Speculative fix for division by zero in Vp8EncoderImpl.

webrtc/modules/video_coding/media_optimization.cc

 /*
  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #include "webrtc/modules/video_coding/media_optimization.h"
 
+#include <limits>
+
 #include "webrtc/base/logging.h"
 #include "webrtc/modules/video_coding/utility/frame_dropper.h"
 #include "webrtc/system_wrappers/include/clock.h"
 
 namespace webrtc {
 namespace media_optimization {
 
 struct MediaOptimization::EncodedFrameSample {
   EncodedFrameSample(size_t size_bytes,
                      uint32_t timestamp,
@@ skipping 99 matching lines @@
   return video_target_bitrate_;
 }
 
 uint32_t MediaOptimization::InputFrameRate() {
   CriticalSectionScoped lock(crit_sect_.get());
   return InputFrameRateInternal();
 }
 
 uint32_t MediaOptimization::InputFrameRateInternal() {
   ProcessIncomingFrameRate(clock_->TimeInMilliseconds());
-  return uint32_t(incoming_frame_rate_ + 0.5f);
+  uint32_t framerate = static_cast<uint32_t>(std::min<float>(
+      std::numeric_limits<uint32_t>::max(), incoming_frame_rate_ + 0.5f));
+  return framerate;

[tommi, 2017/03/10 12:55:45]

should we have a check here?  At least RTC_DCHECK(framerate)?

[stefan-webrtc, 2017/03/10 13:06:55]

framerate == 0 is handled outside this class, which I think may be reasonable
since it should be OK to compute a framerate of zero.

The issue I'm fixing here is that incoming_frame_rate_ can overflow when being
assigned to maxFramerate in VideoCodec in common_types.h, since that type was
uint8_t that wasn't too unlikely. With some bad luck that ends up being 0. :)

 }
 
 uint32_t MediaOptimization::SentFrameRate() {
   CriticalSectionScoped lock(crit_sect_.get());
   return SentFrameRateInternal();
 }
 
 uint32_t MediaOptimization::SentFrameRateInternal() {
   PurgeOldFrameSamples(clock_->TimeInMilliseconds());
   UpdateSentFramerate();
@@ skipping 126 matching lines @@
     const int64_t diff =
         incoming_frame_times_[0] - incoming_frame_times_[num - 1];
     incoming_frame_rate_ = 0.0;  // No frame rate estimate available.
     if (diff > 0) {
       incoming_frame_rate_ = nr_of_frames * 1000.0f / static_cast<float>(diff);
     }
   }
 }
 }  // namespace media_optimization
 }  // namespace webrtc