Use microsecond timestamp in cricket::VideoFrame.

webrtc/media/engine/webrtcvideoengine2.cc

 /*
  *  Copyright (c) 2014 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.
  */
 
@@ skipping 1496 matching lines @@
       cpu_restricted_counter_(0),
       number_of_cpu_adapt_changes_(0),
       source_(nullptr),
       external_encoder_factory_(external_encoder_factory),
       stream_(nullptr),
       parameters_(config, options, max_bitrate_bps, codec_settings),
       rtp_parameters_(CreateRtpParametersWithOneEncoding()),
       pending_encoder_reconfiguration_(false),
       allocated_encoder_(nullptr, webrtc::kVideoCodecUnknown, false),
       sending_(false),
-      first_frame_timestamp_ms_(0),
+      first_frame_timestamp_valid_(false),

[perkj_webrtc, 2016/04/13 05:57:06]

why this change? 

[nisse-webrtc, 2016/04/13 06:54:50]

Zero is a valid timestamp offset, we need a separate flag to tell if the offset
has been set yet or not.

[pbos-webrtc, 2016/04/13 09:56:24]

Sounds like we should use rtc::Optional then, or agree to not use rtc::Optional
elsewhere, it feels weird to mix styles in this code.

[nisse-webrtc, 2016/04/13 11:30:47]

Done. Is it correct to rely on the default constructor, to initialize it to
"unset"?

       last_frame_timestamp_ms_(0) {
   parameters_.config.rtp.max_packet_size = kVideoMtu;
   parameters_.conference_mode = send_params.conference_mode;
 
   sp.GetPrimarySsrcs(&parameters_.config.rtp.ssrcs);
   sp.GetFidSsrcs(parameters_.config.rtp.ssrcs,
                  &parameters_.config.rtp.rtx.ssrcs);
   parameters_.config.rtp.c_name = sp.cname;
   parameters_.config.rtp.extensions = rtp_extensions;
   parameters_.config.rtp.rtcp_mode = send_params.rtcp.reduced_size
@@ skipping 38 matching lines @@
   TRACE_EVENT0("webrtc", "WebRtcVideoSendStream::OnFrame");
   webrtc::VideoFrame video_frame(frame.GetVideoFrameBuffer(), 0, 0,
                                  frame.GetVideoRotation());
   rtc::CritScope cs(&lock_);
   if (stream_ == NULL) {
     // Frame input before send codecs are configured, dropping frame.
     return;
   }
 
   int64_t frame_delta_ms = frame.GetTimeStamp() / rtc::kNumNanosecsPerMillisec;
+
   // frame->GetTimeStamp() is essentially a delta, align to webrtc time
-  if (first_frame_timestamp_ms_ == 0) {
+  if (!first_frame_timestamp_valid_) {
     first_frame_timestamp_ms_ = rtc::Time() - frame_delta_ms;
+    first_frame_timestamp_valid_ = true;
   }
 
   last_frame_timestamp_ms_ = first_frame_timestamp_ms_ + frame_delta_ms;
+
   video_frame.set_render_time_ms(last_frame_timestamp_ms_);
   // Reconfigure codec if necessary.
   SetDimensions(video_frame.width(), video_frame.height());
   last_rotation_ = video_frame.rotation();
 
   // Not sending, abort after reconfiguration. Reconfiguration should still
   // occur to permit sending this input as quickly as possible once we start
   // sending (without having to reconfigure then).
   if (!sending_) {
     return;
   }
 
   stream_->Input()->IncomingCapturedFrame(video_frame);
 }
 
 void WebRtcVideoChannel2::WebRtcVideoSendStream::SetSource(
     rtc::VideoSourceInterface<cricket::VideoFrame>* source) {
   TRACE_EVENT0("webrtc", "WebRtcVideoSendStream::SetSource");
   RTC_DCHECK(thread_checker_.CalledOnValidThread());
 
   if (!source && !source_)
     return;
   DisconnectSource();
 
   {
     rtc::CritScope cs(&lock_);
 
     // Reset timestamps to realign new incoming frames to a webrtc timestamp. A
     // new capturer may have a different timestamp delta than the previous one.
-    first_frame_timestamp_ms_ = 0;
+    first_frame_timestamp_valid_ = false;
 
     if (source == NULL) {
       if (stream_ != NULL) {
         LOG(LS_VERBOSE) << "Disabling capturer, sending black frame.";
         webrtc::VideoFrame black_frame;
 
         CreateBlackFrame(&black_frame, last_dimensions_.width,
                          last_dimensions_.height, last_rotation_);
 
         // Force this black frame not to be dropped due to timestamp order
@@ skipping 945 matching lines @@
         rtx_mapping[video_codecs[i].codec.id] !=
             fec_settings.red_payload_type) {
       video_codecs[i].rtx_payload_type = rtx_mapping[video_codecs[i].codec.id];
     }
   }
 
   return video_codecs;
 }
 
 }  // namespace cricket