[Cast] Repair receiver playout time calculations and frame skip logic.

media/cast/cast_defines.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_CAST_CAST_DEFINES_H_
 #define MEDIA_CAST_CAST_DEFINES_H_
 
 #include <stdint.h>
 
+#include <limits>
 #include <map>
 #include <set>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/logging.h"
 #include "base/time/time.h"
 #include "media/cast/transport/cast_transport_config.h"
 
 namespace media {
@@ skipping 108 matching lines @@
          ((delay_fraction & 0xFFFF0000) >> 16);
 }
 
 inline base::TimeDelta ConvertFromNtpDiff(uint32 ntp_delay) {
   uint32 delay_ms = (ntp_delay & 0x0000ffff) * 1000;
   delay_ms >>= 16;
   delay_ms += ((ntp_delay & 0xffff0000) >> 16) * 1000;
   return base::TimeDelta::FromMilliseconds(delay_ms);
 }
 
-inline void ConvertTimeToFractions(int64 time_us,
+inline void ConvertTimeToFractions(int64 ntp_time_us,
                                    uint32* seconds,
                                    uint32* fractions) {
-  DCHECK_GE(time_us, 0) << "Time must NOT be negative";
-  *seconds = static_cast<uint32>(time_us / base::Time::kMicrosecondsPerSecond);
+  DCHECK_GE(ntp_time_us, 0) << "Time must NOT be negative";
+  const int64 seconds_component =
+      ntp_time_us / base::Time::kMicrosecondsPerSecond;
+  // NTP time will overflow in the year 2036.  Also, make sure unit tests don't
+  // regress and use an origin past the year 2036.  If this overflows here, the
+  // inverse calculation fails to compute the correct TimeTicks value, throwing
+  // off the entire system.

[hubbe, 2014/05/19 17:52:20]

Maybe put a DCHECK(ntp_time_us is less than the year 2035) to auto-break this
one year before the deadline? :)

Hopefully this code is dead and buried by then, but if it not, we could at least
give the poor schmuck who is working on it then a year to fix it...

[miu, 2014/05/23 03:09:01]

Done.

+  CHECK(seconds_component <= std::numeric_limits<uint32>::max());
+  *seconds = static_cast<uint32>(seconds_component);
   *fractions = static_cast<uint32>(
-      (time_us % base::Time::kMicrosecondsPerSecond) * kMagicFractionalUnit);
+      (ntp_time_us % base::Time::kMicrosecondsPerSecond) *
+          kMagicFractionalUnit);
 }
 
 inline void ConvertTimeTicksToNtp(const base::TimeTicks& time,
                                   uint32* ntp_seconds,
                                   uint32* ntp_fractions) {
   base::TimeDelta elapsed_since_unix_epoch =
       time - base::TimeTicks::UnixEpoch();
 
   int64 ntp_time_us =
       elapsed_since_unix_epoch.InMicroseconds() +
@@ skipping 67 matching lines @@
   base::TimeTicks time_sent_;
   uint32 rtp_timestamp_;
 
   DISALLOW_COPY_AND_ASSIGN(RtpSenderStatistics);
 };
 
 }  // namespace cast
 }  // namespace media
 
 #endif  // MEDIA_CAST_CAST_DEFINES_H_