Simplify {,Set}UlpfecConfig interface.

webrtc/modules/rtp_rtcp/include/rtp_rtcp.h

 /*
  *  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.
  */
 
@@ skipping 435 matching lines @@
   // indication.
   // This API shall be called before transmision of an RTP packet to ensure
   // that the |level| part of the extended RTP header is updated.
   // return -1 on failure else 0.
   virtual int32_t SetAudioLevel(uint8_t level_dbov) = 0;
 
   // **************************************************************************
   // Video
   // **************************************************************************
 
-  // Turn on/off ULPFEC.
-  virtual void SetUlpfecConfig(bool enabled,
-                               int red_payload_type,
+  // Set RED and ULPFEC payload types. A payload type of -1 means that the
+  // corresponding feature is turned off. Note that we DO NOT support enabling
+  // ULPFEC without enabling RED. However, we DO support enabling RED without
+  // enabling ULPFEC. This is due to an RED/RTX workaround, where the receiver
+  // assumes that RTX packets carry RED if RED has been configured in the SDP,
+  // regardless of what RTX payload type mapping was negotiated in the SDP.
+  // TODO(brandtr): Update this comment when we have removed the RED/RTX
+  // send-side workaround, i.e., when we do not support enabling RED without
+  // enabling ULPFEC.
+  virtual void SetUlpfecConfig(int red_payload_type,
                                int ulpfec_payload_type) = 0;
 
   virtual int32_t SetFecParameters(const FecProtectionParams* delta_params,
                                    const FecProtectionParams* key_params) = 0;
 
   // Set method for requestion a new key frame.
   // Returns -1 on failure else 0.
   virtual int32_t SetKeyFrameRequestMethod(KeyFrameRequestMethod method) = 0;
 
   // Sends a request for a keyframe.
   // Returns -1 on failure else 0.
   virtual int32_t RequestKeyFrame() = 0;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_RTP_RTCP_INCLUDE_RTP_RTCP_H_