Correcting the amount of padding when send side bwe includes RTP overhead.

webrtc/modules/rtp_rtcp/source/rtp_sender.cc

Index: webrtc/modules/rtp_rtcp/source/rtp_sender.cc
diff --git a/webrtc/modules/rtp_rtcp/source/rtp_sender.cc b/webrtc/modules/rtp_rtcp/source/rtp_sender.cc
index 52b0891ea7390bcd7f8f04c3df56bd86b99a573f..7e0852fe78a23ba579b81bfa7c04c3c81692eff6 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_sender.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtp_sender.cc
@@ -455,33 +455,43 @@ size_t RTPSender::TrySendRedundantPayloads(size_t bytes_to_send,
   int bytes_left = static_cast<int>(bytes_to_send);
   while (bytes_left > 0) {
     std::unique_ptr<RtpPacketToSend> packet =
-        packet_history_.GetBestFittingPacket(bytes_left);
+        packet_history_.GetBestFittingPacket(bytes_left,
+                                             send_side_bwe_with_overhead_);
     if (!packet)
       break;
-    size_t payload_size = packet->payload_size();
+    // When WebRTC-SendSideBwe-WithOverhead is enabled, the padding budget
+    // includes overhead.
+    const size_t used_bytes = send_side_bwe_with_overhead_
+                                  ? packet->size()
+                                  : packet->size() - packet->headers_size();
     if (!PrepareAndSendPacket(std::move(packet), true, false, pacing_info))
       break;
-    bytes_left -= payload_size;
+    bytes_left -= used_bytes;
   }
   return bytes_to_send - bytes_left;
 }
 
 size_t RTPSender::SendPadData(size_t bytes,
                               const PacedPacketInfo& pacing_info) {
-  size_t padding_bytes_in_packet;
+  // Always send full padding packets. This is accounted for by the
+  // RtpPacketSender, which will make sure we don't send too much padding even
+  // if a single packet is larger than requested.
+  // We do this to avoid frequently sending small packets on higher bitrates.
+  size_t padding_bytes_in_packet =
+      std::min(MaxPayloadSize(), kMaxPaddingLength);
+
   if (audio_configured_) {
     // Allow smaller padding packets for audio.
+
+    // When WebRTC-SendSideBwe-WithOverhead is enabled, the padding budget
+    // includes overhead.
+    const size_t padding_bytes_if_one_packet =
+        send_side_bwe_with_overhead_ ? bytes - RtpHeaderLength() : bytes;
     padding_bytes_in_packet =
-        std::min(std::max(bytes, kMinAudioPaddingLength), MaxPayloadSize());
-    if (padding_bytes_in_packet > kMaxPaddingLength)
-      padding_bytes_in_packet = kMaxPaddingLength;
-  } else {
-    // Always send full padding packets. This is accounted for by the
-    // RtpPacketSender, which will make sure we don't send too much padding even
-    // if a single packet is larger than requested.
-    // We do this to avoid frequently sending small packets on higher bitrates.
-    padding_bytes_in_packet = std::min(MaxPayloadSize(), kMaxPaddingLength);
+        std::min(padding_bytes_in_packet,
+                 std::max(padding_bytes_if_one_packet, kMinAudioPaddingLength));
   }
+
   size_t bytes_sent = 0;
   while (bytes_sent < bytes) {
     int64_t now_ms = clock_->TimeInMilliseconds();
@@ -566,6 +576,7 @@ size_t RTPSender::SendPadData(size_t bytes,
     PacketOptions options;
     bool has_transport_seq_num =
         UpdateTransportSequenceNumber(&padding_packet, &options.packet_id);
+
     padding_packet.SetPadding(padding_bytes_in_packet, &random_);
 
     if (has_transport_seq_num) {
@@ -576,7 +587,10 @@ size_t RTPSender::SendPadData(size_t bytes,
     if (!SendPacketToNetwork(padding_packet, options, pacing_info))
       break;
 
-    bytes_sent += padding_bytes_in_packet;
+    // When WebRTC-SendSideBwe-WithOverhead is enabled, the padding budget
+    // includes overhead.
+    bytes_sent += send_side_bwe_with_overhead_ ? padding_packet.size()
+                                               : padding_packet.padding_size();

[stefan-webrtc, 2017/04/04 08:13:38]

Maybe for consistency use: packet->size() - packet->headers_size()?

[minyue-webrtc, 2017/04/11 09:35:14]

I would rather do padding_size + headers_size

I hope to avoid using size(), everywhere if possible, since it is not clear by
its name.

[danilchap, 2017/04/11 14:25:18]

personally prefer size() function too:
size_t packet_size = packet->size();

But may be because I remember what that function do. [full size of the packet
RTPSender aware of, i.e. include rtp overhead, exclude udp/crypto overheads].

[minyue-webrtc, 2017/04/11 14:30:51]

You are right here. I realized that we should include transport overhead here as
well. Per offline discussion with Stefan, I may do it in a follow up CL, since
current change is already an improvement,

     UpdateRtpStats(padding_packet, over_rtx, false);
   }