Sanity check parsed QP values from H264 bitstream

webrtc/common_video/h264/h264_bitstream_parser.cc

Index: webrtc/common_video/h264/h264_bitstream_parser.cc
diff --git a/webrtc/common_video/h264/h264_bitstream_parser.cc b/webrtc/common_video/h264/h264_bitstream_parser.cc
index 048cdd2f6ea58da64b7d4b37507c2e6078a88865..e6bc946274da990dfe9867f7fdf94bad2e94df7c 100644
--- a/webrtc/common_video/h264/h264_bitstream_parser.cc
+++ b/webrtc/common_video/h264/h264_bitstream_parser.cc
@@ -19,6 +19,10 @@
 #include "webrtc/common_video/h264/h264_common.h"
 #include "webrtc/base/logging.h"
 
+namespace {
+const int kMaxAbsQpDeltaValue = 51;
+}
+
 namespace webrtc {
 
 #define RETURN_ON_FAIL(x, res)        \
@@ -251,6 +255,12 @@ H264BitstreamParser::Result H264BitstreamParser::ParseNonParameterSetNalu(
   int32_t last_slice_qp_delta;
   RETURN_INV_ON_FAIL(
       slice_reader.ReadSignedExponentialGolomb(&last_slice_qp_delta));
+  if (abs(last_slice_qp_delta) > kMaxAbsQpDeltaValue) {

[pbos-webrtc, 2016/11/29 15:31:50]

"The value of slice_qp_delta shall be limited such that SliceQPY is in the range
of −QpBdOffsetY to +51, inclusive."

Shouldn't this be between 0 and 51, not -51?

[pbos-webrtc, 2016/11/29 16:12:42]

Sorry, e.g. should this range be depending on pps_, instead of -51 and 51?

+    // Something has gone wrong, and the parsed value is invalid.
+    LOG(LS_WARNING) << "Parsed QP value out of range.";
+    return kInvalidStream;
+  }
+
   last_slice_qp_delta_ = rtc::Optional<int32_t>(last_slice_qp_delta);
   return kOk;
 }