Bug 1374774: P9. Only look for SPS changes in stream format change detection. r=gerald

All decoders appear capable of handling content change when just new PPS appears.
So we restrict the test to SPS changes.

MozReview-Commit-ID: LPSfMaTIj6C

--HG--
extra : rebase_source : 524316ba61ffff1549a0828685ac657abe687426

media/libstagefright/binding/H264.cpp

@@ -919,28 +919,51 @@ H264::ExtractExtraData(const mozilla::MediaRawData* aSample)
 
 /* static */ bool
 H264::HasSPS(const mozilla::MediaByteBuffer* aExtraData)
+{
+  return NumSPS(aExtraData) > 0;
+}
+
+/* static */ uint8_t
+H264::NumSPS(const mozilla::MediaByteBuffer* aExtraData)
 {
   if (!aExtraData) {
-    return false;
+    return 0;
   }
 
   ByteReader reader(aExtraData);
   const uint8_t* ptr = reader.Read(5);
   if (!ptr || !reader.CanRead8()) {
-    return false;
+    return 0;
   }
-  uint8_t numSps = reader.ReadU8() & 0x1f;
-
-  return numSps > 0;
+  return reader.ReadU8() & 0x1f;
 }
 
-
 /* static */ bool
 H264::CompareExtraData(const mozilla::MediaByteBuffer* aExtraData1,
                        const mozilla::MediaByteBuffer* aExtraData2)
 {
-  // Very crude comparison.
-  return aExtraData1 == aExtraData2 || *aExtraData1 == *aExtraData2;
+  if (aExtraData1 == aExtraData2) {
+    return true;
+  }
+  uint8_t numSPS = NumSPS(aExtraData1);
+  if (numSPS == 0 || numSPS != NumSPS(aExtraData2)) {
+    return false;
+  }
+
+  // We only compare if the SPS are the same as the various H264 decoders can
+  // deal with in-band change of PPS.
+
+  SPSNALIterator it1(aExtraData1);
+  SPSNALIterator it2(aExtraData2);
+
+  while (it1 && it2) {
+    if (*it1 != *it2) {
+      return false;
+    }
+    ++it1;
+    ++it2;
+  }
+  return true;
 }
 
 #undef READUE

media/libstagefright/binding/include/mp4_demuxer/H264.h

@@ -457,6 +457,7 @@ private:
   static bool vui_parameters(BitReader& aBr, SPSData& aDest);
   // Read HRD parameters, all data is ignored.
   static void hrd_parameters(BitReader& aBr);
+  static uint8_t NumSPS(const mozilla::MediaByteBuffer* aExtraData);
 };
 
 } // namespace mp4_demuxer