SPS and PPS NAL.
+// the structure of the avcC atom is as follow:
+// write(0x1);  // version, always 1
+// write(sps[0].data[1]); // profile
+// write(sps[0].data[2]); // compatibility
+// write(sps[0].data[3]); // level
+// write(0xFC | 3); // reserved (6 bits), NULA length size - 1 (2 bits)
+// write(0xE0 | 1); // reserved (3 bits), num of SPS (5 bits)
+// write_word(sps[0].size); // 2 bytes for length of SPS
+// for(size_t i=0 ; i < sps[0].size ; ++i)
+//   write(sps[0].data[i]); // data of SPS
+// write(&b, pps.size());  // num of PPS
+// for(size_t i=0 ; i < pps.size() ; ++i) {
+//   write_word(pps[i].size);  // 2 bytes for length of PPS
+//   for(size_t j=0 ; j < pps[i].size ; ++j)
+//     write(pps[i].data[j]);  // data of PPS
+//   }
+// }
+// here we have a h264 Baseline, 640x360
+// We use a 640x360 extradata, as some video framework (Apple VT) will never
+// attempt to use hardware decoding for small videos.
 static const uint8_t sTestH264ExtraData[] = {
-  0x01, 0x64, 0x00, 0x0a, 0xff, 0xe1, 0x00, 0x17, 0x67, 0x64,
-  0x00, 0x0a, 0xac, 0xd9, 0x44, 0x26, 0x84, 0x00, 0x00, 0x03,
-  0x00, 0x04, 0x00, 0x00, 0x03, 0x00, 0xc8, 0x3c, 0x48, 0x96,
-  0x58, 0x01, 0x00, 0x06, 0x68, 0xeb, 0xe3, 0xcb, 0x22, 0xc0
+  0x01, 0x42, 0xc0, 0x1e, 0xff, 0xe1, 0x00, 0x17, 0x67, 0x42,
+  0xc0, 0x1e, 0xbb, 0x40, 0x50, 0x17, 0xfc, 0xb8, 0x08, 0x80,
+  0x00, 0x00, 0x32, 0x00, 0x00, 0x0b, 0xb5, 0x07, 0x8b, 0x17,
+  0x50, 0x01, 0x00, 0x04, 0x68, 0xce, 0x32, 0xc8
 };
 
 static already_AddRefed<MediaDataDecoder>
@@ -197,8 +219,8 @@ CreateTestH264Decoder(layers::LayersBackend aBackend,
   aConfig.mId = 1;
   aConfig.mDuration = 40000;
   aConfig.mMediaTime = 0;
-  aConfig.mDisplay = nsIntSize(64, 64);
-  aConfig.mImage = nsIntRect(0, 0, 64, 64);
+  aConfig.mDisplay = nsIntSize(640, 360);
+  aConfig.mImage = nsIntRect(0, 0, 640, 360);
   aConfig.mExtraData = new MediaByteBuffer();
   aConfig.mExtraData->AppendElements(sTestH264ExtraData,
                                      MOZ_ARRAY_LENGTH(sTestH264ExtraData));