Negotiate H264 profiles in SDP

webrtc/media/base/codec.h

 /*
  *  Copyright (c) 2004 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 136 matching lines @@
   // Creates a codec with the given parameters.
   VideoCodec(int id, const std::string& name);
   // Creates a codec with the given name and empty id.
   explicit VideoCodec(const std::string& name);
   // Creates an empty codec.
   VideoCodec();
   VideoCodec(const VideoCodec& c);
   VideoCodec(VideoCodec&& c);
   virtual ~VideoCodec() = default;
 
+  // Indicates if this codec is compatible with the specified codec. For H264,
+  // the profiles must be the same. H264 levels however are not compared.

[hta-webrtc, 2016/11/08 13:59:53]

if Codec has a Matches function, shouldn't there be an "override" below?

(overriding on a reference argument may be a problem.)

[magjed_webrtc, 2016/11/08 16:18:26]

No, this is overloading, not overriding.

+  bool Matches(const VideoCodec& codec) const;

[hta-webrtc, 2016/11/08 13:59:53]

This is actually an issue with the concept of "codec" as encompassing both an
encoder and a decoder. If we have codecs A(encoder E, decoder D) and codec
a(encoder e, decoder d), it's perfectly reasonable to have encoder E produce a
stream that is decodable by d, but encoder e can produce a stream that is not
decodable by D.

Example: A=constrained baseline, a=high profile.

Matching needs to be on an encoder vs a decoder.

[magjed_webrtc, 2016/11/08 16:18:26]

The codec here does not really encompass both an encoder and a decoder. The
codec we offer/answer over SDP happens to represent both the encoder and the
decoder, but I would say that's an SDP artifact and not built into this class.

+
   std::string ToString() const;
 
   VideoCodec& operator=(const VideoCodec& c);
   VideoCodec& operator=(VideoCodec&& c);
 
   bool operator==(const VideoCodec& c) const;
 
   bool operator!=(const VideoCodec& c) const {
     return !(*this == c);
   }
@@ skipping 49 matching lines @@
 webrtc::VideoCodecType CodecTypeFromName(const std::string& name);
 bool HasNack(const Codec& codec);
 bool HasRemb(const Codec& codec);
 bool HasTransportCc(const Codec& codec);
 bool IsCodecSupported(const std::vector<VideoCodec>& supported_codecs,
                       const VideoCodec& codec);
 
 }  // namespace cricket
 
 #endif  // WEBRTC_MEDIA_BASE_CODEC_H_