Use RtcpPacket to send REMB in RtcpSender

webrtc/modules/rtp_rtcp/source/rtcp_sender.cc

Index: webrtc/modules/rtp_rtcp/source/rtcp_sender.cc
diff --git a/webrtc/modules/rtp_rtcp/source/rtcp_sender.cc b/webrtc/modules/rtp_rtcp/source/rtcp_sender.cc
index e118fb262c4e9b539f51f385a0897be3dbe2a8bc..5ebd4a895d54cced9e03681930485c1eaf2e90e9 100644
--- a/webrtc/modules/rtp_rtcp/source/rtcp_sender.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtcp_sender.cc
@@ -638,47 +638,15 @@ RTCPSender::BuildResult RTCPSender::BuildRPSI(RtcpContext* ctx) {
 }
 
 RTCPSender::BuildResult RTCPSender::BuildREMB(RtcpContext* ctx) {
-  // sanity
-  if (ctx->position + 20 + 4 * remb_ssrcs_.size() >= IP_PACKET_SIZE)
-    return BuildResult::kTruncated;
-
-  // add application layer feedback
-  uint8_t FMT = 15;
-  *ctx->AllocateData(1) = 0x80 + FMT;
-  *ctx->AllocateData(1) = 206;
+  rtcp::Remb remb;
+  remb.From(ssrc_);
+  for (uint32_t ssrc : remb_ssrcs_)
+    remb.AppliesTo(ssrc);
+  remb.WithBitrateBps(remb_bitrate_);
 
-  *ctx->AllocateData(1) = 0;
-  *ctx->AllocateData(1) = static_cast<uint8_t>(remb_ssrcs_.size() + 4);
-
-  // Add our own SSRC
-  ByteWriter<uint32_t>::WriteBigEndian(ctx->AllocateData(4), ssrc_);
-
-  // Remote SSRC must be 0
-  ByteWriter<uint32_t>::WriteBigEndian(ctx->AllocateData(4), 0);
-
-  *ctx->AllocateData(1) = 'R';
-  *ctx->AllocateData(1) = 'E';
-  *ctx->AllocateData(1) = 'M';
-  *ctx->AllocateData(1) = 'B';
-
-  *ctx->AllocateData(1) = remb_ssrcs_.size();
-  // 6 bit Exp
-  // 18 bit mantissa
-  uint8_t brExp = 0;
-  for (uint32_t i = 0; i < 64; i++) {
-    if (remb_bitrate_ <= (0x3FFFFu << i)) {
-      brExp = i;
-      break;
-    }
-  }
-  const uint32_t brMantissa = (remb_bitrate_ >> brExp);
-  *ctx->AllocateData(1) =
-      static_cast<uint8_t>((brExp << 2) + ((brMantissa >> 16) & 0x03));
-  *ctx->AllocateData(1) = static_cast<uint8_t>(brMantissa >> 8);
-  *ctx->AllocateData(1) = static_cast<uint8_t>(brMantissa);
-
-  for (size_t i = 0; i < remb_ssrcs_.size(); i++)
-    ByteWriter<uint32_t>::WriteBigEndian(ctx->AllocateData(4), remb_ssrcs_[i]);
+  PacketBuiltCallback callback(ctx);
+  if (!callback.BuildPacket(remb))
+    return BuildResult::kTruncated;
 
   TRACE_EVENT_INSTANT0(TRACE_DISABLED_BY_DEFAULT("webrtc_rtp"),
                        "RTCPSender::REMB");